Recent developments in fish processing and preservation

Item Type article

Authors Pillai, V.K.

Download date 26/09/2021 17:31:28

Link to Item http://hdl.handle.net/1834/32038 RECENT DEVELOPMENTS IN FISH PROCESSING AND PRESERVATION

V. K. PILLA! Central Institute of Fisheries Technology, Ernakula:n.

A review of the literature on fish enzymatic, oxidative and hydrolytic processing wm reveal that most of the changes. Several substances were tried in important developments have taken place experiments to combat the above spoilage during the last twenty years. Sustained agencies. These included penicillic acid, work by teams of scientists in different sulphur drugs, streptomycin, tetracycline parts of the world has not only contributed compounds like CTC, OTC etc. The much to our knowledge of the chemistry immense possibilities of CTC as a fresh and technology of fish but also resulted in fish preservative was established beyond revolutionary changes in the methods of doubt (Boyd, et. a/. 1953). Low con­ preservation and processing of fishery centrations were found to enhance the products. shelf-life of iced fish by considerably long periods. This prompted large scale The primary aim of research in the trials and research in many countries on a field of fish preservation was to maintain variety of commercially important fish and fresh fish quality during storage for long shell fish. The informations collected on periods. Th~ real breakthrough in this the subject are enormous and are of much field took place with the finding that vaiue to the fish processing industry. The sodium nitrite is very effective in prolong~ initial fears of danger through oral intake ing the shelf life of fish (Tarr, 1941). It of CTC to public health have been dis­ was however soon realised that this counted and most of the major fish produ­ compound although effective in arresting cing countries have now legalised the use oxidative changes in fresh fish to some of this antibiotic in fresh fish preservation. extent, was not the ideal preservative. In India too a good deal of work has been Inspite of this the use of nitrites has been done on this subject. There are indications practised on a large scale in countries like that use of this antibiotic may turn out to Canada and Norway. be beneficial to the prawn processing industry in certain specific fields like pre­ The search for a complete preservative process preservation and long distance continued and in this the scientists had to transport of raw materials. deal with all the different types of spoilage occuring in fish, namely microbiological, CTC, althoug outstanding in its

90 performance, however has not provided micro- organisms in fish is worth the complete answer to the problem of fish investigating. preservation. The success of CTC treat· ment has been found to depend on various Work on the esters of p-hydro~ factors such as the freshness of the raw xybenzoic acid as anti-bacterial agents has material, the type of fish used, the extent been encouraging. Methyl through Octyl of initial bacterial contamination, conta­ esters have been found to exhibit pro­ mination with metal surfaces, possibility of nounced preserving activity potential. degradation products from fish to combine Lower chain length members are very with the CTC thus nullifying its effect etc. effective against gram negative organisms It is effective only against certain types of while increase in the alkyl chain length is micro-organisms (mainly gram negative marked by increase in their activity towards types) while the other organisms and the gram positive organisms. enzymes continue their action unabated. The specificity of the antibiotic to gram Extracts from natural vegetable negative organisms also brings in the material have been found to possess very additional question of certain species good antioxidant properties. Hot water predominating in the product and creating extracts from onion tops, green pepper an imbalance of the natural flora of the seeds, potato peels etc. are found to material, which may or may not have ill contain antioxidant properties in foods effects. having fat and water. The activity has been traced to flavonoides and related In recent years there have been compounds present in these extracts. renewed efforts to find out better preserva~ tive materials for fishery products. A new Vitamin K 5 , which has shown indica­ product called Myverol is undergoing tions as a preservative, increases the extensive tests as a preservative. The sensitivity of a number of bacterial strains antibiotic Tylosin lactate at 2.3 ppm to irradiation. This will permit radiation has been found to prevent growth of sterilization to be accomplished at lower anaerobic bateria for over one year (Anon, levels. This incidentally brings us to the 1963). Effectiveness of the antibiotic on recent developments in pasteurization and low acid, thermophilic and fiat sour radiation sterilization techniques for organisms have already been investigated. the preservation of fishery products. The enzyme is a fermentation product of streptomyces. It has a lactone ring stru­ Experiments carried out on shell fish cture with a molecular weight of approxi­ like lobster and crabs have shown that mately 900. Almost complete inhibitory normal pasteurization procedures will be effect on gram positive organisms has been very effective in arresting deteriorative found. It also appears that the antibiotic changes in these materials during long is specific in inhibiting the vegetative cells storage. Heat treatment at 70 to 75°C for of the causative agent for botulinum periods not exceeding 15 minutes either at intoxication. Studies with this enzyme a stretch or at intervals followed by have shown that no strain of spore formers immediate chilling and storage has been could withstand a concentration more than found to preserve the original t1avour of 4 ppm. The possibility of using this the material for a longer period. The compound in conjunction with ere, which technique however has not g:.tined much is specific only to gram negative organisms, attention so far although it offers the as an effective inhibitor against all types of possibility of further evalu:ttion. As

