Dried, Cured and UNIT 6 DRIED, CURED AND SMOKED Smoked Products PRODUCTS

Structure 6.0 Objectives 6.1 Introduction 6.2 Cured Products in Indian Economy 6.3 Traditional Methods and Products of India 6.3.1 Quality of Cured Fish Products 6.4 6.4.1 Quick Salting Process 6.5 Drying 6.5.1 Fundamentals of Drying 6.5.2 Sun Drying 6.6 Microbial Spoilage 6.6.1 Red Halophiles 6.6.2 Dun and Fungal Attack 6.7 Insect Infestations 6.7.1 Losses due to Insect Infestation 6.8 Packaging and Storage 6.9 6.9.1 Preservation Objectives 6.9.2 Smoke Production 6.9.3 Smoke Components 6.9.4 Quality, Safety and Nutritive Value 6.9.5 Processing and Equipment 6.9.6 Pre-smoking Processes 6.10 Let Us Sum Up 6.11 Glossary 6.12 Suggested Further Reading 6.13 References 6.14 Answers to Check Your Progress

6.0 OBJECTIVES

After reading this unit, you will be able to:

 discuss on methods of production of cured and smoked products;

 summarise the process of salting and drying;

 explain the packaging methods of such products; and

 describe storage and shelf life of these products. 25 Fishery Products 6.1 INTRODUCTION

The importance of fish and fish products as a rich source of well balanced proteins, their importance as a source of health food, as an ingredient of feed of other animals and as aquaculture feed has already been discussed in the earlier units on Products of commerce. However, fish is highly perishable and needs short term as well as long term preservation. It is in this context the importance of preservation of fish by traditional methods becomes relevant. Preservation of fish by sun drying, salting, smoking, acid curing or a combination of these methods forms the basis of preparation of traditional fish products of many countries. You must realize that Asia is by far the largest producer of cured fish products. Amongst the highest producers in Asia are China, Japan, Indonesia, Philippines, India and Korea.

6.2 CURED FISH PRODUCTS IN INDIAN ECONOMY

You will be surprised to know that till 1959, about 50% (about 0.5 million tonnes) of marine fish landed was utilized for curing. In subsequent years, share of cured fish started declining. At present, about 12-15% of marine fish landed is processed by traditional methods. Certain sections of the consumers of the country have developed a preference for such products on account of their taste and flavor. In addition, these products cater to the need of weaker sections of Indian people.

6.3 TRADITIONAL METHODS AND PRODUCTS OF INDIA

You should know that traditional methods which are almost exclusively based on marine fish and extensively followed in India are:

a) Sun drying,

b) Dry salting and mona curing,

c) Wet salting,

d) Pit curing,

e) Colombo curing, and

f) Smoking and drying (Mas-meen).

In all these cases, excepting the last one, raw are subjected to processing; Mas-meen is based on which is cooked prior to further processing. Colombo- curing and pit-curing of fish have become extinct in India and at present are of historical importance.

Methods followed for the preparation of different products have been adequately described by many researchers.

26 Basic principles of the different methods for traditional products are given Dried, Cured and below: Smoked Products a) Sun drying: Fish are hard dried in direct sun. No prior salting is carried out. b) Dry curing: is added to dressed fish. The salt fish ratio varies but is usually 1:5. Salting period is normally 18-24 hours. is lightly washed, drained and dried in sun.

In mona curing, guts and gills are dexterously pulled out through mouth cavity; fish is salted (1:4) for about 20 hours, washed lightly and dried in sun. c) Wet salting (also known as Ratnagiri method): Salt to fish ratio is normally 1:3. Fish with salt is kept stacked allowing the self-brine to drain out. The salted fish is marketed without sun drying. d) Pit curing: Fish is salted in 1:4 ratio, bundled up in palmyra leaf and kept buried under in pit for three days and then removed. No sun drying is done. e) Colombo curing: Dressed fish is mixed with salt (1:3 ratio) and gorukapuli (Malabar tamarind, Garcinia combogia), and is kept stacked in cistern (weighted down). After a few days, fish is repacked in a suitable container which is completely filled with self-brine and closed air-tight. f) Smoking and sun drying (Mas-meen): Tuna fish (Family: Scombridae) is eviscerated, filleted into chunks and cooked in light brine. Cooked chunks are directly hot smoked in a traditional kiln with coconut leaves and then hard dried in sun. 6.3.1 Quality of Cured Fish Products

During the last fifty years or so, extensive and periodical investigations on the quality of cured products involving large number of samples collected from different centres both of East and West coasts have been carried out. Quality is judged by the determinations of moisture, , acid insoluble ash, total volatile base and occasionally, trimethylamine nitrogen. Microbiological study carried out in some cases was confined mainly to determination of total plate count and to pink discoloration.

