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Improved Preservation and Early Stage Processing of Australian Crocodile Skins

A report for the Rural Industries Research and Development Corporation

by Stephen Hawkins and Chi Huynh CSIRO Textile and Fibre Technology

December 2004

ISBN 1 74151 073 2 ISSN 1440-6845

‘Improved Preservation and Early Stage Processing of Australian Crocodile Skins’ Publication No. 04/164 Project No. CWT-3A

The views expressed and the conclusions reached in this publication are those of the author and not necessarily those of persons consulted. RIRDC shall not be responsible in any way whatsoever to any person who relies in whole or in part on the contents of this report.

This publication is copyright. However, RIRDC encourages wide dissemination of its research, providing the Corporation is clearly acknowledged. For any other enquiries concerning reproduction, contact the Publications Manager on phone 02 6272 3186.

Researcher Contact Details Dr. Stephen C Hawkins CSIRO Textile and Fibre Technology, PMB 10, Clayton MDC, Victoria 3168

Phone: 03 9545 2364 Fax: 03 9545 2363 Email: [email protected]

In submitting this report, the researcher has agreed to RIRDC publishing this material in its edited form.

RIRDC Contact Details Rural Industries Research and Development Corporation Level 1, AMA House 42 Macquarie Street BARTON ACT 2600 PO Box 4776 KINGSTON ACT 2604

Phone: 02 6272 4819 Fax: 02 6272 5877 Email: [email protected] Website: http://www.rirdc.gov.au

Published in December 2004 Printed on environmentally friendly paper by Canprint

Foreword

The skin of the Australian saltwater crocodile, (Crocodylus porosus) reputedly produces the best quality crocodile leather in the world. Crocodiles have been farmed in Australia since 1972 to supply the international demand for these skins, and hence reduce the pressure from poaching of wild animals. Australia currently produces around 10,000 skins per year which can be valued at up to around $600 each. Farming also produces meat and generates considerable tourism revenue in tropical Australia. Trade in crocodile products is strictly controlled under the CITES regulations.

Crocodile skin is easily damaged by poor husbandry of the live animal or mishandling of the skins after slaughter, resulting in scratches, infections, staining and microbial degradation and thus substantial loss of value. The project reported here describes research to improve the post-slaughter early stage processing and preservation of skins in order to maintain them in optimum condition. Processes were developed to suit the unique characteristics of crocodile skins, and the particular trading and processing requirements used in this industry, where most skins are exported to specialist tanneries in Asia and Europe.

This research is supported by RIRDC and CSIRO with additional support from Koorana Crocodile Farm and was conducted by CSIRO. It complements previous and current research supported by RIRDC in areas of crocodile husbandry and breeding to ensure the sustainability of this important rural industry.

This project was funded from RIRDC Core Funds which are provided by the Australian Government. This report, an addition to RIRDC’s diverse range of over 1000 research publications, forms part of our New Animal Products R&D program, which aims to accelerate the development of viable new animal industries.

Most of our publications are available for viewing, downloading or purchasing online through our website:

• downloads at www.rirdc.gov.au/fullreports/index.html • purchases at www.rirdc.gov.au/eshop

Simon Hearn Managing Director Rural Industries Research and Development Corporation

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Contents

Foreword...... iii Executive Summary...... v 1. Introduction...... 1 2. Fleshing...... 3 2.1 Background and Objectives...... 3 2.2 Methodology and Experiment...... 3 2.3 Results and Discussion ...... 3 2.4 Conclusions and Recommendations ...... 4 3. Preservation and Storage ...... 5 3.1 Background and Objectives...... 5 3.2 Methodology...... 6 3.3 Experimental...... 7 3.4 Results and Discussion ...... 10 3.5 Conclusions and Recommendations ...... 16 4. Shrinkage...... 18 4.1 Background and Objectives...... 18 4.2 Methodology...... 19 4.3 Experimental...... 19 4.4 Results and Discussion ...... 21 4.5 Conclusions and Recommendations ...... 29 5. Fault Identification ...... 31 5.1 Background and Objectives...... 31 5.2 Methodology...... 31 5.3 Results and Discussion ...... 31 5.4 Conclusions and Recommendations ...... 34 6. Quality Management ...... 35 6.1 Background and Objectives...... 35 6.2 Observations and Recommendations...... 36 7. Conclusions...... 39 Appendices...... 44 Appendix 1 Short-Term Preservation Procedure for C. porosus Skins...... 44 Appendix 2. Long-Term Preservation Procedure for C. porosus Skins...... 45 Appendix 3. Sources ...... 46

Executive Summary

The Australian Saltwater Crocodile (Crocodylus porosus) is the largest crocodilian species and reputedly produces the best quality crocodile leather in the world. High demand for skins and excessive poaching greatly reduced their numbers and resulted in the establishment of crocodile farming in Australia from 1972, which is credited with reducing the threat of extinction of C. porosus in the wild.

The value of crocodile skins is determined by their width at the third raised scute (scale) below the front legs, and by the grading outcome with 25% of the value being lost per grade level. Although the skin attracts prices of the order of US$9 per centimetre of width for first grade, or US$360 for a 40 cm skin, skins are increasingly downgraded due to faults. An overall decline by an average of one grade represents a loss of around $1 million to the industry.

The initial objectives of the project were to investigate fleshing (removal of residual meat and fat from the skin), and preservation and storage. However two additional issues arose that warranted attention (shrinkage and fault identification). Finally, quality management issues were surveyed and general problems identified for further consideration.

The fleshing operation was estimated to cost approximately $12 per skin for labour plus capital and other operating costs, involving the use of a very high pressure water jet and sharp implements on a valuable skin. The project objective for the fleshing operation was to reduce labour costs by at least 50%, whilst ensuring that the methodology was not damaging the skin and preservation was maintained. As a result of this study, it was concluded that there was no benefit from fleshing and this activity was eliminated, saving 100% of the cost and risk of fleshing.

The overall objective with respect to fleshing, preservation and storage was to improve the average grade of the skins by at least 10 percentage points and to eliminate these operations as a cause of downgrading. Failure to store the preserved skins adequately gives rise to damage, staining and biological damage. A short term preservation treatment using cold 60% brine solution was recommended for holding the skins for up to 5 days. Long term preservation for up to 4 months at 30oC then only entails addition of a commercial biocide to the brine.

Individual packing in sealed bags is highly recommended as it keeps the skins in excellent condition and simplifies handling. However use of vacuum is not supported as it causes slightly more creasing and scale indentation, cannot be guaranteed to persist because of leaks and punctures, and is of no clear benefit for preservation. Folding of the skins such that creases are formed across the line measurement used by the buyer makes such measurement more inconvenient and may influence the result. It was therefore recommended the traditional way of folding be changed to keep this line flat.

During the course of research it became apparent that the crocodile skins underwent contractions in width and hence value of about 10% to the detriment of the producer. The objective was set to achieve a 5 percentage point average increase in width accepted by the processor and with no negative pricing signals. The cause was identified as exposure to solid salt or saturated brine. Some reduction in width appears inevitable but use of 60% brine with appropriate preservatives was found to limit this to around 5% or less.

The blemishes on crocodile skins, particularly in the valuable main panel area of the belly, from collar to cloaca and flank to flank, are used to estimate the value of the skin as finished leather and a grade given accordingly. In order to make changes that are cost-effective and successful, the producer must be in a position to accurately identify blemishes and predict their impact on the finished leather value. Therefore, the objective was made to capture a pictorial record as a reference catalogue for producers. The exercise highlighted the problems and logistic requirements for a future project. Initial results were well received by the industry.

During the project, the number of first grade skins increased from 13% to 32% of the total with concomitant decrease in the lowest grade, although how much of this is attributable directly or indirectly to the project is unclear as it was conducted against a background of other changes.

The ISO 9000 standard was used as a template in briefly reviewing the quality management requirements in crocodile skin production. It was found that crocodile farming is a complex activity with many characteristics that would make it very suited to a quality management style of control and organisation. In order to make steady, verifiable improvement to the quality of production, the existing processes and procedures should be stabilised, preferably in their simplest acceptable form, and no further changes made. This can most easily be done through the ISO 9000 documentation template. Once documented, no change should occur either to simplify the process, to solve problems or to improve quality, unless it has been analysed and verified. Once it has, the documentation should be updated to a new version and the old version withdrawn.

During the course of the project, it was only possible to utilise a very limited number of skins and at isolated points in time. Further developmental work is recommended to optimise the various process developments. In accord with the quality management approach, it is most important that any changes made as a result of recommendations contained within this report be fully verified for the particular circumstances to which they are to be applied prior to full implementation.

1. Introduction

The main farm income is derived from crocodile skins for the fashion leather industry, although crocodile farming also produces meat and generates significant tourism revenue. However, the market share and price for C. porosus skins is declining due, in part, to increased production overseas of other species with lower production costs, and to declining quality as measured by the skin grades being achieved. The small scale of production and the limited capabilities for further processing in Australia may also be factors contributing to the decline.

C. porosus is a slow-growing, aggressive animal requiring relatively high expenditure to farm and process. Although the skin attracts prices of the order of US$9 per centimetre of width for first grade, or US$360 for a 40 cm skin, profit margins are not large and are subject to drastic variability. In addition to changes in the US$ price offered by buyers, the amount received in A$ is subject to exchange rate fluctuations. Due to the ease with which faults can be seen in the raw skin, lower grade skins are heavily discounted. Traditionally, each downgrade has cost 25% of the potential value of a skin with 1st grade earning 100%, 2nd grade 75% etc. However the grade premium is at times even higher with some buyers refusing to take 2nd or lower grades at all.

Quantifying the loss in value from downgrading is problematic due to fluctuating exchange rates and prices and industry confidentiality. However as an indication, in the last 10 years, the proportion of 1st grade C. porosus skins being produced has reportedly fallen from about 50% to 20%. For an industry production currently of approximately 10,000 skins with a value as first grades of around A$600 each, the decline in first grades alone is a loss of around $0.4m pa and potentially well over $1m for all grades. This fall in grade quality has both reduced returns and moved C. porosus skins more into competition with lower quality and cost species. Differentiation, cost reduction and increased quality are thus areas where the Australian industry can make significant improvements.

Of the various causes of poor skin quality or productivity, the animal-husbandry problems such as poor fertility, growth and nutrition; skin damage from sharp edges and fighting; skin infections etc. have been or are being solved. For example, individual ‘grow-out’ pens are currently being trialled in the industry, to reduce skin cuts, scratches and scars before slaughter. Costs of skin processing, and damage to skins after slaughter, for example from fleshing and poor preservation, were identified as areas still to be addressed.

The processing of crocodiles entails the sequence of operations:

• stunning (some producers do not stun prior to slaughter) • slaughter (by severing of spinal chord) • disinfection (skin is swabbed with disinfectant according to food safety guidelines) • chilling (carcase is hung in cool room usually overnight to chill and bleed before skinning) • skinning (skin is carefully removed in cool, food-standard abattoir) • meat processing (meat is packed and chilled according to standards and requirements) and • skin processing, involving − short term preservation − trimming − long term preservation − grading and measurement − packing, and storage until despatch

To add value to their skins, crocodile skin producers often ‘flesh’ them at the ‘short-term preservation’ or ‘trimming’ stage to remove the adhering fat, muscle and connective tissue. This is an essential operation but is usually carried out by processors (tanners), not producers, to aid in tanning and dyeing. Fleshing of the raw skin can make preservation simpler, increase skin area, make grading more certain and reduce transportation costs, but for producers it is a difficult, labour intensive operation that exposes the skins to damage and hence is amenable to improvement.

Effective preservation is critical because if poorly preserved, crocodile skins can quickly deteriorate in the warm humid environment in which they are produced. Putrefaction and the action of autolytic enzymes naturally present in the skin can cause scales to fall off (“scale slip”) and the resulting leather to be scuffed, weak or even perforated. The development of rapid and effective short and long term preservation procedures that are appropriate to the Australian crocodile farm environment is a requisite to improving quality. An important component of preservation is storage under appropriate conditions.

The initial objectives of the project were to investigate fleshing, and preservation and storage. However two additional issues, shrinkage and fault identification, arose that warranted attention. Crocodile skins are priced according to a measurement in centimetres made across the width at the third scute (raised back scale), approximating to 8 cm below the front legs for a 40 cm wide skin. The width measurement is made, after the skin is preserved, by the producer and then on receipt by the buyer with the latter usually taking precedence for pricing. It became clear that this width is highly unstable, usually to the disadvantage of the producer due to shrinkage of up to 10% and occasionally more. Research was conducted to identify the causes of the width instability and methods of preventing it to ensure the producer received maximum return.