91 against this the technique of radiation is hoped that time and continued efforts pasteurization has evinced the interest of will provide these vital informations. fish technologists to a greater extent in the last few years. Attempts carried out in In the field of canning the conve­ many countries show the great potentiali­ ntional batch type thermal processes using ties of this technique. At an irradiation still or agitating retorts are giving place to level of 0.2 megarad using a Cobalt-60 more efficient methods. Continuous irradiator it has been possible to increase methods involving rotary cookers, hydro­ the shelf life of king crab meat to fourfold matic cookers, hot air sterilizer systems at a storage temperature of 0°C. Raw of Sweedish origin, gas flame heating shrimp irradiated at 0.5 to 0. 75 megarads process of French origin or HTST (high with 5 ppm CTC added kept well for temperature short time) process are gaining over 10 weeks at a temperature a little ground, atleast for the mere reason that over 0°C. The technique has however the sterilization time is much shortened. been found to have several disadvantages The HTST process is the shortest of all particularly \Vhen applied to fish foods these proces~es. The rotary cooker has ·having high fat content. Deep penetration fouud much favour in recent years with radiation split up the moisture into the industry as sterilization is over in three oxygen and hydrogen. These nascent gases to four minutes. exhibit very high oxidising and reducing properties. Their action starts a series of Another process that is fast gaining changes to the fat and other components ground is the Fluidized Bed Processing of the fish resulting in undesirable changes Method (Pigott, 1963). This process uses in flavour and odour of the material. a heated bed of fluidized solids for sterili~ zation purpose. The heated particles quickly transfer heat to the cans. Inert The most important development in solid particles of 50 to 120 mesh range like the field of fish processing is the discovery sand can be used. of the now well known 'Accelerated Freeze Drying' technique. This technique In the field of freezing of fish recent promises to become a major food proces­ studies have shown that frozen fish keep sing method. It provides savings to the better after an initial immersion in a consumers without compromising quality. solution of phosphate salts. Gels formed Both pilot scale and batch type Plants from sodium chloride and dextrose and have already been put in the market for from sodium alginate in presence of salt8 commercial use; and the present attempts of sodium and calcium are also being are to design continuous type accelerated used extensively in freezing operations. freeze drying Plants. Side by side with the Alginate jelly has been found extremely development of machinery for this process useful in reducing drip, preventing ranci­ research is also being continued with dity of fat and· other deteriorative changes. vigour both in India and in foreign Organoleptic evaluation of fish and prawn countries to find out the suitability of the coated with alginate jelly has indicated process to different varieties of fish that the fresh fish characteristics are products, the reconstitution properties retained during freezing and storage for of the processed material and its long periods. quality vis-a-vis the quality of the original raw material. Answers to many One of the recent developments in the of these are yet to be found. However it fish freezing industry is the application of

92 the principle of fast blast at -45.5°C. This out, which means development of newer is found not only to accelerate freezing products capable of meeting the demands (freezing takes place in 15 seconds) but of the consumers. Consumer type packs also seals the flavour and prevents of individually frozen prawn in aluminium moisture losses completely. The air lined polythene bags, boila ble plastic bags, velocity is such that it literally offsets more breaded prawn products etc. are becoming than nine tenths of the weight of the increasingly popular in the Western material making it float through the freez­ countries. Considering the potentialities ing tunnel so that cooling is uniform on of our prawn processing industry H is only all the sides of the block. Still more recent justifiable that we start work on these lines is the use of liquid nitrogen in freezing without delay. We have also to find (Kurzinski, 1965) and refrigeration of immediate solution to important problems fresh and frozen perishable goods includ­ like discolouration in dried prawn pulp, ing fishery products in transit. This new belly bursting in ice stored and frozen system has demonstrated several advanta­ sardines etc. Of course it has to be ges including operating efficiency over remembered that a great deal of basic mechanical refrigeration systems although research is needed before perfecting a it is considered somewhat more expensive technique, developing a new product or than the conventional freezing rrocesses. solving a technological problem. It is Portable Polarstream refrigeration units gratifying to note that most of these are are now available for use in trucks. With being tackled by the Central Institute of the availability of liquid nitrogen at Fisheries Technology with encouraging cheaper rates this process may turn out to results. be successful and competitive even in India where internal distribution of fish is yet to REFERENCES : develop. Anon, 1963. Canner & Packer, 132, 7, The foregoing is only an outline of 25-66. the major developments that have taken Boyd, J. W., Brumwell, C and Tarr, place in the fish preservation and proces­ H. L.A. 1953. Fish Res. Bd. Canada sing fields. Many of these can profitably I Prog. Reports Pac. Coast Stns., be applied to the prawn processing No. 96, 25. industry. Competition in the world market for the conventional types of frozen Kurzinski E.F; 1965. Cryogeric Engineering News, 57, Aug-Sept. and canned products is on the increase and only top quality at lesser price will be able Pigott, G. M; 1966. Food Processing to sustain the industry. Better avenues of 24, 1, 79. utilizing the product will have to be found Tarr, H. L. A; 1941. Nature 147, 417.

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