6.4 SALTING

Salting, you see is a method to preserve fish. It may form a part of the process prior to sun drying and/or smoking. Different traditional methods of salting which are differently named in different countries may be divided into following three main categories. Fish is ordinarily dressed or filleted before salting. a) Kench curing: In this method, dry salt crystals are applied to the flesh side of dressed fish and fish is stacked. As the salt penetrates the flesh, the extracted moisture is allowed to drain away. The method is suitable for lean fish and cannot be successfully used for fatty fishes such as sardine and 27 Fishery Products due to oxidation of fat by atmospheric oxygen giving rise to rancidity.

b) : This is also a dry salting method in which the moisture extracted while the salt is penetrating the flesh, is not allowed to drain out. Thus, fish subsequently remains immersed in the self-brine.

c) : This is a wet salting method in which fish is soaked in a concentrated saturated salt solution.

Pickling and brining are advantageous for fatty fish since being immersed in brine, fat is protected from atmospheric oxygen.

Salt penetration depends upon the condition of fish; those in rigor take longer to salt than those in the first stage of autolysis. This is obviously due to change in the tissue structure. In addition, from public health consideration, only fresh fish should be used for salting. 6.4.1 Quick Salting Process

Traditional method of salting fish takes a long period (not less than 24 hours) to achieve the equilibrium concentration of salt in the flesh even when a high ratio of salt to fish (1:4 by weight) is used. It is due to the thickness of flesh; as in traditional practice, dressed whole fish or thick chunks of flesh are subjected to salting and salt has to diffuse through a long distance. A shorter period to complete salting and/or drying is more suitable for large scale production or mechanization of the process.

During late 1960’s, a few new techniques for salt curing of fish were developed with the purpose of completing, the salting process in a short period of one hour or even less. Of all these techniques, Del Valle Nickerson method is of great practical value. In this method, commonly known as quick salting method, skinned fish flesh is ground with simultaneous addition of salt (20-100% of fish by weight). This increases the surface area of the fish and decreases the diffusion distance, thus increases the salt penetration rate and reduces the period of salting. The mix is further ground to distribute salt and fish uniformly. Fish and salt mix is next pressed to remove water and to get the pressed material in the form of a cake. The cakes are subsequently dried. Sun-drying keeps the cost of processing low.

One reason for the success of the process is the use of optimum ratio for common salt to fish muscle. The ratio varies from species to species. Too low or too high salt to fish ratio does not result in good cake-formation. Too low salt to fish ratio produces a gelatinous mass which does not allow proper separation of water and its pressing out. Too high ratio gives brittle cakes. An optimum salt to fish ratio gives well-pressed, highly compact and non-brittle cakes. The press- cake may be dried in sun or in a hot air dryer; the temperature of air should not exceed 45°C; otherwise the cake would disintegrate.

The technique of quick-salting is quite simple and requires only a few easily available processing equipments. It can be easily adapted in the small scale sector and can be operated by the fisherman community who are familiar with traditional method of salting and sun drying.

28 Dried, Cured and ? Check Your Progress 1 Smoked Products Note: a) Use the spaces given below for your answers. b) Check your answers with those given at the end of the unit. 1) What is the share of fish processed after landing? ...... 2) Name a few traditional methods of curing of fish? ...... 3) What are the three main categories of salting? ...... 4) Name a new method of salting developed in late 1960s? ......

6.5 DRYING

Salting alone does not allow long term preservation of fish and therefore most salted products are dried to bring down their water activity sufficiently low to have micro-biological stability. In India, Bombay-duck (Harpodon nehereus) and white bait (Anchoviella spp.) are dried without prior salting (Fig.6.1).