C. porosus skins are unusual compared with sheep skins and cattle hides (which comprise the vast majority of the tanning industry raw material) in that the grain surface of the raw skin in the prime cutting area (the belly area from collar to cloaca and flank to flank, from which the highest value items are made) can be clearly seen and graded according to the quality of leather it will make. This leads both to the high grade premium and losses due to faults, and also to an opportunity to influence the quality prior to slaughter. However it was apparent that there was some uncertainty about the cause and identity of various blemishes seen in the skin of the live animal and their significance in the final leather. Therefore experiments were conducted to analyse blemishes in the raw skin and track their appearance through to finished leather and develop a pictorial guide.

Finally, quality management issues were surveyed and general problems identified for further consideration. Issues of process specification, changes to operations based on firm evidence, tracking of skins and outcomes etc. were examined.

The following report is organised into the five topics (1. Fleshing; 2. Preservation and Storage; 3. Shrinkage; 4. Tracking; and 5. Quality) noted above, with objectives, methodology, results and discussion, and conclusions and recommendations given for each topic. Conclusions and recommendations are summarised together in the final chapter. The project was conducted with support from the Rural Industries Research and Development Corporation (RIRDC) and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) division, Textile and Fibre Technology (TFT), in collaboration with Koorana Crocodile Farm (KCF), Rockhampton, Queensland. It should be noted that many experiments ran concurrently, extended over a number of months and encompassed a range of variables and objectives. As a result, the results presented may be out of time-order so that the variables can be described in a coherent fashion.

2. Fleshing

2.1 Background and Objectives

The fleshing operation was considered by the collaborating producer to be important in preparing crocodile skins for preservation and sale. It entailed hand trimming and scraping, and use of a very high pressure water jet, incurring a labour cost of approximately $12 per skin plus capital and other operating costs. In addition to the evident danger of using sharp implements on a valuable skin and the delay in preservation the process required, there was also a suggestion that the high pressure water spray could cause weakening or looseness (sponginess) of the final leather. The objective for the fleshing operation was therefore to reduce labour costs by at least 50%, whilst ensuring that the methodology was not damaging the skin and preservation was maintained.

2.2 Methodology and Experiment

The planned methodology was to:

• survey the current fleshing method and acquire baseline data • acquire a high pressure water jet and establish a laboratory fleshing operation , to the standard determined in consultation with the producer to be most cost effective, to provide the bench-mark against which alternatives will be tested prior to industry trialling • investigate alternative methods of fleshing, including the testing of a range of commercially available enzymes, hand fleshing, high-pressure spray and mechanical fleshing either alone or in concert, and • compare the leather quality of skins using the most promising fleshing methods. The method(s) giving the most beneficial combination of cost, efficiency and quality to be trialled and, if satisfactory, implemented.

2.3 Results and Discussion

An initial survey found that:

• each crocodile skin required 50 to 65 person-minutes to trim, clean and fully flesh • initial preservation was interrupted or delayed for up to 2 hours • final preservation was delayed by up to one day • score marks from sharp tools were occasionally made in the skin although no perforations were noted and • fleshed skins were clearly turgid although no damage was immediately apparent.

However, it was also observed that the skins as removed from the carcases were very clean and largely free from meat and fat and what was present did not significantly affect preservation, area, or shipping weight. As grading was wholly based on the quality of the grain (scale) surface, the presence of small amounts of fat and meat did not influence this assessment. Therefore it was determined that, although fleshing produced a cosmetic improvement to the skin, no direct benefit was or could be accrued to the producer.

The question remained as to whether the purchaser of the skins received some benefit and, more importantly, provided a premium payment to the producer for the fleshing. Although fleshing was believed to be necessary and that some element of the payment received from buyers was for this, no actual premium could be quantified. The difficulty in pursuing this question lay in the fact that buyers could not be expected to give a disinterested reply, and that as all skins are sold to foreign buyers, there was considerable scope for misinterpretation of the question or the answer. It was

therefore decided to visit several reptile processors (tanneries) in Japan using the good offices of the producer to obtain access and to conduct a number of experiments as reported herein.

It was found in relation to fleshing that:

• the main Japanese processor visited received the skins of a number of crocodilian species from around the world, including Australia • the skins were normally not fleshed by producers and foreign skins clearly had more fat and meat on than skins produced by the Australian operation (prior to fleshing) • the processor routinely soaked and fleshed all skins received, regardless of their previous treatment, and • the processor received no benefit and paid no premium to producers for fleshing of skins.

2.4 Conclusions and Recommendations

As a result of the visit to the processors, it was concluded that there was no benefit and considerable cost and risk to the Australian skin producer in fleshing the crocodile skins. It was therefore recommended that all fleshing operations cease and that trimming be confined to ensuring clean and careful removal of the skin from the carcase. This action eliminated 100% of the cost and risk of fleshing.

More generally, it is clear that all operations should be reviewed periodically to determine whether they are necessary or provide a net benefit to the producer. Decisions should be made on the basis of good quality information, either from experimentation with appropriate controls, or from careful and thorough gathering of market intelligence.

3. Preservation and Storage

3.1 Background and Objectives

The principle reason for crocodile farming to exist in Australia is to produce crocodile skins to satisfy market demand for C. porosus leather. It is therefore absolutely essential that, in the first instance, the quality of skin on the live animal prior to slaughter is as high as it can be, and second that that quality be maintained right through to the finished leather. It must be borne in mind that the quality of the skin can still be improved up to the point of slaughter, but only maintained or degraded from slaughter onwards. Also, that by virtue of their large surface area and pre-existing heavy microbial contamination, skins are at least as susceptible to putrefaction as is meat.

As soon as the animal is slaughtered, there is both loss of immune response and development of autolytic protein breakdown which render the skin very susceptible to microbial damage. Microbial attack commences immediately, continues at low temperatures, and is cumulative and accelerating. If not preserved adequately, severe damage will occur to skins held at 30oC for several hours (either continuously or in total with intervening cool storage) or up to several days at 5oC.

Damage may be indicated by scale slip (Figure 1), discolouration such as ‘red heat’ (Fig. 2), or the smell but there may be no signs at all until the end of tannage and finishing when the grain surface is found to be dull, discoloured or scuffed, (Fig. 3) resulting in a heavy loss in value for the tanner. Usually bacterial attack occurs first, resulting in scale slip and odour. Fungal attack is slower and results in staining, and surface erosion, but is much more difficult to prevent. To avoid or minimise damage, skins should be preserved against microbial attack as soon as possible, preferably commencing before skinning, with a preservative that is suited to the task and applied correctly.

Figure 1. Scale slip Figure 2. ‘Red heat’ Figure 3. Scuffed grain from bacterial contamination microbial attack

Untanned skins are also susceptible to heat, with damage occurring immediately on contact with any surface over 60oC, or on prolonged contact at 50oC. These temperatures can easily be reached by objects left in the sun, by operating machinery and even by the friction of hard rubbing. Contact with hot water and steam are also common sources of heat damage. Care must be taken to ensure that fresh skins do not dry out before preservation, especially on hot, windy days. Uncontrolled drying will cause brittleness and preservation problems and difficulties in tanning uniformly.

Short term preservation processes are applied, usually starting before the carcase is skinned and proceeding through to several days after, to protect skins and allow them to be handled for grading, trimming, measurement or brief transport. If skins are to be held for more than about 4 days before processing to leather, it is necessary to apply a long-term preservation treatment. This should aim to preserve the skins for the anticipated time and conditions in storage including an appropriate safety margin in case of delay or high temperatures. The short-term preservation should contribute to the long-term preservation process, rather than having to be reversed or discarded.

Long-term preservation has traditionally entailed the use of extremely large amounts of salt without other preservatives. However, halophilic bacteria and fungi are able to grow in these conditions and damage skins, and the salt adds weight, and makes grading and measurement more difficult. The halophilic bacteria commonly appear as red or purple stains (“red heat”). Although these bacteria are not themselves severely damaging, they are a clear sign of preservation failure and that other more damaging but less obvious organisms are likely to be present. Salted skins are routinely stored in a cool room because the salt alone is an inadequate preservative.

During storage, preserved skins are still susceptible to damage from insect and rodent attack, overheating, or contamination from detergents, chemicals and solvents. Water can dissolve and remove or redistribute the preservative. Dirt or contamination can cause preservatives to break down prematurely or to be rendered ineffective. Iron or rust particles coming into contact with the skin cause a brown iron stain that is extremely difficult to remove or hide and which can react with tanning agents to form dark blue or black patches. In summary, skins should be undamaged, cool, clean, protected and preserved.

It is important that preservation be appropriate, adequate and efficient and that the storage conditions do not cause deterioration or damage. The preservative must be safe to handle by the producer and by the processor, and not interfere with the tanning process. Various countries impose import bans on leather containing particular chemicals and so it is important to ensure that only currently acceptable preservatives are used.

The overall objective with respect to fleshing, preservation and storage was to improve the average grade of the skins through improved preservation and fleshing and to eliminate these operations as a cause of downgrading and increase the proportion of first grade skins with concomitant improvements in other grades. An increase in the proportion of first grades from 20 to only 30% would amount to a benefit of about $175,000 to the industry based on the traditional grading discount for seconds. Additional objectives were to reduce the labour component of the operations, reduce weight and waste, and identify an improved preservation process.

Packing of the skins arose as an issue in response to the suggestions that vacuum packing resulted in improved presentation and preservation, and that an alternative folding pattern could improve or at least maintain the measured width of the skins. Conventional folding produces a pair of vertical creases where the flanks are folded into the middle. Subsequent width measurement is across the creases and may be reduced in consequence. Vacuum packing of folded skins was thought to carry the risk of permanently creasing them.

3.2 Methodology

The approach taken to improving the preservation and storage of crocodile skins was to identify critical points of damage and of potential intervention and control. The existing operation of the collaborating producer was surveyed and data collected, together with comments from other producers, and an interim preservation and storage protocol implemented. It was anticipated that this would need to be adapted to integrate with the fleshing operation, as this was being developed, to give an efficient coordinated process from slaughter to export. However, as noted above, fleshing was eliminated whilst other problems, most notably shrinkage, were identified that required study and integration with the preservation process.

In addition to the requirements that the preservation process maintain the quality of the skin through to finished leather and be acceptable from the perspectives of efficiency and safety, crocodile skins impose an additional constraint that cattle hides and sheep skins do not. Upon receipt and prior to any soaking or processing by the purchaser, crocodile skins must be in a condition to be measured and graded as accurately as possible. Traditional methods where skins are heavily coated with salt and very dry appeared to make grading and measurement more difficult. However to clarify this and to

ensure that any new methods were acceptable to the purchaser, various preservation treatments, packing methods and presentations were tested. The quality of the leather produced, and the views and reactions to the treatments were obtained from the purchaser during the visit to Japan noted above.

3.3 Experimental

3.3.1 Short-Term Preservation

The temperature of a crocodile skin was logged from the time of slaughter through to the point of long-term preservation to identify periods of time when the skins were most susceptible to degradation from heat or microbes. Short-term storage conditions were surveyed and the cause of various skin stains and skin damage determined. The use of sodium chlorite as a preservative was investigated after indications that it caused damage. Samples of fresh skin were tested with the sodium chlorite treatment and compared with freezing and wet salting.

An alternative short-term preservation process, using brine solution was tested as a replacement for sodium chlorite. Raw skins were placed directly into solutions of salt (approximately 4 litres of liquor for a 2 kg skin) that were either 100% saturated or 60% saturated (containing approximately 220 g / litre of salt, without additives, in water) for 24 hours, with hourly stirring for the first 4 hours.

3.3.2 Long-Term Preservation – Interim Process

The interim recommended long-term preservation entails application of 500 g of ‘hide salt’ for a 40 cm skin (pro rata for larger or smaller skins) spread only on the flesh side with particular attention to the legs and edges. The skins are then stacked grain side down with the backbone along the ridge of a shallow inverted-V tray to drain for 24 to 48 hours. A small amount of salt is spread beneath the bottom-most skin, the stack of up to 15 skins covered with a polythene sheet to prevent drying and placed in a cool area. After draining, the wet salt is removed with a stiff brush and the skins resalted using 500 g of salt per skin. They can be restacked for several days to stabilise or rolled or folded for storage, ensuring that the salt remains with the skins. The skins should not be rolled or folded in a way that enables drained liquid to accumulate in skin folds. ‘Hide salt’ comprises fine, refined and kiln dried salt containing 1.25% each of sodium fluoride and boric acid and is commercially available.

3.3.3 Long-Term Preservation Process Development

3.3.3.1 Trial 1 Laboratory Scale Experiment (Crocodile Pieces)

Materials and Methods Two fresh crocodile skins were cut into pieces of approximate size 14 x 9 cm (i.e. approximately 38 pieces per 45 cm skin). The pieces were allocated to a chemical treatment type so that each treatment had a total of 4 pieces to investigate 4 storage options using standard vacuum storage bags. For each treatment, one piece was either sealed in a bag with vacuum, sealed with no vacuum, place in a bag that was folded closed but not sealed, or placed in a bag that was left open. The samples in the open bags were inoculated each time they were assessed with a fungal spore mix including 12 species cultured at CTFT and spores that were cultured from the Koorana crocodile farm. This method of testing the preservation was denoted as the ‘Re-exposure test’.

