Coated Seafood: A new approach in value addition

— C. Dutta and K.C. Dora

Value addition is the most promising sector in food processing industry, especially in export oriented fish processing industry. In general value addition means “any additional activity that in one way or the other change the nature of a product thus adding to its value at the time of sale.” Value can be added to fish and fishery products depending on requirement of different markets. Several fish used for domestic consumption such as ribbon fish, seer fish, threadfin breams, mackerel and carps are now used for export. Globally, it is a transition period in consumer preference where cooked products have started replacing raw products.

There is a vast scope for increasing fish consumption in India by the development of convenience food or “ready to eat” and “ready to cook” products. Fish and fishery products in frozen condition can be marketed in urban centres, where these convenience foods would have a great demand. The need for diverting the low valued fish for human consumption and the necessity for diversification of fish and fishery products to value added products need special emphasis.

A large variety of value added and different types of seafood both for export and internal market based on shrimp, lobster, squid, cuttle fish, bivalves, certain species of fish and minced meat from low priced fishes have been identified. This article presents a brief description of coated seafood and edible films are given below.

Coated seafood

A food product coated with another food stuff helps to enhance the food product characteristics like flavour and texture. It also protects the natural juices of foods during freezing or reheating so as to maintain crisp on the outside and tender and juicy inside. Also, it acts as a moisture barrier by minimizing moisture losses during frozen storage or microwave reheating.

Basic types of coated seafoods

There are five general categories of coated seafood products like Precooked, Raw breaded, Battered (for fryer finishing), Battered (for oven finishing) and Sauced.

Formation of coated seafood product

The unit operations in developing coated seafood are: Portioning/forming, Predusting, Battering, Breading, Flash frying, Freezing, Packaging and Storage.

Portioning/forming: The fish stick is usually cut from fish blocks in a series of separate band saw operation. This whole process in now completed in line in a continuous operation using rotating knives. Temperature in this operation is generally maintained around 60C. The variety of portion size and shape has increased enormously from 25g fish stick upto 200g portion.

Predusting: Predust is very fine, dry, raw flour material that is sprinkled on the moist surface of the frozen seafood substrate before any coating is applied. Predusting improves adhesion of batter to frozen greasy food surface. The most commonly used predusts are wheat flour, gums and proteins. Flavouring and seasoning agents can also be incorporated during predusting.

Batters: Batters are classified into two types i.e one is adhesive and the other is tempura. The traditional adhesive batter is generally fluid consisting of flour and water into which the product is dipped before cooking and frying. It forms a strong bond in between product and coating. It is recommended that the proportion of batter and water is in the ratio of 1:2 and the main ingredients that constitute the batter are starch, salt, seasonings, gums, egg etc. Moreover it renders an opportunity to incorporate a leavening agent to favour expansion of the product at the time of frying. The most commonly used ingredients may be classified under five categories namely Polysaccharides (wheat flour, corn flour, rice flour, gums), Proteins (milk powder, egg albumin, cereal, and seed proteins), Fat /Hydrogenated oil, Seasonings (sugar, salt, spices) and Water. Sodium-bicarbonate and tartaric acid act as leavening agent to release CO2. Generally wheat flour is added at 40%, corn flour 30%, rice flour <5%, leavening agent <3% and gums <1%.

Tempura type batter, initially developed in Japan, is a puff type special batter. For preparing tempura batter, corn flour is needed. Tempura type batter forms a crisp uniform layer over the food. The rheological property of the batter is its viscosity. The pickup and quality of the adhering batter and the handling properties of the battered product are also affected by viscosity. The temperature is very much vital during reconstitution of batter dough in water. The ideal water temperature has been suggested to be between 10-150C.

Breading: Breading is a cereal based coating, often of breadcrumbs. Mesh size may be coarse, medium or fine. Coarse, dense crumbs may be acceptable when the food is overheated and non oily appearance is desired. Generally oil absorption and rate of heat transfer are higher in porous than in dense granules. The particle size of flour may vary: coarse (60-140 mesh size), medium (20-60 mesh size), too fine (4-6 mesh size).