Fig. 6.1: 6.5.1 Fundamentals of Drying Drying of fish muscle can be divided into two distinct broad periods: constant rate period and one or more falling rate periods. 29 Fishery Products In the first period, the initial rate of drying is determined by the conditions of external ambient atmosphere such as its temperature, wet bulb depression, air velocity, direction of air-stream, shape and area of the surface. The period during which these conditions are dominant and which is known as constant rate period ends when the supply of water to the surface of the material (fish) is no longer capable of supporting the rate of evaporation. The second period termed as the falling rate period starts after the constant rate period. Rate of drying now decreases continuously until finally it becomes vanishingly small. 6.5.2 Sun Drying Natural drying in sun (Fig. 6.2) is totally weather dependent and is carried out by placing the product on the ground, mats or racks in sun and relies on air circulation to evaporate and remove moisture. This is the most common method followed by fishermen. If placed on the ground either directly or indirectly (i.e., on mats etc.,) solar energy supply takes place both directly and also through the heated ground floor. Once drying enters into falling-rate period, temperature of ground plays an important part as it supplies the energy for diffusion movement of water from the interior to the surface. Trials have been made to utilize the solar energy in a more efficient way. A black surface absorbs the heat radiation of the sun in a most efficient way and thereby causes the temperature of such a surface to rise more, compared to that of a surface with any other colour. Thus, drying rate of a fish or a fish product would be more when dried on such a surface or with air heated with a black surface. The above principle has been utilized in different ways to increase the drying rate of fish with or without prior salting. a) Black platform: In this method, a raised cemented platform was covered with low density black polyethylene sheet and non-penaeid prawns were dried on the same. The rise in temperature on black polyethylene covered surface was between 17 and 25oC above ambient temperature which was between 30 and 35oC. After 6 hours, the moisture levels of materials on black polyethylene surfaces were 6.2%. b) Solar dryer: In a solar dryer, heat radiation from the sun is trapped by conduction process through the use of different simple devices such as blackened corrugated GI sheets which raise the temperature of air. An electrically run centrifugal air blower blows above hot air into a drying tunnel containing fish to be dried. The air current velocity is kept at 120m/min. for maximum efficiency. To achieve 20-25% moisture level, the salted fish dried in the dryer took only half the time needed in the conventional method. The product did not come in contact with any contaminating agent and moreover dried material need not be removed from the dryer during night or with the advent of rain. There was no need of providing any protection against birds and turning fish upside down. But the main problem of installation of such a dryer is the availability of electricity in remote fish landing areas or fishing villages and also the installation cost. c) Solar tent dryer: In the solar tent dryers, solar radiation is allowed to pass 30 through a clear surface which may be a transparent glass or polyethylene sheet and is absorbed by the black surface of the floor and the back of the Dried, Cured and dryer. The black surface has thus its temperature raised and this in turn raises Smoked Products the temperature of air inside the tent. While no wind blows through the tent, a draught is induced within the dryer due to the tent acting like a chimney, air being drawn in through vents at the base and exhausted through vents at the top of the dryer. Moisture removed from the fish during drying is either carried out of the dryer with exhaust air or condenses on the inside surface of the polyethylene sheeting.

Fig. 6.2 : Drying of fish

? Check Your Progress 2 Note: a) Use the spaces given below for your answers. b) Check your answers with those given at the end of the unit. 1) What are the factors determining the rate of drying? ...... 2) How can you utilize the solar energy in a more efficient way in drying fish? ...... 3) What is a solar dryer? ...... 4) What is the principle in the solar tent dryer? ...... 31 Fishery Products 6.6 MICROBIAL SPOILAGE