A small strip (1.2x3 cm) from each of the treatments was also used for the standard fungal ‘Challenge test’. The Challenge test entails placing the skin flesh-side down on an agar plate and inoculating the agar around the skin with the spore mix. The agar supports fungal growth and hence a continuous challenge to the skin piece. Failure of the preservative is shown by fungal hyphae and spores growing onto and in the skin piece.

To represent the effect of the short-term preservation, all crocodile skin pieces were pre-treated by soaking in excess saturated brine solution over night (20hrs) prior to final treatment. The skins pieces were then drained, weighed and transferred to a 500 ml bowl with a 200% ‘float’ of saturated brine

(200% liquid v/w based on the weight of the skin piece) containing the additives that were assigned for each of the solution treatments, also based on skin weight. After standing for 20 h with occasional stirring during the first 4 hours of treatment, pieces were drained on an inclined rack for 4 hours prior to packing. Solid treatments were purged overnight on an inclined rack. The treated crocodile skin pieces were folded flesh-side in and placed in bags as noted and incubated at 30oC for three to four months. The treatments are detailed and information on the various biocides provided in the Section 3.4.3.1. It should be noted that the selection of biocides tested is drawn from a range of current commercially available products and is not intended to limit or endorse the representation of any one in preference to another. Other suitable products are available and indeed, diversification is essential to control development of biocide resistant organisms.

Assessment Regime Assessment of the sealed- or closed-bag samples only occurred at the end of three months when all samples were opened and either passed or failed. Assessments of the Re-exposure test (which were re-inoculated on each occasion) and Challenge test samples were performed fortnightly up until 8 weeks, then monthly for the last 2 examinations. Scale slip was assessed on a scale 0 to 10, with 0 representing no scale-loosening and 10 representing complete loosening (light scraping of side of finger to completely remove scale). A rating of 2 or more is considered to be unsatisfactory for preservation purposes. Odour was assessed by any distinguishable odour other than from the fresh skin or preservative, on a 0 to 10 scale (0 no detectable odour and 10 putrid odour). A rating of 2 or more would indicate failure of the preservative. Pieces were removed from the trial at the point of failure.

3.3.3.2 Trial 2 Industry Scale Experiment (21 Crocodile Skins)

Materials and Methods Twenty one fresh, unfleshed crocodile skins were separated into 3 groups so that each treatment contained 7 skins. All skins were pre-treated by soaking overnight in cold 60% brine (4 l / skin for approximately 2 kg skins) then treated as followed:

Treatment A – Skins were removed from the 60% brine, drained 1 hour and then salted for 24 hours with excess solid ‘hide salt’ containing 1.25% w/w each of sodium fluoride and boric acid. Next day, the skins were hanged on a line for 1 hour to remove excess purge liquor, the excess salt brushed off, and vacuum packed (note that this is a modified version of the interim recommended procedure and used as a control for the other treatments)

Treatment B – The skins were removed from the brine, to which Preventol WB (0.5% based on skin weight) was added followed by more salt (without additives) until fully saturated. The skins were returned to the liquor and soaked overnight. Next day the skins were hanged on a line for 1 hour to drain and vacuum packed.

Treatment C – The skins were removed from the brine, Preventol WB (0.75%) was added to the 60% brine and dispersed and the skins returned and stirred thoroughly. Next day the skins were hanged on a line for 1 hour to drain and vacuum packed.

The width of each skin was measured at each step of the processing, i.e. raw, after 60% brining, and after treatment final immediately prior to packing. The width measurement was made at the third scute below the front legs.

Assessment Regime Assessment of the acceptability of the preservation was made by the overseas processor.

3.3.4 Storage, Packing and Presentation Experiment (25 Crocodile Skins)

The effect of packing (vacuum or non vacuum), folding style (conventional or ‘open’) and period in storage (several weeks or 6 months) on the appearance of the skins, ease of width measurement and grading upon receipt by the processor were studied. In addition, acceptability of brining as a preservation method from the perspective of appearance and behaviour rather than as a means of preventing microbial degradation was also tested (Table 1).

One group of skins was folded conventionally with the legs, head and flanks folded into the middle and the skin folded from head to tail in three or four folds with one fold falling just above the line of measurement at the shoulder. The alternative to conventional folding used the same pattern but with the flanks left outward, termed “open-folded”. This maintained the skin in a flat state across the line of measurement. Conventionally or open-folded skins were then either vacuum packed or sealed in bags without vacuum.

Treatment Preservation Methods Folding and Packing 5 skins/group (all skins initially 60 % brined o/n) A Drained then salted with excess solid hide salt Conventional folding method for 2 days. Loose salt brushed off and skin and packed in sealed bag with measured and packed no vacuum B After 60% brining, placed in 100% brine with Open folding method and excess salt for 2 days. Drained 1 hour, packed in sealed bag with high measured and packed vacuum C After 60% brining, placed in 100% brine with Open folding method and excess salt for 2 days. Drained 1 hour, packed in sealed bag with no measured and packed vacuum D Drained then salted with excess solid hide salt Conventional folding method for 2 days. Loose salt brushed off and the skin and packed in sealed bag with measured and packed, stored 6 months no vacuum E Drained then salted with excess solid hide salt Conventional folding method for 2 days. Loose salt brushed off and skin and packed in sealed bag with measured and packed, stored 6 months high vacuum Table 1. Treatments for storage, packing and presentation studies on 25 whole crocodile skins.

Five skins were used for each treatment and all skins from each treatment were pre-treated by soaking overnight in cold 60% brine (4 l / skin for approximately 40 cm skins). The skins were shipped to a Japanese processor and opened in the presence of the researcher. The comments of the processor were recorded and the skins measured and photographed.

3.4 Results and Discussion

3.4.1 Short-Term Preservation

The ambient and surface temperature of a typical skin was measured from immediately after slaughter and disinfection through to skinning. Temperatures were logged near the tail, on the belly and on the rear axilla (‘armpit’) where the leg hangs against the carcase (Fig. 4).

Temperature of Skin After Slaughter and Disinfection

C 25 o Axilla Skinning 20

15 Belly

Temperature Temperature 10 Control Cool room anomaly 5 near tail 0 12:00 15:00 18:00 21:00 0:00 3:00 6:00 9:00 12:00 Time (Start 15:21)

Figure 4. Temperature log of skin surface and ambient temperature from disinfection to skinning

The result illustrates (Fig. 4) that in a cold room at 4oC, it requires about 4 hours for the skin surface to fall to below 10oC; and that the axilla lags approximately 4 hours behind the temperature of the exposed skin area. The relatively slow rate of skin cooling, caused by the necessity to cool the entire carcase before skinning, would contribute significantly to the risk to skins from bacterial and enzymatic damage. This is particularly so in the axillae and where carcases are in contact, because of the lag in cooling. Poor preservation would show up first in theses areas. By comparison, the sheep and cattle industries remove the skins from carcases immediately after slaughter and aim to preserve or process them as soon as possible, often within minutes, after removal.

After skinning, the crocodile skin temperature was recorded through to initial preservation and fleshing (Fig. 5). As the skin is removed from the carcase, it quickly rises above the abattoir temperature to around 17oC because of the handling and its low mass and large surface area. Due to the imperative of processing the meat according to food standard requirements, further processing of the skin may be delayed until time is available to continue.

In order to minimise risk to skins at the pre-skinning stage, carcases should be chilled as quickly and uniformly as possible. The disinfectant swabbing, specified for food hygiene, is also a useful first skin-preservation step. It could be optimised by ensuring that it is thorough, particularly around the axillae, cloaca and slaughter incision, and perhaps with a higher than minimum concentration of disinfectant and a cold spray or dip. The chiller should be of high cooling capacity and the carcases well separated.

Temperature of Skin from Removal to Preservation

35 Skin moved to proecessing area for C

o 30 measurement, fleshing, trimming and Skin moved to 25 long term preservation Skinning processing 20 area coldroom Skin treated in cold 15 room overnight with sodium chlorite 10 Holding

Skin Temperature Temperature Skin solution time in 5 skinning 0 9:00 15:00 21:00 3:00 9:00 15:00 Time (Skinning Start 09:00)

Figure 5. Temperature log of skin from removal to preservation

As soon as removed from the carcase, skins should be placed in a short term preservative solution rather than left piled up and uncovered. In addition to exposure to microbial attack, areas of the skin can be subject to drying which will make both preservation and subsequent processing uneven.

At the time of study, fresh skins were treated overnight in a cold solution of sodium chlorite, a preservative commonly used in the cattle hide industry. They were fleshed, trimmed and measured and put into long term preservation over the following several days. However it was observed that the chlorite treatment caused dulling and erosion of the scale surface and hence considered to be at risk of causing other damage. A review of skins that had been processed and stored some weeks earlier revealed similar erosion and also significant scale slip. Skins also appeared to be excessively soft beneath the scales.

Samples of fresh skin were tested with the sodium chlorite treatment and compared with freezing and wet salting and it was conclusively demonstrated that the chlorite was responsible for the scale slip and erosion. The grain surface under the scale appeared excessively soft and spongy although no further analysis was conducted as the erosion and slip meant that the treatment was unacceptable. The sensitivity of crocodile skins to chlorite was unexpected and the underlying cause remains to be determined.

The first alternative tested was immediate transfer of skins to cold saturated brine solution. Initial results demonstrated that saturated brine removed (purged) water from the skin too rapidly and completely, resulting in “salt-burn” or excessive dehydration that appears as thin translucent areas (Fig. 6), and is difficult or impossible to reverse. Therefore, it was recommended that skins be placed in cold 60% brine (i.e. water containing sodium chloride to the extent of 60% saturation, or approximately 150 g / l) for up to 2 days for short term preservation of up to 5 days. As an alternative to chlorite, cold saturated brine was suggested.

Figure 6. Translucent areas on raw skin due to excessive and rapid dehydration in 100% brine.

3.4.2 Long-Term Preservation – Interim Process

In order to immediately eliminate bacterial and fungal damage from skins, an interim preservation process was implemented, based on practices elsewhere in the hide and skin industry.

The interim recommendation was that standard ‘hide salt’ be used for long-term preservation of the short-term preserved skins, instead of salt without additives. Hide salt is routinely used by the hide and skin processing industry. It is supplied ready mixed by salt manufacturers and comprises fine, refined and kiln dried salt containing 1.25% each of sodium fluoride and boric acid.

Any salting process results in the loss or purging of substantial amounts of water from the skin through osmosis. The conventional method of salting and folding or rolling allowed this water to accumulate in the lowermost folds and both waste large amounts of salt and cause unevenness in the skins. Therefore it was strongly recommended that a shallow inverted-V tray be used with the skins placed grain (scale) side down along the ridge. Skins should be covered and placed in a cool dark area to prevent drying. This allows the skins to drain rapidly and uniformly. The uniformity of the treatment and the efficiency of salt use are improved by using two small applications rather than one large one.

3.4.3 Long-Term Preservation Process Development

Although the interim process discussed above is highly reliable, it was not perfectly suited to crocodile skins because of their particular requirements for grading, measurement and packing. Therefore a preservation process more appropriate to crocodile skins was developed. Brining was selected as the basis of the process because application of a solution has some intrinsic advantages over application of a solid, and because salt is a non-toxic, inexpensive and effective biostat or biocide for most organisms and requires relatively little augmentation to make it highly reliable. Sodium fluoride and boric acid work well with solid salt so they and a number of other potential biocide treatments were assessed and the active ingredients are tabulated (Table 2). There are a number of strict regulations associated with all of these chemicals and none should be used without first verifying their occupational health, safety and environmental suitability.

Preservative Active ingredients Preventol WB sodium p-chloro-m-cresol + sodium o-phenylphenate Preventol CTL sodium p-chloro-m-cresol + 2-n-octylisothiazolin-3-one DCM dimethyl dithiocarbamate TCMTB 30% 2-(thiocyanomethylthio) benzothiazole BAC benzalkonium chloride Bronopol 2-bromo-2-nitro-1,3-propanediol Table 2. Active ingredients of preservatives tested

Brining as a preservation option was tested as part of the storage and packing trial (see Sections 3.3.4, 3.4.4) to ensure that it would be acceptable, in principle, to the processors from the viewpoint of presentation and handling. The results of this trial, involving 10 brined skins and 15 salted controls, were very positive with the skins being well received and in good condition. Skins were brined immediately before shipment to Japan, and opened in the presence of the researcher four weeks later so long-term preservation was not required or assessed.