Pre-frying: In the normal manufacturing process, pre-frying in oil is carried out followed by freezing the product and the purpose of prefrying is primarily to set the batter /bread coating on the fish portion. Flash- frying develops a characteristic crust and gives the product a fried oily appearance and taste. The normal frying temperature is between 180-200 0C and the frying time is 20-30 seconds.

Freezing: Fried fish portion for freezing is air cooled. It helps to cool down the temperature of the coating and at the same time allow the batter cooking to recover from the frying shock. Freezing is usually performed through spiral freezer and is completed when external temperature of the product is around -100C.

Packing: Packing of coated seafood should be done in thermoformed containers. The packaged products are usually stored at -100C or lower.

Variety of Coated seafoods

Shrimp products: Breaded shrimp can be prepared both from cultured shrimp as well as wild shrimps. Shrimp in different forms such as peeled and deveined, butterfly, round tail on cooked and peeled are used. Generally, after processing shrimps are dipped into batter mixture and then rolled on the bread crumbs and flash fried at 1800C for 20 seconds.

Squid rings: Cleaned squid tubes are cut in the shape of rings followed by cooking in boiling brine (3%) for 1-2 minutes and then cooled, breaded and battered. The battered rings are flash fried at 175-1800C for 20 seconds, cooled, packed and frozen.

Stuffed squid: Firstly squid tubes are cleaned and filled with a stuffing mixture that consists of cooked squid tentacles, potato, and fried onion spices. The stuffed squid are then battered, breaded and flash fried.

Stretched shrimp (Nobashi) Increasing the length of peeled and deveined shrimp and minimizing its curling by making parallel cuttings at the bottom and applying pressure using simple mechanical device is a new technique. Shrimp is washed in chilled water containing 5 ppm chlorine, beheaded, deveined using bamboo stick and peeled keeping the last segment and tail intact. The tail is then trimmed and the shrimp is stretched using a metallic stretcher after making 2-3 parallel cutting at the bottom side. Then they are packed in thermoformed trays under vacuum and frozen at - 400C.

Bivalves: Live mussel, clams, oysters can be depurated and the meat is shucked out through boiling. The shucked meat is blanched in brine, cooled, battered, breaded, flash fried and packed.

Fish fillet: Skinless and boneless fillets of fish are brined in dilute brine in order to improve appropriate taste and colour. After brining and draining the fillets are battered, breaded and flash fried for 30 seconds.

Fish mince based products

Fish finger: Fish finger can also be prepared from the skinless and boneless fish mince. Foaming machines are used for reshaping large sections of mince blocks and the slabs are cut into thin finger, which are battered and breaded. They are then flash fried.

Fish cutlet: Fish cutlets are prepared using cooked fish mince which is mixed with cooked potato, fried onion and spices. It is then formed into square shape weighing about 40 gm each. The formed cutlets are battered, breaded and flash fried.

Recent innovation in technology for preparation of coated seafood

  • Reduction of oil during frying: Now a days consumers prefer to eat less oily food. Generally coated product absorbs cooking oil during flash frying. In order to reduce oil absorption, a small amount of Hydro-colloids are used. The most commonly used hydro -colloids are methyl cellulose and hydroxypropyl methyl cellulose.
  • Elimination of frying: Here coated product is immersed in hot water (700C) instead of frying. After heating, the product is further heated in micro-oven, cooled, frozen, packaged for storage at a temperature of –180C or below.
  • Grilling and sauce coating: A grilled fish fillet having less fat and flavoured with sauce has been developed. In this process, the fillet is applied with olive oil and then shed to the cooking tray in a grill. This significantly reduces the fat content of the cooked fish. The use of a flavoured sauce over the grill- marked fish gave flavour to the product. The sauce generally is composed of water (40-60%), vegetable oil (10-50%), seasoning (5-25 %), and gum thickner ( 0.2-1%). Popular sauce flavours include lemon-pepper.