Bacteria which can grow in presence of high salt concentrations have long been well-known. Certain marine bacteria not only tolerate high salt concentrations but have specific requirement of the same. 6.6.1 Red Halophiles Halophiles are red bacteria, characterized by the production of intense red or pink pigments and hence known as red halophiles. From health point of view, red bacteria are non-pathogenic and harmless and these are strongly aerobic and hence seldom attack fish deeply immersed in pickles. Solar of India were found to have a high load of red halophiles. Halophilic bacteria of salt cured products are mainly derived from solar salt which is at present a commercial commodity of the past. Manufactured salt or rock salt usually contains few . These halophiles are most troublesome in wet stack stage in salting and drying process. They may grow on fully dried salted fish which is locally dampened. Then, these form red colonies. 6.6.2 Dun and Fungal Attack “Dun “is another type of spoilage that occurs in dry salted fish, mainly in light and medium cures. This shows up as small, brown, black or fawn coloured spots or tufts all over the surface of fish. These patches are in fact growth of halophilic or halotolerant moulds of Wallemia sebi (or Sporendonema epizoum). These moulds are strict aerobes. “Dun” does not decompose flesh or produce any odour. It does detract the appearance of the product and so the commercial value of the product. These moulds have an optimum RH for growth around 75% and fail to grow below +5oC. Their temperature optimum appears to be around 30 oC. Fungal infestation of traditional fish and other products of India and other tropical countries is a common phenomenon. In smoked and dried fish from tropical regions (Pakistan, Malaysia, Hong Kong, Thailand and Zambia), isolation of Aspergillus spp., Penicillium spp., Acremonium spp., Wallemia sebi and Sporendonema epizoum, have been reported. Fungal infestation of sun-dried and salt cured products poses a public health problem of possible contamination with mycotoxins particularly aflatoxins (a poisonous chemical toxin caused by the growth of fungi). Though no aflatoxin has been reported in Indian cured fish products and also in many studies, yet it may be proper to keep a constant vigil over this specific quality aspect of the products.

6.7 INSECT INFESTATIONS

Traditional cured fish products whether simply sundried or salted with or without sun drying stored at ambient temperature are quite often found to be infested with insects (beetles, mites and flies). The infestation takes place either during drying itself or through cross- infestation during storage. Initial infestation is usually due to invasion by flying or crawling adults which lay their eggs on partially or fully dried products.

32 6.7.1 Losses due to Insect Infestation Dried, Cured and Smoked Products The dried products can suffer considerable loss due to feeding by insects. Quantitative loss as high as 30% due to fly-damage which takes place during processing or as high as 50% due to beetle damage during storage for several months has been reported. Apart from the above quantitative loss, the insect infestation also causes fragmentation of the product thus reducing its commercial value. Additionally, insect and mite pests often transmit mould spores and the heat and the moisture produced by heavy infestations can create conditions suitable for mould growth in fish that has been previously dried adequately. On the whole, insect infestation reduces the quality of a product and ultimately makes it unfit for human consumption.

? Check Your Progress 3 Note: a) Use the spaces given below for your answers. b) Check your answers with those given at the end of the unit. 1) What are red halophiles? ...... 2) What causes Dun? ...... 3) Name a few fungus species isolated from market samples of Indian dried fish? ......

......

6.8 PACKAGING AND STORAGE

Dried and cured fish products are easily prone to fungus attack, insect infestation and rancidity development. Depending upon the moisture content of the product and the relative humidity of the environment, there may be absorption or desorption of moisture, affecting the quality of a product and creating problems in its transaction in trade. While selecting materials for packaging, the above factors and other functional requirements have to be kept in mind. But all these are of little consideration even in present day packaging practice of India where only locally available materials which do not add to the cost of the product in any 33 Fishery Products substantial way are selected and used. It is the cost/benefit ratio or the cost which a market can absorb, that decides the issue. For storing sundried salted Indian mackerel, a number of packaging materials namely leaf baskets (Fig.6.3), deal wood boxes, tin containers, bitumen or polyethylene lined gunny bags, craft paper and polyethylene bags of 400 gauges are used. Of these, gunny bags lined inside with 400 gauge polyethylene or unit packs in 400 gauge polyethylene stored in a deal wood box were found to be suitable in a comparative way. The others gave trouble in one way or the other (craft papers gets wetted by fish-oil, bitumen lined gunny bags taint the product with foreign odour and severe rusting was observed with tin containers).

Fig. 6.3: Traditional and modern methods of packaging of dried fish

Polyester/ polyethylene laminated pouches have been found to be highly suitable for hygienic retail packaging of cured fish products (Fig. 6.3). Gusseted type, polylined gunny or HDPE woven sacks which can hold 50 kg of dried fish have been found to possess good stack ability, attractive appearance and good acceptability.