Preservation treatments were tested for biostatic or biocidal efficacy by assessing the appearance, smell and scale looseness subjectively. In addition, pieces were subjected to repeated (‘Re-exposure test’) or continuous (‘Challenge test’) exposure to a mixture of fungal spores including twelve standard varieties maintained at CSIRO TFT and others cultured from those isolated from Koorana Crocodile Farm. These are industry standard tests for the efficacy of fungicides (which also can act as potent bactericides). Skins were incubated at 100% humidity and 30oC to simulate the most extreme anticipated storage conditions.

The ‘Re-exposure test’ is used as a simple general indicator of the susceptibility of the skins to microbial attack. The Challenge test, which simulates the continuous exposure experienced in the natural environment and the presence of alternative nutrients, is more stringent in indicating whether preservatives are persistent or fugitive, and whether they suppress both growth and germination of fungal spores. Passing the Challenge test, entailing prevention of microbial, primarily fungal, growth for at least 4 weeks and no evidence of odour, damage or scale slip, (normally indicative of bacterial activity), is used as a highly reliable criterion for an effective biocide. Due to the particularly severe environment in which crocodile skins are produced, and the long delays between production and processing to leather, preservatives with better results for the Challenge test than 4 weeks were preferred.

3.4.3.1 Trial 1 Laboratory Scale Experiment (Crocodile Pieces)

Industry-standard formulations (Table 3) of commonly available biocides were assessed as to their effectiveness for preserving crocodile skin pieces. The pieces that had been stored in sealed or closed bags were all found to pass at three months, with no evidence of bacterial or fungal deterioration, scale slip or odour (Table. 3). This indicates that all of the treatments either sterilised the skins or reduced the microbial activity to such a low level that it had not recovered significantly in three months. The vacuum storage bags, whether sealed or closed, may be an effective means of preventing re-contamination or, perhaps, loss of the biocide from the skin,

The ‘Re-exposure test’, entailing regular inoculation of the samples, indicated that all of the treatments exhibited good fungicidal as well as bactericidal properties as indicated by the absence of scale slip or odour for failed treatments (3, 7, 10, 12, 19). As expected, saturated brine alone (treatment 19) fails relatively quickly (6 weeks) as a fungicide.

The Challenge test caused all treatments other than Preventol WB and Preventol CTL at 0.5% to fail. Even solid salt, with additives, fails after 10 weeks illustrating the need for an appropriately selected and applied treatment. Initial trials (not reported here) were carried out using fresh cattle hide pieces and shorn sheepskin pieces to assess reliability and suitability of various long-term alternatives in combination with the short-term preservation options and industry requirements, before proceeding to crocodile skins.

‘Re-exposure test’ open bag, regular Challeng Test Preservation method inoculation e test no. (all pieces initially treated Weeks of Scale-slip Odour at Weeks of overnight with saturated brine) protection end 3 m end 3 mo protection 1 0.2% Preventol WB >17 0 0 7 2 0.5% “ “ >17 0 0 >17 3 0.2% DCM 6 0 0 5 4 0.5% “ “ >17 0 0 7 5 0.2% Preventol CTL >17 0 0 10 6 0.5% “ “ >17 0 0 >17 7 0.2% TCMTB 6 0 0 7 8 0.5% “ >17 0 0 10 9 0.5% BAC >17 0 0 7 10 0.5% ZnCl2 8 0 0 <1 11 0.2% Preventol WB o/n then >17 0 0 10 lightly salt next day 12 0.2% Bronopol 6 0 0 <1 13 0.5% “ >17 0 0 <1 14 0.5% NaF >17 0 0 <1 15 1% “ >17 0 0 <1 16 0.25% each of NaF + H3BO3 >17 0 0 <1 17 0.5% each of NaF + H3BO3 >17 0 0 <1 18 Salt containing 1.25% each of NaF >17 0 0 10 + H3BO3 19 Sat’d brine only 6 0 0 <1 Table 3. Results for treatment of crocodile skin pieces with various preservatives and re-exposure or continuous challenge with fungal attack.

3.4.3.2 Trial 2 Industry Scale Experiment (21 Crocodile Skins)

Following the results of Trial 1, the preservative Preventol WB (PWB) was selected for further study and to gauge industry response to a new process. The trial involved comparison of conventional salting and treatment with saturated brine solution containing the biocide at 0.5% w/w and is summarised (Table 4). At the time of this trial, it had become apparent that solid salt and saturated brine could be responsible for significant shrinkage, so the trial included 60% brine with PWB at 0.75% w/w in 200% float (w/w of skin). The higher dosage was used to ensure reliability in the more dilute brine as no data were available up to this point.

Use of brine as a basis for preservation was considered important because of its ready acceptability in industry. Suggested short and long term preservation procedures are provided in Appendices 1 and 2 respectively. Dispensing with salt entirely would entail a much larger research and development effort than could be accommodated in the present project.

Treatment Initial Final preservation Vacuum Storage 7 skins/group preservation packing A 60% Brine o/n Solid salt Yes 1 month B 60% Brine o/n Sat. brine+0.5% PWB Yes 1 month C 60% Brine o/n 60% Brine+0.75% PWB Yes 1 month Table 4. Summary of treatments applied to 21 skins

Skins were treated and packed in individual bags with vacuum and exported. Commercial constraints resulted in the skins being sent to a European processor rather than to the Japanese tanner and it did not prove possible to acquire first-hand assessment of the material or access to the finished leather. However, the skins were received and paid for without demur or subsequent complaint from the processor so it can be inferred that the treatments used to preserve them were all adequate. The vacuum packing was at the discretion of the producer and did not influence the outcome of the trial as demonstrated elsewhere.

Following the successful trialling of 60% saturated brine with 0.75% Preventol WB, this treatment should be considered for long term preservation treatment for crocodile skins. Further testing should be conducted to verify these results prior to full implementation, particularly where conditions vary from those described. The level of Preventol WB is possibly higher than necessary but can be fine- tuned as experience is accumulated. It should be emphasised that Preventol WB is used as an example of an effective biocide and is not exclusively or specifically recommended for this purpose. Many other products are available, and indeed, it is very important that satisfactory alternatives be identified as some products are occasionally changed or removed from the market and it is critical to have a readily available alternative to avoid disruption to processing or sales.

3.4.4 Storage, Packing and Presentation Experiment (25 Crocodile Skins)

The effect of packing, folding, period in storage and preservation method on the appearance of the skins, ease of width measurement and grading upon receipt by the processor were studied (Table 5).

As noted above (Section 3.4.3.2) brining was found to be a feasible preservation and presentation option from the perspective of appearance and behaviour so trials to develop brining as a reliable preservation method were commenced. The brined skins carried some liquid in the bags but although this was unfamiliar to the processor, it was not seen as a problem. The salted skins, particularly those that had been in storage for 6 months, were relatively difficult to unfold and flatten, and the dry salt crust made observation of the grain surface more difficult.

Folding with the flanks out (open folding) eliminated the creases across the line of measurement and allowed skins to lie flat. Unfolding was more difficult for skins that had been salted, and particularly for skins that had also been vacuum packed or stored for an extended period. Open folding was well received and appears to be acceptable to the processor. The sample size was too small to be certain as to whether the method increases the width of the skins as measured by the processor, however it clearly allows the skins to lie flat and be spread more easily. Further analysis of the results of width measurements under various conditions is given in Section 4.

Packing skins in sealed plastic bags is beneficial in keeping them clean, preventing re-contamination with micro-organisms, maintaining a stable environment of moisture and preservative and simplifying shipping and handling. If packed with the CITES numbers and prime area (belly) visible, the skins can also be sorted, tracked and even, to some degree, graded. Many other products of much lower value are packed as well or better than this for similar reasons.

Tr’m’t Treatment Assessment of Assessment of Assessment of 5 skins / summary preservation folding, effect on packing group measurement A Solid salt, Well preserved, Creases across Skins dry, flatten no vac, dry measurement line reasonably easily normal fold B Sat. brine, Well preserved, No creases across Skin scales indented vacuum, some free liquid measurement line, from pressure, folds open fold present (not spreads easily for slightly resist flattening detrimental) measurement C Sat brine, Well preserved, No creases across Skin soft, spreads no vacuum, some free liquid measurement line, easily and lies flat open fold present (not skin spreads easily detrimental) D Solid salt, Well preserved, Creases across Skins dry and difficult no vac, 6 dry and stiff measurement line to flatten or measure mo hard to flatten normal fold E Solid salt, Well preserved, Creases across Several bags punctured vac, 6 mo very dry and stiff. measurement line by salt. Some scales normal fold very hard to indented by pressure. flatten Skins dry and hard to flatten or measure. Table 5. Effect of folding, packing and storage time on presentation and measurement

3.5 Conclusions and Recommendations

Skins are at least as putrescible as meat and very much more valuable so should be afforded the same high priority in preservation. This should commence from the moment an animal is slaughtered and continue unbroken through to final leather processing. Key factors are to correctly apply appropriate preservatives at the earliest possible time, avoid delay and avoid any exposure to unnecessarily high temperatures.

Initial processing could include effective disinfection and rapid chilling of the skin on the carcase, followed by immediate transfer to a short term preservative after skinning. The preservative recommended is cold 60% brine solution made with clean salt (220 g in one litre of water) without additives (refer to Appendices 1 and 2 for detailed processes). The skins should be left in for at least 24 hours for preservation for up to 5 days. Note that skins can progress to final preservation at any time.

Long term preservation should seek to ensure that the skins remain undamaged and in an attractive state for the anticipated period and conditions of storage and shipment, including an appropriate safety margin. The suggested procedure is to soak the skins in 60% brine solution containing an appropriate preservative. The product Preventol WB was tested and found to suitable at the level of 0.75% w / w on the skin weight. A lower level may be suitable and can be tested once the process is established. Preventol WB is given as an example only and not specifically endorsed or recommended. Many other commercial biocides are available and indeed it is very strongly recommended that alternatives be found and tested to ensure adequate control of organisms and flexibility of operation. Salt alone, whether dry or as brine, is not an adequate preservative.

Disposal of any chemical can cause harm to the environment, and care must be exercised in ensuring that appropriate precautions and procedures are followed. Local regulations and company literature relating to all chemicals used should be consulted to identify limits and treatments applicable.

Folding such that the line across the skin at the third scute used for measurement remains un-creased is recommended as such skins present well and are easy to spread out and measure. There may be a small benefit in increased width as measured after unpacking, although this would require careful study to prove.

Individual packing in sealed bags, particularly if the CITES number and the main panel area are visible, is highly recommended as it keeps the skins in excellent condition and simplifies handling. Use of vacuum is not recommended as it causes more severe creasing and scale indentation, cannot be guaranteed to persist because of leaks and punctures, and is of no clear benefit for preservation. Short and long term preservation procedures are given in appendix 1.

The pressure applied to the skins by vacuum packing is seen to cause indentation of the scale surfaces and to make the creases harder to straighten out. Although these effects do not appear to persist into the finished leather, they make measurement and grading slightly more difficult and are thus a minor detriment. Unreliability of the vacuum, caused by difficulties in sealing the bags, or subsequent puncturing by salt crystals or other sharp particles or objects (grit, scales etc), would require that an alternative preservation system be present. Thus there does not appear to be any significant benefit from use of vacuum and it cannot therefore be recommended.

4. Shrinkage

4.1 Background and Objectives

The accepted practice in skinning crocodiles for leather products is to open the skin along the back and remove a “back strap’ from the carcase that is 4 scutes (raised bony scales) wide. The remaining scutes form the edges (flanks) of the skin when removed, with the belly at the centre. The normal method of valuing crocodile skins, after grading, is by their width as measured at the third raised scute, approximately 8 cm below the “shoulder” for a 40 cm wide skin (Fig. 7). This measurement usually occurs at the producer and again on receipt at the processor with the latter taking precedence. The price is set as a value per centimetre, usually around US$9, or US$360 for a 40 cm wide skin.

Figure 7. Measurement of crocodile skin at 3rd scute below ‘shoulder’

During the course of research into preservation and packing, it became apparent that the crocodile skins underwent contractions in width from the time of preservation through to the beginning of processing into leather to the extent of about 10% with a very high variability. In cattle hide and sheep skin processing, this variation is less critical. Any change in width (or area) that occurs from abattoir to processor is dealt with by the latter with the assumption being that any loss is regained during processing. As crocodile skins are measured and valued at an intermediate stage, the exact timing and extent of shrinkage could affect the return to the extent of up to about 10%.

The regain in width from the preserved skin to the finished leather was thought likely to have been factored in to the prices offered by processors. Therefore, any overt or contrived attempt to increase the width of the skins by, for example, stretching them while they are being salted or dried, would result in the price being offered being reduced and entail significant effort on the part of the producer for no net return. Moreover, any increase in width must be stable and not disappear over time, nor should any methods used interfere with subsequent processing, e.g. by over-drying or tearing skin fibres.