Edible films and coating from animal origin:

Edible coatings can potentially extend the shelf life and improve the quality of food systems by controlling mass transfer, moisture and oil diffusion, gas permeability (O2,CO2), and flavor and aroma losses. Coating formulations can be used to serve as adhesive for seasonings or to improve the appearance of foods. For example, edible coatings can be sprayed or dipped onto the surface of snack foods and crackers to serve as a foundation or adhesive for flavorings. Active compounds (antimicrobials, antioxidants, nutrients) can be added to food coatings for extending the shelf life, preserving the colour and improving the nutritional value of foods. Edible coatings also have the potential for maintaining the quality of foods after the packaging is opened by protecting it against moisture, oxygen uptake and aroma losses. The application of edible coatings to meat and fish products may be produced by dipping, spraying, casting, rolling, brushing, and foaming Coatings must have bamer properties with regard to water vapour, oxygen, carbon dioxide and lipid transfer, while maintaining good color, appearance, mechanical and rheological characteristics.

Edible films as a solid sheet can be applied between the food components or on the surface of the food system in order to inhibit moisture, oxygen, cozy aroma, and lipid migration. Edible films with adequate mechanical properties could conceivably also serve as edible packaging for selected foods. An edible film should be generally recognized as safe (GRAS) and used within any limitations specified by the Food and Drug Administration (FDA). Many edible films can be produced from food-grade materials, but many require solvents to become soluble. Ultimately, any material that is used for direct food contact will face regulatory scrutiny. In particular, biopolymers that act as carriers of additives intend to migrate to the food for preservative effects.

Very little work has been done on the sensory properties of myofibrillar protein films. However, in one of the studies myoliibrillar protein coating was applied to fish specimens and tested using a strength-deformation rheogram. It was found to affect the texture of the meat slightly by increasing the mechanical resistance when sliced. It was determined that the film should be reduced in strength for it to have acceptable sensory properties as an edible coating on fish surfaces. No studies have reported the effects of protein films on taste; however, there are sporadic reports which have indicated that the films had a slight fishy odour. The majority of the research on myofibrillar proteins has focused its attention on coating fish to reduce the oxidative effect. A driving force for further development of these films appears to be the proper utilization of the under utilized/trash fish.

Conclusion:
The under utilized fish can be suitably diverted for preparation of coated seafood which is a part of value addition in seafood sector. The upcoming aquaculture industry can depend on two parallel processes in value addition i.e. minced meat technology and development of coated seafood product. Edible films and coatings are promising systems for the improvement of quality, shelf life, safety and functionality of fish and food. They can be used as individual packaging materials, food coating materials, active ingredient carriers and to separate the compartments of heterogeneous ingredients within food. The efficiency and functional properties of edible film and coating materials are highly dependent on the inherent characteristics of film-forming materials, namely biopolymers (such as proteins, carbohydrates, and lipids), plasticizers and other additives.

 

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References

Cuq, B. (2002). Formation and properties of fish myofibrillar protein films coatings. In:Protein-Based Films and Coatings (A. Gennadios, ed.), pp. 213-232. CRC Press, Boca Raton, FL.
Donhowe, I. G. and Fennema, O. (1994). Edible films and coatings: characteristics, formation, definitions, and testing methods. In: Edible Coatings and Films to Improve Food Quality (J. M. Krochta, E. A. Baldwin and M. Nisperos-Carriedo, eds), Technomic Publishing, Lancaster, PA., pp. 1-24.
Druchta, J. and De Mulder Johnston, C. (1997). Edible films solve problems. Food Technol. 51, 61-74.
Krochta, J. M. (1997). Edible protein films and coatings. In: Food Proteins and Their Applications (S. Damodaran and A. Paraf, eds.), pp. 529-549. Marcel Dekker, New York, NY.
Krochta, J. M. and De Mulder-Johnston, C. (1997). Edible and biodegradable polymer films: challenges and opportunities. Food Technol. 51, 60-74.
Sasiela,R. J. (2000). Further Processed Seafood In Marine and Freshwater Product, Roy. E. Martin CRC press, pp.355
Venugopal, V. (2006). Coated Products. In: Seafood Processing: Adding Value through Quick freezing. CRC press, pp. 259-280.
 

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