6.9 SMOKING

Smoking of fish was an incidental occurrence when, in periods of wet or humid weather, fishermen had to resort to the use of open fires, rather sun and wind, to dry their surplus catch. It was much later that the microbicidal and antioxidant effects of smoke processing came to be understood and appreciated. Long before this, consumers acquired a taste for as a pleasurable alternative to the consumption of fresh fish and, by reducing the ‘severity’ of the process (i.e. the degree, to which the fish is salted, dried and smoked); such products have won even wider appeal.

Preservation is the prime objective of fish smoking in most parts of the world. This may be preservation for very long period as with Indonesian products, ikan kaju, or addition of an extra day or two on the expected shelf-life of fresh fish to allow it to be distributed to remote markets, or to keep it slightly longer during retail display.

Smoked fish is regarded as a special food item, to be consumed on special occasion, which is nevertheless inexpensive also. As such, smoking shows great potential as a technology which could be carefully managed to ensure the wider consumption of safe, high quality fishery produce.

34 6.9.1 Preservation Objectives Dried, Cured and Smoked Products The preservative effect of smoking on fishery produce is said to be due to a combination of the following four factors:

 Surface drying, which provides water activity physical barrier to the passages of micro-organisms and pathogens and a hostile environment for any aerobic microbial proliferation.

 Salting, which reduces water activityand inhibits the growth of many spoilage organism and pathogens. (although a reduction of water activity below 0.92 is required before this effect becomes significant and at this level the saltines may be too high, about 5% for consumer tastes).

 Deposition of phenolic antioxidant substance, which delays autoxidation (rancidity) of the generally highly unsaturated fish lipids.

 Deposition of antimicrobial substances such as phenols, formaldehyde and nitrites. 6.9.2 Smoke Production You will be surprised to know that in many part of the world, wood is used in preference to sawdust for smoking. This makes a hotter fire with less smoke. In a sawdust fire, unless there is a forced rapid flow, the air cannot easily get to the fire, so the sawdust smolders rather than burns. Higher temperature and more oxygen, waste these substances by oxidizing them to carbon dioxide and water. Modern smoke producers feed sawdust slowly onto a very hot surface, but worldwide, most smoke for smoking is still produced from simple fire. The fire is usually contained in a fire box. Wood shaving, when lit in a good draught, burn fiercely and start the smoldering process in the sawdust. Both shaving and dust should be dry and free from wood preservatives. Damp materials harbour moulds and the smoke will carry these onto the fish. Wood preservative may produce harmful smoke which might make the smoked fish dangerous to eat. 6.9.3 Smoke Components The source of the sawdust affects end product flavours. Hard woods, such as oak, hickory, cherry, apple and beech, burn to give a smoke with more phenols, which both preserve and give a characteristic, ‘medicated’ flavour to the product. Smoke is an emulsion of droplets in a continuous phase of air and vapours stabilized by electrostatic charges on the droplets. For flavouring, cooling and microbistatic purposes, the vapours are of greatest importance in smoking. The droplet phase, in fact, acts as a reservoir of volatile and non-volatile smoke components, releasing more volatiles as they are absorbed from the vapour phase. 6.9.4 Quality, Safety and Nutritive Value Control of smoke production parameters must be complemented by control of raw materials if a standard quality product is to be achieved. Since most of the smoke components found in a smoked fish product are absorbed by the surface and interstitial water of the fish muscle, it is important that the fish remains wet, at least for part of the smoking process. The rate of absorption of smoke phenolic 35 Fishery Products compounds by pre-dried fish is only 5% of that absorbed by wet fish. The objectives of modern smoking procedures should be to impart the desired sensory characteristics to the product uniformly, without undue variation from batch to batch and to extend product shelf-life whilst avoiding the deposition of known harmful ingredients such as carcinogens. Colour imparted to the fish by the smoking process is due to carbonyl amino reactions of the Maillard (a non-enzymatic browning reaction) type and has been correlated with a quantitative decrease in carbonyl group in the smoke. Appearance and texture of the smoked product are largely affected by the control of raw material quality and process parameters such as bringing treatment and air speed in the smoking kiln. However, there is evidence to suggest that some of the smoke components, for example formaldehyde, have a toughening effect on the muscle proteins. Shelf-life extension of smoked fish (Fig.6.4) compared with fresh fish is due to a combination of lowered water activity and the absorption by the product of bactericidal and antioxidant components of wood smoke. 6.9.5 Processing and Equipment The quality of the product reaching the purchaser depends on the freshness of the fish before it is smoked and the care taken in handling it, the smoking process itself and subsequent storage history. Most poor quality smoked fish is due to bad handling before or after smoking or use of poor quality fish. Adequate smoking is nevertheless essential for a class product that will keep well.