Some reduction in width appears inevitable, particularly from the fresh state to initial preservation as the skin plasma is removed and soluble protein coagulated. However, it appeared feasible to stabilise the width of the skins at a point significantly above their minimum without disrupting the pricing

mechanism and thereby losing any benefit. The objective was set to achieve a 5 percentage point average increase in width accepted by the processor and with no negative pricing signals.

4.2 Methodology

The points within the process where shrinkage occurs were initially identified by using fresh cattle hide as a model, followed by crocodile skin pieces and then whole skins. For practical purposes, area change was used in lieu of width for experiments involving small skin or hide pieces. Studies that utilised whole crocodile skins examined width variation directly by measurement at the standard 3rd scute position. Finished leather is trimmed to remove these scutes (roughly 2 cm on each side for a 40cm skin) so width is not directly comparable to that of raw skins, however it is systematically related and will be used without adjustment or interpretation.

The key variable was identified as being salt exposure, specifically mode (solid or solution), amount and timing. Although this overlaps with preservation studies, the issues are presented separately for clarity.

4.3 Experimental

4.3.1 Trial 1 Hide Piece Area Loss

Hides used for this experiment were collected fresh from the abattoir and frozen, then thawed when needed. They were cut into pieces of approximate size 14 x 9cm and allocated such that treatments A & B each had a total of 24 pieces, and C used 26 pieces. All pieces were pre-treated overnight with 60% brine and then fully preserved with either salt, 100% brine or 60% brine and 0.5% PWB (Table 6).

Treatment Initial Final preservation Vacuum Storage pieces/group preservation packing A (24) 60% Brine o/n Drain 4 h, solid salt Yes, 12 3 months B (24) 60% Brine o/n Drain 4 h, sat. brine Yes, 12 3 months C (26) 60% Brine o/n Drain 4 h, 60% Yes, 12 3 months brine+0.5% PWB Table 6. Summary of treatments applied to hide pieces

After treatment, all the hide pieces were drained for four hours before bagging. Twelve pieces from each treatment were vacuum packed and the rest were packed in zip-lock bags. All pieces were incubated at 30oC.

The area of every sample was measured before and after final preservation, at the end of 3 months storage and after soaking back (re-hydrating by tumbling in fresh water for 24 hours). As skin and hide pieces do not maintain a symmetric or regular shape after cutting, they were digitally scanned and the areas measured by image analysis using PhotoImpact software. Pieces were spread out evenly and a plate placed on top to maintain uniform flatness and pressure.

4.3.2 Trial 2 Crocodile Skin Piece Area Loss

One fresh raw crocodile skin was divided into twenty nine pieces (Fig. 8) and sorted into three groups of seven and one of eight to achieve a uniform distribution of treatments A to D (Table 7).

Treatment Initial Final preservation Vacuum Storage pieces/group preservation packing A (7) 60% Brine o/n Drain 4 h, apply excess No 3 months solid salt B (8) 60% Brine o/n Transfer to 100% brine + No 3 months 0.5% PWB for 1 day C (7) 60% Brine o/n Transfer to 60% brine + No 3 months 0.75% PWB for 1 day D(7) None Soak in 60% brine and No 3 Months 0.75% PWB 2 days Table 7. Summary of treatments applied to crocodile pieces

After treatment, all the crocodile pieces were drained for four hours before packing individually in zip-lock bags and incubation at 30oC. The area of every sample was measured as for the hide pieces (Section 4.3.1). Note that treatment D did not include pre-treatment with 60% brine, and pieces were not vacuum packed.

Figure 8. Division of crocodile skin for Trial 2

4.3.3 Trial 3 Whole Skin Width Loss (25 Crocodile Skins)

Treatments applied to the twenty five skins used for the packing and storage experiment (Section 3.3.4) are summarised (Table 8). The skins were measured immediately after final preservation, on receipt by the processor (i.e. after storage) and as finished leather. Skins in groups A, B and C were also measured in the fresh raw state before preservation.

Treatment Initial Final preservation Folding Vacuum Storage 5 skins/group preservation packing A 60% Brine o/n Excess solid salt Normal No 1 month B 60% Brine o/n 100% Brine, 2 days Open Yes 1 month C 60% Brine o/n 100% Brine, 2 days Open No 1 month D 60% Brine o/n Excess solid salt Normal No 6 months E 60% Brine o/n Excess solid salt Normal Yes 6 months Table 8. Summary of treatments for storage, packing and presentation studies on 25 whole crocodile skins.

4.3.4 Trial 4 Whole Skin Width Loss (21 Crocodile Skins)

Treatments applied to the twenty one skins used for preservation studies (Sections 3.3.3.2, 3.4.3.2) are summarised (Table 4, reproduced below for clarity). All skins were measured in the raw state, and following initial and final preservation. Data could not be acquired after storage and processing.

4.4 Results and Discussion

4.4.1 Trial 1 Hide Piece Area Loss

A preservation and shrinkage trial (Section 4.3.1, Table 6) was conducted using 74 cattle hide pieces as a model for crocodile skins in order to identify key issues for further study. The areas of the hide pieces (pre-treated with 60% brine and then with either solid salt (Group A), 100% brine (Group B) or 60% brine (Group C) showed changes of -24.0%, -26.3% and -14.6% respectively (Fig. 9, column 1) immediately after preservation. Over a three month period, the areas rebounded by 3 to 4 % (col. 2) whilst all area loss was recovered when the hide pieces were soaked back (col. 3).

5% 0% -5% -10% C -15% -20% -25% A

% Change in width % Change B -30% 123

A -24.0% -21.2% 1.5% B -26.3% -22.4% 0.6% C -14.6% -10.2% 2.2%

Figure 9. Cumulative Area change of hide pieces subject to preservation (Column 1: Raw to Preserved, 2: Raw to End of Storage (3 mo.) 3: Raw to Soaked Back

The percentage changes for each step illustrate (Fig. 10) the rebound more clearly, and the recovery of area on soaking. If hides were measured and valued in the preserved state (col. 2) producers would experience the major loss of area (col. 1) whilst processors would benefit from the major gain in area (col. 3). Both salting (A) and 100% brining (B) experienced variations of around +/-25% whereas 60% brining was limited to about +/- 15%

30%

20%

10%

0% ABC -10%

-20% % Change in width % Change -30% 123

A -24.0% 3.7% 25.1% B -26.3% 5.5% 28.9% C -14.6% 5.7% 9.4%

Figure 10. Stagewise area change of hide pieces subject to preservation (Column 1: Raw to Preserved, 2: Preserved to End of Storage (3 mo.) 3: End of Storage to Soaked Back

Half of the hide pieces used in this trial were vacuum packed for three months to determine if there was any effect on area. However the results for the vacuum packed and conventionally packed skins were indistinguishable, indicating no effect due to vacuum packing.

4.4.2 Trial 2 Crocodile Skin Piece Area Loss

Following the results of the major trial using hide pieces, a trial using crocodile skin pieces was conducted, to test both area loss and gain, and efficacy of preservation. Conditions were the same as for the previous experiment, comprising salting (Treatment A), and brining (B -100%, C - 60%) although vacuum packing was not included. A fourth treatment (D - 60% brine with Preventol WB (0.75 %) combined for two days), comprising a modified version of treatment C (60% brining for one day, then soaking in 60% brine combined with Preventol WB (0.75%) for one day) was included. Pieces were incubated at 30oC for three months to test preservation and simulate harsh storage conditions.

-5% D

-10% ABC % Change in width -15% 123

A -10.9% -10.8% -8.4% B -8.5% -9.1% -7.6% C -10.7% -12.4% -8.9% D -5.2% -7.7% -6.4%

Figure 11. Cumulative area change of crocodile skin pieces subject to preservation (Column 1: Raw to Preserved, 2: Raw to End of Storage (3 mo.) 3: Raw to Soaked Back

All pieces shrank by an average of around 8.8% immediately (Fig. 11 col. 1) and continued to contract slightly over time to an average of about 10% loss (col. 2) but soaking back only recovered a

small proportion of the area, back to about 7.8% loss (col.3). The variation in the area loss did not appear consistent or in accord with the results seen for hide pieces. Treatments C and D were virtually identical, with only the timing of the Preventol WB application being adjusted for preservation purposes. However the shrinkage for these two treatments was at opposite extremes of the range observed. Failure of the skins to recover their area on soaking back was uniform across the treatments, but unexpected.

The area changes for each step illustrate more clearly (Fig. 12) that following the initial contraction (col. 1) the area continues to decline slightly over time (col. 2), with very little recovery on soaking back (col. 3). The mechanism of soak back entails gentle tumbling of skins in fresh water. The repeated flexing experienced by hides and skins is instrumental in separating adherent fibres and restoring the original area. The scales of crocodile skins may participate in the area loss to a greater extent than anticipated and then stop recovery by preventing much of the skin area from flexing.

-5% D -10% A B C % Change in width % Change -15% 123

A -10.9% 0.2% 2.6% B -8.50% -0.7% 1.9% C -10.7% -2.0% 4.1% D -5.2% -2.6% 1.5%

Figure 12. Stagewise area change of crocodile skin pieces subject to preservation (Column 1: Raw to Preserved, 2: Preserved to End of Storage (3 mo.) 3: End of Storage to Soaked Back

Treatment A Treatment B Treatment C Treatment D Piece no. Change% Piece no. Change% Piece no. Change% Piece no. Change% 1 -9.4 2 -6.3 3 -6.7 4 -9.6 5 -8.6 7 -17.9 6 -7.1 9 -1.5 12 -7.9 8 -3.1 10 -17.0 11 -3.1 16 -9.5 15 -9.5 13 -12.2 19 -4.9 17 -15.4 18 -3.9 14 -9.7 22 -9.2 20 -15.1 21 -13.8 23 -11.8 24 -4.9 25 -10.7 27 -6.1 26 -10.3 28 -3.5 29 -7.5 Mean -10.9 -8.5 -10.7 -5.2 Std Dev. 3.1 5.4 3.5 3.0 Table 9. Change in area from raw to end of preservation for individual crocodile skin pieces

Examination of the individual pieces in relation to their location on the skin and the treatment received revealed that the results had been confounded by the extreme variability of the skin at different points coupled with the sorting process aimed at creating balanced and comparable samples. The individual results (Table 9) indicate the range of values for each treatment. A map of the skin showing the treatments and area losses (from the raw to the preserved state) for the individual pieces illustrated (Figure 13) how the same treatment (letter) can cause drastically different shrinkage (number shown on piece) in different locations. The shrinkage is also colour coded and graphically

reveals that the two areas undergoing greatest shrinkage (pieces 7, 10) lie across the width measurement line. Another area of particular loss is that below the cloaca (20, 21).

Figure 13. Map of change in area from raw Figure 14. Map of change in area from raw to to end of preservation for individual crocodile end of preservation for individual crocodile skin skin pieces pieces after subtraction of group means and adjustment to previous minimum value (-1.5)

There are insufficient data to conduct anything but a rudimentary statistical analysis to gain a clearer impression of the effect of location or treatment. For example, subtraction of the mean area loss for a group of skins from the individual specimens in that group approximates to removing the effect of the treatment. The result, which is adjusted to have the same minimum loss (-1.5%) shows (Table 10, Fig. 14) considerably more consistency in most areas, particularly in the tail. The central area is more clearly defined as dimensionally stable whilst the upper flanks (7, 10) are very subject to shrinkage. The map also shows up pieces 4, 13 and 17 as being anomalous in having much higher loss (6.6, 4.5 and 4.5 percentage points greater respectively) of area than corresponding pieces elsewhere.

Treatment A Treatment B Treatment C Treatment D Piece no. Change% Piece no. Change% Piece no. Change% Piece no. Change% 1 -5.4 2 -4.7 3 -2.9 4 -11.3 5 -4.6 7 -16.3 6 -3.3 9 -3.2 12 -3.9 8 -1.5 10 -13.2 11 -4.8 16 -5.5 15 -7.9 13 -8.4 19 -6.6 17 -11.4 18 -2.3 14 -5.9 22 -10.9 20 -11.1 21 -12.2 23 -8.0 24 -6.6 25 -6.7 27 -4.5 26 -6.5 28 -5.2 29 -5.9 Table 10. Change in area from raw to end of preservation for individual crocodile skin pieces after subtraction of group means and adjustment to previous minimum value (-1.5%)

Further statistical analysis could include removal of the effect of location by subtracting the mean for ‘like’ pieces and renormalizing the data, however the limited data and presence of anomalous values make this of limited usefulness. Nevertheless from the wide variation in contiguous results it appears that the shrinkage is very susceptible to the exact sampling location. The rigidity, orientation and size of scales clearly influence the direction and extent of shrinkage, with much of the contraction occurring between the scales. The small rounded scales of the flank areas below the front legs, and to a lesser extent around the cloaca, would thus have the largest number of scale junctions and hence contract most severely compared with the large square scales of the belly. Of particular relevance is that this result illustrates the difficulty of using crocodile skin pieces for any developmental or testing purpose.