Fig. 6.4 : Smoked fish 6.9.6 Pre-smoking Processes These can be divided into splitting and cleaning, salting and hanging. i) Splitting and cleaning : Precise treatment depends on the product; care must always be taken not to bruise or tear the fish. All pieces of gut, gill and kidney must be removed. ii) Salting : Fish may be soaked in strong brine. Permitted colours may be added to the brine to intensify colour imparted by the smoke. The contact time depends on the size and fat content of the fish. (2-3% salt is the maximum required if the product is to be eaten as a main dish rather than a condiment). A 70-80% saturated brine (i.e. 80°) is the commonest strength used. Brine must be kept to strength and should be changed at least once per day. Frequent removal of scales and other debris is necessary. Fish can be contaminated by stale brine. iii) Hanging : Fish is hung to drip either on racks or in the kiln (Fig.6.5). Protein dissolves in brine to give a sticky solution. During the hanging period this dries on the cut surface and produces the familiar glossy skin. The best 36 gloss is obtained when 70-80° brine is used. Smoked fish which has not Dried, Cured and been salted, looks dull and rough. Smoked Products Smoking process control: It is best to keep the temperature in the smoke chamber below 30° C at the beginning of the smoking process. In fact, for cold smoking, the temperature is kept at this level throughout the process. This is because the process must dry the fish to a certain extent as well as deposit smoke on the fish surface. To achieve this, the air vents to the fire box should be almost closed so that the sawdust smolders rather than burns. If the air flow is too rapid and temperature is too high the surface becomes sealed off; no more water can be drawn out of the fish and the condition is called ‘case hardening’. Case- hardened material is wet under the hard surface and tends to spoil from the inside. The hard blocked surface does not allow passage inward of the smoke chemicals, again lowering the preserving effect of the smoking process.

Fig. 6.5: Smoking kiln Horizontal flow kilns (Fig.6.5) are often called mechanical Kilns because an electric fan usually draws the smoke along the rack of the fish. This can be used for both hot and cold smoking by the use of electrical heaters in the smoke chamber. In large kilns of this type, heaters may be placed at different points in the smoke path to keep the temperature more even throughout the smoke chamber. Chimney kilns are most often used for cold smoking, and squat kilns for hot smoking.

? Check Your Progress 4 Note: a) Use the spaces given below for your answers. b) Check your answers with those given at the end of the unit. 1) Which is the most suitable method of packaging of cured fish products? ...... 2) What is the prime objective of smoking? ......

37 Fishery Products 3) What is special if hard woods are used to produce smoke? ...... 4) What causes colour to the fish by the smoking process? ......

5) What all activities come under pre smoking process? ...... 6) What is meant by hanging? ......

6.10 LET US SUM UP

Fresh fish is the most preferred form for the consumers. However making available fish in fresh condition to the consumers is not always possible due to logistic reasons. Hence we resort to preservation methods. Of these, the traditional preservation methods such as curing, sun drying, salting and smoking are very important and have played a great role in getting even valuable foreign exchange in earlier days. Even at present rural living masses in many countries resort to cure fish products in times of abundant catch. Cured fish also finds good market in certain section of people who live in rural areas and highlands. Smoked fish is even considered a delicacy in certain countries. These traditional methods are described in detail taking care to expose all the points. These traditional preservation methods have now given way to modern preservation techniques such as freezing, canning, pouching etc.