The difference in behaviour between hides and crocodile skins as illustrated by the failure of the latter to recover lost area on soaking back also demonstrates the necessity to work with crocodile skins rather than models. The variation is shown graphically by the digitised scans of a representative hide piece (Fig. 15) and crocodile skin piece (Fig. 16) at various stages of processing

Raw hide piece (No. Preserved After 3 m storage After soaking back 20, Treatment B) (-21.8%) (-18.2%) (+0.6%) Figure 15. Digital image of a hide piece at each stage of preservation from raw to soaked back, showing area change from raw state.

Crocodile skin piece Preserved After 3 m storage After soaking back (No 8, Treatment B) (-17.9%) (-20.6%) (-17.2%) Fig. 16. Digital image of a crocodile skin piece at each stage of preservation from raw to soaked back showing area change from raw state.

4.4.3 Trial 3 Whole Skin Width Loss (25 Crocodile Skins)

A trial was conducted utilising 25 whole crocodile skins separated into 5 groups (Section 3.3.4) with the primary objective of this study was to investigate packing and presentation (Section 3.4.4). The widths were measured in the raw state, immediately after preservation, after storage and after processing through to finished leather for all samples except D and E where data for the raw skins was not available. Although the leather is trimmed (by approximately 4 cm) and is thus not directly comparable to the raw skin width, it does nevertheless give a good indication. The treatments applied to the five groups are summarised (Table 11).

Treatment Preservation Vacuum Folding Storage packing A Solid salt No Normal 1 month B Saturated brine Yes Open 1 month C Saturated brine No Open 1 month D Solid salt No Normal 6 months E Solid salt Yes Normal 6 months Table 11. Summary of treatments applied to 25 crocodile skins

-2%

-4%

-6% A

-8% B C % change in width % change -10% 123

A -7.8% -6.0% -5.3% B -8.2% -7.1% -7.1% C -8.9% -7.0% -4.5%

Figure 17. Cumulative width change of 25 crocodile skins subject to preservation (Column 1: Raw to Preserved, 2: Raw to End of Storage (3 mo.) 3: Raw to Finished Leather (Groups A, B, C only)

The width from the raw state to the end of preservation was measured for treatment groups A to C and shows (Fig.17, col. 1) similar losses of 8 to 9% with 100% brining (B, C) being slightly worse than salting (A). This is reflected in the ‘salt burn’ phenomenon noted above, where saturated brine can cause excessively rapid and extreme dehydration of fresh skins. After storage for 1 month, the area rebounds slightly (col. 2) with losses down to 6 to 7%. Finished leather (col. 3) shows a small rebound also although the leather is trimmed and hence not directly comparable. The small rebound and recovery effect is illustrated more clearly by the stagewise changes in skin width (Fig. 18).

4% 2% 0% A B C -2% -4% -6%

% change in width % change -8% -10% 123

A -7.8% 1.9% 0.9% B -8.2% 1.2% 0.7% C -8.9% 2.1% 2.8%

Figure 18. Stagewise width change of 25 crocodile skins subject to preservation (Column 1: Raw to Preserved, 2: Preserved to End of Storage (3 mo.) 3: End of Storage to Finished Leather (Groups A, B, C only)

0% ABC -5% DE -10% % change in width in % change -15% 12

A 2% 3% B 1% 2% C 2% 5% D -12% -7% E -9% -6%

Figure 19. Cumulative width change of 25 crocodile skins subject to preservation (Column 1: Preserved to End of Storage (1 mo. for A, B, C, 6 mo. for D, E) 2: Preserved to Finished Leather)

Raw skin data for groups D and E were not available, hence cumulative change in area for the final two steps is shown (Fig. 19). After 4 weeks (col. 1, A,B,C) in storage, skins appear to rebound slightly in area from their area loss on preservation as noted above, whereas skins that have been stored for longer have undergone substantial further shrinkage (D,E). Over this period of time, the skins became very dry and hence it is likely that this caused the additional contraction. After processing to leather (col.2) there is some recovery in area for all groups. However for the skins that were stored for the extended period of time, this is not enough to make up for the loss during storage.

The loss of area on long-term storage and where the skins dries out is of particular relevance to the producer in that skins awaiting sale or in transit are potentially losing value. In addition, extended storage and drying appear to disadvantage the processor who is not able to recover the anticipated area. Leather made from such skins is likely to be thicker, stiffer and harder and hence of lower value.

No effect due to folding or vacuum could be discerned in the data, although the level of variation is such that a small effect cannot be ruled out. By far the overwhelming influence on area is the nature of the preservation (including salting and brining) and period in storage, including the loss of moisture over time (although drying was not considered as a viable preservation method). These data should be considered preliminary as a more fully developed and controlled trial is necessary to identify the precise causes and nature of area loss and regain.

4.4.4 Trial 4 Whole Skin Width Loss (21 Crocodile Skins)

The widths of 21 crocodile skins in three groups, processed as described above (Section 3.3.3.2), were measured at each stage of the procedure from raw; after initial preservation in 60% brine; and after final preservation with solid salt, 100% brine or 60% brine. The treatments are summarised again for clarity (Table 4, note that the brine contains Preventol WB):

Treatment Initial Final Vacuum Storage Preservation Preservation packing A 60% Brine o/n Solid salt Yes 1 month B 60% Brine o/n Saturated brine Yes 1 month C 60% Brine o/n 60% Brine Yes 1 month Table 4 ctd. Summary of treatments applied to 21 crocodile skins

-3% A B -6% C -9%

-12% Change in width (%) in width Change -15% 123 A -3.2% -12.5% -9.6% B -4.0% -13.3% -9.7% C -5.6% -7.6% -2.1%

Figure 20. Width change of 21 crocodile skins subject to preservation (Column 1: Raw to Initial Preservation (60% Brine), 2: Raw to Final Preservation (A Salt, B 100% Brine, C 60% Brine) 3: Initial Preservation to Final Preservation (A Salt, B 100% Brine, C 60% Brine))

After the initial 60% brine treatment (Fig. 20, col.1), the three groups shrank by between 3.2 and 5.6%, which, given that the groups and treatments are nominally identical, indicates the variability of the skins (Table 12). Final preservation using salting or 100% brine caused a further contraction to a total loss of 12.5% and 13.3% respectively, whilst loss due to 60% brining only increased to a total of 7.6% (Fig. 20 col. 2). Contraction due to the final stage alone (col. 3) illustrates most clearly that salt and 100% brine cause a contraction of almost 10% whereas 60% brine causes shrinkage of just 2.1%

Thus, use of 60% brine as the final preservative (including a biocide such as Preventol WB) reduces the loss in width compared with salting or 100% brine by almost 8% for the final preservation, or 5 to 6 percentage points overall.

Information on the width of the skins after storage and processing to leather, and on the quality and acceptability of the preservation processes could not be recovered. However all skins were received and paid for without demur or comment from which it may be inferred that all treatments were at least acceptable.

Treatment 7skins / Width measured at 3rd scute (cm) % Change in width group Raw to After init. After final Raw to init. final Init. to final Raw preserv’n preserv’n preserv’n preserv’n preserv’n A (Salt) 38 37 33.5 -3% -12% -9% 38 35.5 34 -7% -11% -4% 38 38 35 0% -8% -8% 39 38 34 -3% -13% -11% 48.5 47 41 -3% -15% -13% 49.5 47.5 42 -4% -15% -12% 43 41.5 37 -3% -14% -11% B (100% 38 35.5 32 -7% -16% -10% Brine) 43 41.5 36 -3% -16% -13% 43 42 37 -2% -14% -12% 47.5 45 43 -5% -9% -4% 44 44 40 0% -9% -9% 48 45 41 -6% -15% -9% 50 48 43 -4% -14% -10% C (60% 37 34 35 -8% -5% 3% Brine) 46 43.5 42 -5% -9% -3% 35 34.5 33 -1% -6% -4% 45 40 39 -11% -13% -3% 37 36 33 -3% -11% -8% 38 37.5 37 -1% -3% -1% 44 40 41 -9% -7% 3% Table 12. Individual widths and % change for 21 crocodile skins.

4.5 Conclusions and Recommendations

The issue of shrinkage arose during the course of the project and was found to be of considerable significance, resulting in an approximately 10% loss in width and hence value from the raw to the fully preserved state. The shrinkage is of particular relevance in crocodile skin trading because the skin is measured and valued at the preserved stage and the zone of greatest loss falls across the line of measurement.

The cause was identified as exposure to salt with solid salt and saturated brine being the most deleterious. Some shrinkage is probably unavoidable, however use of 60% brine with appropriate preservatives was found to limit this to about 5%. Use of brine, in conjunction with packing in individual bags, keeps the skin soft and easily spread, graded and measured on receipt. In addition, it may result in a higher yield of leather compared with skins that have been dry salted for an extended period of time although this would require further study to verify.

While the value of skins and hence return to the producer is assessed by width after preservation and storage, the producer should use methods which do not cause shrinkage. Thus 100 % saturated brine and solid salt should be avoided if possible. More stringent process control is necessary to use 60% saturated brine and it is recommended that a checking procedure (e.g. that the brine concentration is

checked prior to addition of skins and has a Salinometer reading of at least 60%) be included if this process is implemented. If space and facilities permit, preparation and storage of a large volume of 60% brine for use as required would reduce the need to test each batch. Recycling of exhausted brine liquor is possible provided appropriate precautions and controls are applied, but may only be feasible for large operations. Where the process control is lacking and the width loss is acceptable, the interim long term preservation method (described in Section 3.3.2) using solid commercial hide salt can be retained.

The variability of crocodile skins from animal to animal and from point to point within individual skins made the use of cattle hide or crocodile skin pieces as a model for process development of limited value. Use of whole skins is therefore necessary to ensure that results are reliable and reproducible. For relatively gross variables such as the shrinkage caused by salt, fewer than 10 skins per sample group will provide sufficient data to identify improvements. More subtle changes such as caused by folding would require many more skins. Whatever the issue however, it is essential that any alterations to process be based on sound experimental evidence.

5. Fault Identification

5.1 Background and Objectives

The blemishes on crocodile skins, particularly in the valuable main panel area of the belly, from collar to cloaca and flank to flank, are readily visible both in the live animal and post mortem. The various marks are used to estimate the value of the skin as finished leather and a grade given accordingly. For the live assessment, the option exists to slaughter the animal or retain it in order to allow blemishes (cuts, infections, scars, partial scales etc) to heal and fade, perhaps with intervention, depending upon the expected costs, risks and returns. Whether or not the animal is alive, the assessment allows the producer to identify causes of damage and hence loss and to make changes to the husbandry and early stage processing practices.

In order to make changes that are cost-effective and successful, the producer must be in a position to accurately identify blemishes and predict their impact on the finished leather value. However, because of the subjective nature of the assessments, the lack of a permanent record and the very limited body of information relating raw skin appearance to finished leather quality, both identification and estimation of the significance of blemishes was highly variable. Therefore, the objective was made to capture a pictorial record of a batch of skins in the raw state, in the partially tanned state (‘wet blue’) and as finished leather and prepare a reference catalogue for producers.

5.2 Methodology

The approach taken was to photograph the blemishes on a batch of 100 raw preserved skins prior to dispatch to a processor in Japan; to intercept them at the partially tanned state during the Japanese visit; and again as the finished leather in transit through Australia to their final destination. The views of the processor on these and other skins were also obtained.

5.3 Results and Discussion

Approximately 1000 digital images were collected of 20 raw skins from the batch of 100 bearing various faults. The corresponding partially tanned (wet blue) and fully finished leather was also photographed as far as possible, and assessed for their value in informing the producer about the appearance and consequence of various blemishes.

Five examples of faults of interest that could be tracked and where images were sufficiently clear are presented below, as pairs of pictures of an area of raw skin and the corresponding finished leather. The images of wet blue were of limited value because of practical difficulties and are not included. This may in fact be a preferable point at which to compare the raw skins as the chrome tanned leather (either in the wet blue or dried state) is of uniform colour and surface gloss, and defects have not yet been hidden.

Figure 21 illustrates the effect of brown spot (a common bacterial infection) on the raw skin (left) and the finished leather. Even relatively minor lesions can cause severe pitting in the grain surface that is a major contributor to loss in value. Also evident is a tooth cut that when processed to finished leather created a hole. This would also result in complete loss of this area of the leather at significant cost.

Figure 22 illustrates the effect of recently healed teeth marks (left) in the final leather (right, arrowed), where they are clearly visible after finishing. Falling as they do in the central area of the main panel, the scars would have maximum negative effect on the value of the skin.