6.11 GLOSSARY

Alienating : Differentiating. Arrhenius : Rate of reaction related to temperature. Autoxidation : Fat oxidation in environment. Camouflage : A covering to misguide the presence. Carcinogens : Cancer producing. 38 Coagulate : Changing to a solid state. Dried, Cured and Smoked Products Cocci : Shape of bacteria – small rod. Dexterously : Skillfully handled. Disastrous : Causing great damage. Discolouration : Which has changed the colour. Emulsion : Creamy liquid. Eviscerated : After removal of internal organs. Fermented : Which has undergone chemical changes. Garcinia : A fruit with sour taste used as a condiment . Halophiles : Salt tolerant bacteria / microbe. Halophilic : Salt loving bacteria or microbe. Kilns : Furnace. Mesophilic : Microbe which grows at 30oC. Micro-aerophilic : Microbe requiring small quantity of air. Pyrolysis : Degradation or burning. Saturated : Concentrated. Shrinkage : Becoming smaller. Toughening : Making stronger. Volatile : That which changes to gas.

6.12 SUGGESTED FUTHER READING

Balachandaran, K. K. 2001. Post-harvest Technology of Fish and Fish Products. Daya Publishing House, New Delhi. Gopakumar, K. 2006. Text Book of Technology. Technical Editor, Indian Council of Agricultural Research, New Delhi. Hall, G. M. 1997. (Ed.) Fish Processing Technology, Blackie Academic and Professionals, London Zaitsev, V. et.al. 1969. Fish Curing and Processing. MIR Publishers, Moscow

6.13 REFERENCES

Gopakumar, K. 2006. Text Book of Fish Processing Technology. Technical Editor, Indian Council of Agricultural Research, New Delhi. Hall, G. M .1997. (Ed.) Fish Processing Technology, Blackie Academic and Professionals, London. Sen, D.P. 2005. Advances in Fish Processing Technology. Allied Publishers, New Delhi. Zaitsev, V. et.al.1969. Fish Curing and Processing. MIR Publishers, Moscow. 39 Fishery Products 6.14 ANSWERS TO CHECK YOUR PROGRESS

Check Your Progress 1 1) At present about 12-15% of marine fish landed is processed by traditional methods. 2) Sun drying, dry salting and mona curing, wet salting, pit curing, colombo curing and smoking and drying (Mas-meen). 3) Kench curing, pickling and brining. 4) Del Valle Nickerson method of salting Check Your Progress 2 1) The conditions of external ambient atmosphere such as its temperature, wet bulb depression, air velocity, direction of air-stream, shape and area of the surface determine the rate of drying. 2) A black surface absorbs the heat radiation of the sun in a most efficient way and thereby causes the temperature of such a surface to rise more compared to that of a surface with any other colour or shade. Thus, drying rate of a fish or a fish product would be more when dried on such a surface or with air heated with a black surface. 3) In a solar dryer, heat radiation from the sun is trapped by conduction process through the use of different simple devices such as blackened corrugated GI sheets which raise the temperature of air. 4) In the solar tent dryers solar radiation is allowed to pass through a clear surface which may be a transparent glass or polyethylene sheet and is absorbed by the black surface of the floor and the back of the dryer. Check Your Progress 3 1) Halophiles characterized by the production of intense red or pink pigments are known as red halophiles. 2) ‘‘Dun” shows up as small, brown, black or fawn coloured spots or tufts all over the surface of fish. These patches are in fact growth of halophilic or halo-tolerant moulds of Wallemia sebi (or Sporendonema epizoum). 3) Aspergillus spp., Penicillium spp., Acremonium spp., Wallemia sebi and Sporendonema epizoum Check Your Progress 4 1) Polyester polyethylene laminated pouches have been found to be highly suitable for hygienic retail packaging of cured fish products. 2) Preservation, nevertheless, is still the prime objective of fish smoking in most parts of the world. 3) Hard woods, such as oak, hickory, cherry, apple and beech, burn to give a smoke with the more phenols, which both preserve and give a characteristic, ‘medicated’ flavours to the product. 40 4) Colour imparted to the fish by the smoking process is due to carbonyl amino Dried, Cured and reactions of the Maillard type. Smoked Products 5) These are splitting and cleaning, salting and hanging. 6) In the process, fish is hung to drip either on racks or in the kiln.

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