Figure 23 shows one area of severe scale erosion analogous to brown spot (Fig. 21 above), which results in a badly pitted grain surface (right, arrowed). However, other areas of scale erosion, particularly where it is associated with sloughing or abrasion, may look poor but nevertheless hardly affect the finished leather. It is important to be able to distinguish the cause and depth of damage to determine whether it is a high priority for remediation.

Figure 24 shows the phenomenon of ‘double scaling’ which appears to be due to retention of partially sloughed scales as the new scales are growing. It results in a distinctive crescent or circular impression in the finished leather (right, upper edges of scales) and may cover much of the skin area. Also present are numerous eroded and scarred areas.

Figure 25 demonstrates how even fully healed and very faint scars can still appear in the finished leather and oblige the tanner to apply a heavier or more opaque finish than would otherwise be needed. It is essential that as far as possible, cuts and lesions be prevented as even faint blemishes will show clearly in the most valuable pastel-coloured or lightly finished leathers.

The development of a catalogue of faults to provide some guidance to producers was heavily constrained by a number of factors. As this objective was added to an existing project at short notice and with very limited resources, it should be viewed as a pilot exercise to explore the value, feasibility and logistics of a larger effort.

A handheld digital camera and flash or ambient lighting was used. This resulted in many images being of limited value because of flaring and shading effects. Photography of this type of substrate is very problematic and requires specialised equipment and controlled conditions.

Unfortunately, it was not possible to influence the finish applied to the various skins as the coating, colour and pigment were selected by the processor to hide the defects observed as far as possible to try to improve the leather value. Thus the surface gloss, opacity, depth and colour vary drastically from one sample to another and make photography very difficult. This illustrates very well how faults in the skin result in the processor having to apply more time and resources to produce a lower value, more heavily finished leather.

The skins were sampled at only one time in the year, when the production schedule was least appropriate and at only one producer. A selection of times more appropriate to realistic production timetables and a broader representation of producers would ensure that the skins would be more representative of the range and appearance of the various faults. A future exercise should seek to conduct the photography in a studio environment.

5.4 Conclusions and Recommendations

Despite the limitations of the present study, the results were very well received by industry and support exists for a more comprehensive effort. A preferable approach might be for a project to acquire all of the skins necessary and record good quality images of the raw skin faults. The skins could then be processed under contract to a uniform colour and finish, selected for the clarity with which faults are visible, and returned for final imaging. As the process is non-destructive, skins could be sold, faults, finish and colour notwithstanding, to recoup some of the cost.

6. Quality Management

6.1 Background and Objectives

The Quality Management System (QMS) of an organisation is the management mechanism to ensure that the activities necessary to deliver products or services that are to the customer’s satisfaction take place and are efficient and effective.

The ISO 9000 – 2000 series of standards specifies requirements for a QMS “where an organisation a) needs to demonstrate its ability to consistently provide product that meets customers and applicable regulatory requirements and b) aims to enhance customer satisfaction through the effective application of the system including process for the continual improvement of the system and the assurance of conformity to the customer and applicable regulatory requirements.”

The standard is applicable to any organisation regardless of type, size and product provided. As a result of the revisions for the 2000 version, the standard requires a minimum of documentation and recognises that some parts are not applicable to certain organisations. Thus it is much less onerous and more instructive than the 1994 version. Although relatively few organisations require a registered ISO 9000 standard QMS in order to operate, many have found it valuable to implement the process formally, and very many informally, because it provides a useful framework for reviewing and controlling the business operation.

The eight principles upon which ISO 9000 is based are:

• customer focus to ensure that current and future needs are known and expectations met or exceeded • process approach to operations to ensure efficiency and coordination of activities • fact-based decision making using reliable, valid data and information • leadership of management in ensuring a single, coherent and understood direction • involvement of all levels in the organisation to achieve the purpose of the organisation • system approach to management and coordination of the various production processes • continual improvement as an organisational standard • mutually beneficial relationship between an organisation and its suppliers and customers

In the present context, the ISO 9000 standard is used as a template in briefly reviewing the quality management requirements in crocodile skin production. The objective is not to advocate the introduction of a QMS or of ISO 9000 accreditation but to indicate where quality problems may exist and provide an outline for solving them. The current project was established primarily to improve the processes entailed in producing crocodile skins and hence an emphasis is placed only the first three of the principles. More details on methodology and implementation are available from the ISO 9000 series documentation and the general literature.

6.2 Observations and Recommendations

6.2.1 Customer focus

The ISO 9000 standard does not mandate a particular quality but rather focuses on the customer’s requirements. These may include compliance with the customer’s own standards or with national or international standards, or amount to acceptance of the producer’s standards. Insofar as the grading of crocodile skins is set or agreed by the customer and a price paid accordingly, it is the customer’s standard that is in effect.

The visit that was made to the overseas processor, noted at various points in this report, was invaluable in providing information that assisted directly in the achievement of the objectives of this project. It also amply illustrated the necessity to develop a good understanding of, and a determination to meet or exceed, the customer’s requirements. Although the processor (tanner) is a key customer, the other ‘customers’ in the path from skin producer to the purchaser of leather products (‘end user’) should also be kept in mind by the producer. As the only step in the process path where skin quality can be improved and where decisions affect all other steps in the path to the end user, the producer has a unique opportunity to influence quality and returns for himself and others and the unique task of understanding the needs of all customers.

Although they may be the producer’s direct customers, skin traders should have relatively little impact on the quality of the skins but rather translate the requirements of the processor to the producer. (The exception is if the trader mishandles the skins and causes degradation). Processors however are directly and strongly affected by the decisions taken by the producer, from the diet to the husbandry to the age at slaughter to the preservation. Producers should therefore place great emphasis on establishing good relations with the processors of their skins and gaining a technical understanding of the processes used and constraints faced and hence the significance of the customer’s needs. Beyond the processor, the manufacturers of leather products and the final buyers should also be considered important customers and their needs addressed as far as possible.

6.2.2 Process approach

As the ‘process approach’ is considered central to quality management, the ISO 9000 standard emphasises and mandates six procedures and these are outlined here as a framework for discussion of the crocodile skin production operation.

• Document Control

The initial establishment of a quality management system entails the writing of a ‘quality manual’ which sets out exactly what the organisation does. In addition to the formal documentation regarding ISO 9000 accreditation etc, it must include all operations, procedures, standards, test methods and documentation records.

In the current context, the quality manual would be a detailed description of the way each operation is conducted. Crocodile skin production was observed to be especially apt to benefit from the existence of written procedures. This is because the operations are almost entirely manual, often performed by recently employed staff, rarely intuitive or obvious and so prone to error, and the consequences of error are often not immediate but can be very costly.

Even where ‘errors’ are not made, the lack of a written process or example of how an operation should be performed or how the result should appear can result in a gradual drift away from the intended process. For example, the skinning operation requires a particular sequence and depth of cuts, and decisions regarding the positioning of the cut when scales are uneven. A document describing the skinning operation would open with a description and diagrams or pictures of the objective, in this case a skin cut to a particular size and shape, free of nicks and scores. It would

include the reasons for this objective (the value to the customer depends on being able to cut large square areas free of cuts or scores) and the consequence of non-compliance (substantial loss of skin value). The document would give explicit instructions on how to achieve the objective, including the actions to take when difficulties are encountered. For example, it might specify and show that where an uneven scale is encountered, it should be left with the skin rather than with the backstrap as this results in a smaller overall loss of value.

As new staff are employed, the training process could be significantly hastened and fewer errors made if it included a detailed instruction manual. Existing staff returning from leave, or needing to check that their technique was not drifting away from the objective, could also refresh their knowledge without any implication of ineptitude or error. Scope for misunderstanding and disagreement would also be reduced.

The preparation of written procedures for all operations, eg egg collection, skinning, meat packing, covering all processes, eg husbandry, abattoir, skin business, is very strongly recommended. However, beyond the preparation of the initial documentation, the other emphasis of ISO 9000 is ‘document control’ or ‘version control’. That is, ensuring that all staff are actually using the same process. This is particularly problematic where processes are changed or developed and only verbal instruction is given as it is difficult to ensure that the new procedures are communicated correctly and to all staff, that they are remembered or implemented and that they are passed on to new staff. Version control requires that any changes to processes be written down and appropriately referenced and circulated to all staff, and that earlier versions be removed and isolated or destroyed.

• Record Control

Very strong emphasis is also placed on the creation and maintenance of records, without which the organisational memory quickly disappears and achievement, proof and sustainability of quality improvement become almost impossible. Records should encompass the history of all processes and their outputs including test or assessment results and verifications. Some of the benefits of good record keeping are; to allow systemic problems to be identified quickly, to provide information to demonstrate whether or not a change is beneficial; and as a defence against unfounded damages claims from customers. For example, the ability to retrieve records showing how and when particular skins were preserved, what other skins were processed in the same way and what results achieved, can provide concrete proof that the process is effective and not the cause of claimed problems.

The CITES mechanism of tagging skins is uniquely suited to establishing reliable and detailed records of skin quality and measurements because it is mandatory and traceable. If allied with husbandry and skin processing data on one hand, and sales and customer data on the other, a comprehensive database would provide crocodile skin producers with a very powerful business and quality management tool.

• Internal audit

The purpose of internal auditing is to ensure that the processes and procedures that are intended to be in use are actually operating correctly. Over time, and especially if processes are altered a number of times or priorities and pressures change, compliance with specifications deteriorates.

Thus it is important to review entire processes from time to time to re-establish or reinforce standards and identify problems.

• Control of non-conformance • Correction • Prevention

The final three procedures deal with handling products or operations that have been found to fall below the acceptable standard, correcting both the effect of the problem and the immediate cause, and preventing a recurrence through systemic improvements. Thus for example, skins that are found to be inadequately preserved would be isolated from the main production stream (‘controlled’). They would be checked for damage and, if acceptable, re-treated, with the process itself being re-established according to specification (‘correction’). Finally the process would be reviewed to identify the systemic cause of the problem eg a changed chemical supplier resulting in altered concentrations or labelling of chemicals, and action taken to prevent further errors (‘prevention’)

6.2.3 Fact-based

Research involving a discrete natural product such as a skin (as distinct from a bulk product such as cotton that can be blended, divided, sampled etc) encounters the major obstacle that every skin and each part of every skin is different. Subdivision of the skin causes substantial changes to behaviour and blending and sampling can be meaningless. The problems are greatly exacerbated in the case of crocodile skins because of their high value and extreme variability from point to point, and because some effects such as the shrinkage problem discussed above, occur over weeks or months. Very careful experimental design and interpretation is therefore required to ensure that the data collected is true and the conclusions drawn are valid.

In the skin production environment, it is extremely easy to attempt to solve a problem by making instant changes to the process or procedure and interpreting any improvement as the consequence, when it may be that the problem has disappeared coincidentally. Many problems are naturally transient. A failure to analyse the problem thoroughly; to plan the tests to prove the analysis and identify options; and to verify the solution, can result in the process lurching from one problem to another, many of them caused by previous solutions. Often, the process itself accumulates activities that have no purpose other than that they were introduced as solutions to problems and are continued thereafter. Removing processes or treatments can sometimes be the most beneficial action to take.

In order to make steady, verifiable improvement to the quality of production, the existing processes and procedures should be stabilised, preferably in their simplest acceptable form, and no further changes made. This can most easily be done through the ISO 9000 documentation template. Once documented, no change should occur either to simplify the process, to solve problems or to improve quality, unless it has been analysed and proven as noted above. Once it has, the documentation should be updated to a new version and the old version withdrawn.

Any attempt to stabilise and improve quality, and indeed to conduct scientific research, will be confounded by a background of frequent, planned and unplanned, minor and major changes to the processes in operation. Stabilisation is essential and once stabilised, even at a sub-optimal level, no changes should occur unless they are based on factual data. Although progress may appear slow in the short term, it will continue and be substantial in the long-run.

7. Conclusions

The objectives of this project, initially and following identification of additional problems, were to:

1. reduce labour costs of fleshing by at least 50%, whilst ensuring that the methodology was not damaging the skin, and preservation was maintained

2. improve the average grade of the skins by at least 10 percentage points (e.g. 1st grade from 20% to 30%) through improved fleshing, preservation and storage processes and to eliminate these operations as a cause of downgrading

3. stabilise the width of the skins at a point significantly above their minimum without disrupting the pricing mechanism and thereby losing any benefit. The objective was set to achieve a 5 percentage point average increase in width accepted by the processor and with no negative pricing signals

4. capture a pictorial record of a batch of skins in the raw state, in the partially tanned state (‘wet blue’) and as finished leather and prepare a reference catalogue for producers

5. indicate where quality problems may exist and provide an outline for solving them.

Objective 1 was achieved by eliminating the fleshing process entirely. This demonstrated the value in reviewing operations to determine whether they are in fact necessary, beneficial or profitable. There are several strategies to determine this including careful experimentation, logical analysis and market information. The route taken was to gather market data that could be relied on to be free from misinterpretation and bias and this proved very effective.

Objective 2 required the development of preservation and storage processes that were specifically suited to crocodile skins and that could be relied on to protect them for the anticipated time and conditions of storage and transport. The time required for the various experimental trials illustrates the necessity to ensure that a process be fully tested under the most harsh conditions that might be experienced to ensure that it is going to be robust in an industrial setting.

Type of Faults May 03 (n=100) 80% 70% 60% 50% 40% 34% 25% 30% 20%

Percentage 20% 14% 8% 10% 0% No faults Infections Scars Double Inf ec t. + scale scars Fa ults

Figure 26. Assessment of fault frequency in a batch of 100 skins (May 2003)

Early in the project, the cause of skin faults for a batch of skins was assessed (Fig. 26) and the resulting grade distribution recorded (Fig. 27) to provide a benchmark for improvement. The great majority of the faults were related to husbandry issues that were outside the scope of the project although advice was provided where appropriate.

Average Grade of Skins May 03 (n=100) 80% 70% 65% 60% 50% 40% 30% 22% 20% Percentage 13% 10% 0% Grade 1 Grade 2 Grade 3

Figure 27. Grading outcome (only 3 grades utilised) for a batch of 100 skins (May 2003)

The causes of skin faults for a batch in the following year (Fig. 28) show a marked improvement, primarily through a reduction in infections. Of particular interest was the appearance of a new fault of ‘wrinkle’, manifesting as very thin, papery scales that were prone to wrinkling during preservation. The underlying skin appeared to be relatively soft and spongy although no information as to the consequences for the finished leather could be acquired from processors in the time available.

Types of Faults March 04 (n=100) 80% 70% 60% 50% 38% 40% 28% 30%

Percentage 20% 5% 13% 9% 10% 0% No faults Infections Scars Infect. + Wrinkle Fa ults scars

Figure 28. Assessment of fault frequency in a batch of 100 skins (March 2004)

Figure 29. Raw skin showing wrinkle

The cause of wrinkle (Fig. 29) was identified as an un-trialled change to the process introduced in order to reduce the incidence of infections. Advice was provided on the appropriate treatment and the fault subsequently disappeared.

Despite the occurrence of wrinkle, the grade distribution (Fig. 30) for the sample batch of skins of March 2004 demonstrated a marked improvement over the outcome of the previous year. It is not possible to identify how much of the improvement is a consequence of the efforts by the producer and how much, if any, is a result of the direct or indirect influence of the project. Although extremely welcome, the changes highlight the difficulty of developing improved processes against a changing operational background where it may be impossible to definitely identify causes of problems or benefits of proposed solutions.

Average Grade of Skins March 04 (n=100) 80% 70% 60% 50% 40% 32% 33% 34% 30%

Percentage 20% 10% 0% Grade 1 Grade 2 Grade 3

Figure 30. Grading outcome (only 3 grades utilised) for a batch of 100 skins (March 2004)

Objective 3 was introduced during the project as the problem of skin shrinkage was identified. It is clear that shrinkage is detrimental to the producer and possibly also to the processor who may not be able to recover the area of an over-salted or over-dried skin. Use of a 60% brine solution in conjunction with a preservative gives rise to a contraction in width from the raw to the preserved state that is 5 to 6 percentage points less than caused by solid salt or saturated brine whilst also allowing the skin to be handled, graded and measured easily. The width of the preserved skin appears to be stable over time, where salted skins may continue to contract.

The change is brought about without generating any negative pricing signals from the market. Some loss of area from the raw skin state is probably unavoidable in order to arrive at a stable, preserved condition. More strenuous efforts to increase width should beware of provoking a reduction in price due to processors achieving lower leather yields from overstretched skins. As it is, there may be an additional benefit to the processor in terms of leather yield from 60% brined skins compared with

skins that have been 100% brined or salted, (including the effect of storage and drying) although this would require further study. If this proves to be true, some benefit may flow back or be recoverable by the producer.

Objective 4 was also introduced during the project as it became evident that concrete information was lacking on the identity and causes of various skin blemishes, and their effect on the finished leather and hence skin value. The task was logistically very difficult given the limited resources and time frame, and the outcome should be viewed as a pilot study for a more developed project. Nevertheless, the result demonstrated the value of the approach in informing producers as illustrated by the response received on presentation to the 17th IUCN Crocodile Specialist Group Working Meeting, held in Darwin 24th – 29th May 2004.

The photographs demonstrated the need to identify particularly deleterious faults such as brown spot and the need to prevent or heal these. In addition, even fully healed and faint scars often appeared clearly on finished leather, demonstrating that the priority should lay in preventing damage from occurring rather than trying to repair it after the event. Severe scratching will permanently degrade a skin and consideration should be given to the continued cost of keeping a scratched animal against the likely return for a low grade skin.

Given that the farming of crocodiles exists, in part, to supply the demand for skins and thereby to support the protection of native crocodile populations, it is considered essential that the farm producers receive and respond to the market signals. They should seek to be the suppliers of the best and most consistent product so that poaching is a less economically viable source of skins. Producers may send off their raw skins and never see the resulting products, thus it is useful to have a pictorial guide to demonstrate for example, that the faint healed scar on a raw skin resulted in a clear fault in the finished leather which reduced its value to the end user, and hence the return to the producer. Some information on the likely causes and means of preventing some forms of damage would be a useful accompaniment to a future guide.

Objective 5 entailed a brief review of the quality management issues of crocodile farming and implementation of the various process changes recommended through this project in the ISO 9000 style. It was found that crocodile farming is a complex activity with a range of systems, operations, processes and procedures. In addition, much of what is done involves poorly defined environments and materials, uncontrolled and variable conditions and demands, and a mobile workforce. Under these circumstances, an ISO 9000 quality management approach is considered ideal for establishing a level of stability and control within an otherwise chaotic environment.

In order to establish and sustain a quality management regime, whether or not it is modelled on or implements the ISO 9000 standard, it is essential that management at the highest level commit to it fully. Any new process, whether scientifically founded or ad hoc, that is put in place without a supporting structure will degenerate and the benefits be lost. Untested changes or errors will creep in, procedures will be forgotten or misinterpreted and testing and record keeping will cease. It is not recommended that the full ISO 9000 implementation be pursued unless there is a clear market benefit to this. Rather, the procedures and requirements provide a very valuable template for relatively easy and gradual introduction of procedures and controls.

Appendices

Appendix 1 Short-Term Preservation Procedure for C. porosus Skins

1. This procedure assumes that skins weigh on average approximately 2 kg. If the average differs from this by more than 10%, adjust the amounts used accordingly.

2. Skins preserved using this short term preservation process can be stored up to 5 days in cool room (4oC) or 2 days at room temperature.

3. Estimate the number of skins to be produced on the following day, and their weight.

4. If space and facilities permit, prepare 60% brine in bulk and use as required. If not, then at least one day before skinning, prepare enough 60% brine solution using clean salt to give 4 litres of brine for each 2 kg skin (refer to table below). Before use, confirm that brine is 60% saturated using a Salinometer or other appropriate test device.

5. Store brine to be used next day in cold room overnight. Twelve to 24 litres per container (3 to 6 skins) is a convenient size for treatment and handling.

6. Within applicable food hygiene guidelines, carcases can be swabbed after slaughter as thoroughly as possible with appropriate disinfectant, paying particular attention to axillae, cloaca and incision areas.

7. To chill, carcases should be hanged, well separated, in cold room overnight to cool as rapidly as possible.

8. Place each skin directly into cold brine, after removal from the carcase. Stir and submerge it for 5 minutes and leave overnight or until proceeding to long-term preservation.

9. Skins can be removed from liquor for measurement, trimming, grading etc, preferably after at least 4 hours. They can then be returned to the liquor for further preservation or storage.

10. If it is necessary to drain skins, stack them grain side down on an inverted V tray and leave covered in a cool, draught free area. Do not allow to dry out. Proceed to long term storage as soon as possible.

Preparation of 60% saturated brine solution No. of skins Water (litre) Salt (kg) 1 4 0.9 2 8 1.8 3 12 2.6 4 16 3.5 5 20 4.3 6 24 5.3 7 28 6.2 8 32 7.0 9 36 7.8 10 40 8.8

Appendix 2. Long-Term Preservation Procedure for C. porosus Skins

1) This procedure uses a commercially available biocide in concentrated form and requires appropriate occupational hygiene and wasted disposal precautions. Please refer to suppliers instructions prior to implementation.

2) Wear rubber gloves and safety glasses when handling concentrated biocides. Use a mixing jug and a graduated cylinder specifically designated and labelled for this and used for no other purpose. Wash hands thoroughly after handling. Store the biocide in a non-food cold room when not in use to maintain maximum activity. All preservation operations should be conducted in a designated area away from food processing areas and live animals.

3) The product indicated is Preventol WB, supplied by Bayer Ltd. This is an example of a suitable product only and is neither intended to endorse this product nor to limit use of alternative products.

4) Proceed as for short term preservation. After the skins have been soaked for at least 4 hours in 60% brine, remove them from the liquor and place in another bucket.

5) Measure out Preventol WB at the rate of 8.4 ml per skin using a measuring cylinder and dilute 1 in 10 with water into a 2 litre plastic jug (refer to table below).

6) Add the diluted Preventol WB to the 60% brine solution and stir thoroughly.

7) Put all the skins plus any drained brine liquor from the bucket back into the brine and Preventol WB solution.

8) Stir for 5 minutes and then 1 minute every hour for the next 4 hours. Leave at least over night and for up to 2 days.

9) Remove skins from liquor, spread on inverted V tray, cover and allow to drain for 4 hours in cool, draught free area. Fold with flanks spread out flat and seal in individual plastic bags.

10) Store in cool, dry area or cool room.

11) Dispose of exhausted liquor as appropriate for local regulations.

Quantity of Preventol WB required No. of skins Preventol WB (ml) Dilute with water (ml) Add to brine (litres) 1 8.4 84 4 2 17 170 8 3 25 250 12 4 34 240 16 5 42 420 20 6 50 500 24 7 59 590 28 8 67 670 32 9 76 760 36 10 84 840 40

Appendix 3. Sources

1. Personal Communication with Mr. John Lever, Koorana Crocodile Farms and Queensland Industry Association Representative. (Extensive industry background, production and processing information and problems)

2. Ms Catherine Money, OIC, CSIRO Leather Research Centre. (Crocodile skin processing industry issues and problems)

3. RIRDC Database of Current and Completed Research on C. porosus

• DAQ-258A “Market Characteristics and Opportunities for Skin Products of Emerging Animal Industries” (relevant to industry views and issues) • DAQ 188A “Crocodile Farming - Research, Development and on Farm Monitoring” (general background information) • UJC-5A “Skin Diseases of Farmed Crocodiles” (relevant to skin damage from Dermatophilus sp.) • WMI-1A “Improving the Quality of Australian Crocodile Skins” (relevant to issues relating to skin value and scale pattern) • DAQ-247A “Improved Nutrition and Management of Farmed Crocodiles – from Hatching to Harvest” (information on skin quality and stocking levels, fungal infestation etc) • DAQ – 229A “Crocodiles Restraining and Meat Quality” (relevant to handling and slaughter damage of skins)

4. Crocodile Specialist Group (CSG) (http://www.flmnh.ufl.edu/natsci/herpetology/crocs.htm (Database on world production and conservation issues.)

5. European Patent Organisation (http://ep.espacenet.com). (Patent on fleshing of cattle hides using enzymes (DE 42 12 568, 1993)

6. World Bank Report on food contamination (1997), (http://wbln0018.worldbank.org/rdv/animal.nsf/ ad4d7220ed799d3b852566900057ac46/eab07f85136e7f5e852566cd0054c664?OpenDocume nt#sum (Covering, inter alia, alternative livestock production, makes mention of the very effective hygiene methods used in Australian crocodile skin production and concludes that there is negligible public health risk from crocodile meat.)

7. Agexporter Journal, May 2000 (http://www.fas.usda.gov/info/agexporter/2000/May/cajun.htm) (Quotes Mr. Bernard DeReynies, (CEO of Roggwiller Tannery of Louisiana (RTL) which processes 60,000 alligator skins pa) places C. porosus skins in first place, as far as price classification, followed by US alligators.)

8. Australian Senate Rural and Regional Affairs and Transport References Committee “Commercial Utilisation of Australian Native Wildlife”, June 1998, Chapter 11 (Crocodiles) http://www.aph.gov.au/senate/committee/rrat_ctte/wild/contents.htm (Gives a background to environmental, economic and political issues.)