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Chapter 1.2.2
Module:  1.
Downstream processing methods of aquaculture and fisheries side stream biomass to produce targeted nutritional supplements
Unit:  1.2.
Fish proteins and protein hydrolysates - products and applications
Chapter:  1.2.2.
Fresh fish side stream products and applications

Fish mince

Minced fish is a comminute flesh produced by separation from skin and bones. Separation is a mechanical process (for producing minced fish) whereby the skin and bones are removed from the flesh. Bone separators working on different principles are available commercially, but the separator most widely used for fish is of comparatively simple design. The total yield of flesh of low bone content is higher than with filleting alone; up to twice as much can be recovered by separating flesh directly from headless gutted fish. When the fish is first filleted, an additional 8-12 % flesh can be separated from the filleting waste. Some people do not like fatty fish such as herring and mackerel partly because of the large numbers of small bones remaining in the fillets. Mince made from these fishes is almost free from bones and might therefore be more widely acceptable. Flesh from underexploited species, such as blue whiting, that are difficult to fillet efficiently (small size or awkward shape) can readily be removed in a bone separator. Mincing can increase the risk of oxidation due to membrane disruption, contact with metals and air. Mince spoils faster than fillets, mainly because the structure of the flesh is degraded during separation, and extra care must be taken to maintain good quality. Minced fish is also more easily denatured during freezing. Thus, fish used for making mince must be of very high initial quality, and processing has to be completed quickly, with emphasis on hygiene and low temperature.

Restructured fishery products

Restructured fishery products are products made from minced and/or chopped muscle and which are used, with or without ingredients, to make other products with a new appearance and texture (more). For some time, there have been products in the form of fingers or other shapes intended basically for children's foods, which are covered in breadcrumbs or batter then frozen for use as fried products. Also, recent years have seen the development of a new generation of fishery products called analogues or substitutes, most of which mimic seafood or other high-value products. Such products are made essentially from surimi, which is ground, thoroughly washed and refined fish muscle. The reason for restructuring fish muscle is that the supply of high-quality fishery products is limited, and many are becoming exhausted because of severe overfishing. There are therefore not many options that do not entail the utilization of species that have not traditionally been commercialized either very much or at all. One of the chief advantages of restructured products is that the composition of the end-product can be modified by reformulation of the original product once this has been chopped or ground. In this sense, the process might be said to be one of eliminating some constituents or adding other new ingredients or additives. These ingredients or additives may be categorized as (a) favouring storage, (b) functional from a technological standpoint and (c) functional from a nutraceutical standpoint. There are several types of ingredients that perform more than one of these functions.

Fish burgers

A general protocol of preparing a given product once ingredients in the formulation are decided is as follows: Fish is headed, gutted, and viscera removed. Gutted fish is filleted mechanically or with knives. Fish fillets are first chilled at 2℃ usually for 2-3 hours, and then frozen for up to four weeks depending on the constraints of the industrial process. One of the outcomes of this treatment is to harden the flesh, which improves the structural properties of fish meat in the final product. Following storage, fillets are minced using crushing and fine cutting with various choppers to yield homogenised mince. Preparations are made by blending appropriate amounts of fish meat with starch, non-starchy hydrocolloids, vegetables, dry fruit leathers, condiments, sucrose, etc. The homogenous mixture is stuffed in manually / automatically operated machines for pressing thus producing firm and free from air burgers of variable weight, height, and diameter. End products are stored under conditions of domestic freezing (about −20℃), preferably using bulk vacuum packaging, for quality control analysis (microbial growth, chemical composition, colour, etc.), and retailing. Fish burger, being a convenience food prepared out of comminute fish, spices, and starch, is an important delicacy in fast food trades and home preparations. Frying of fish burgers imparts an aromatic, savoury flavour to the traditional fish burgers and they are popular in mild heated lunch or dinner meals or simply eaten without heat treatment as a ready-to-eat (RTE) product. Different minced fish products from a variety of fish species are presented in Table 1.2.2.

Minced fish burgers of improved eating quality

In the development of processed fish products, it has often been used minced or filleted fish with additives, e.g., polyphosphates, which reduce drip loss especially in products made from thawed frozen fish. Spices can be added to improve taste according to market requirements. Fish muscle protein does not possess sufficient functionality to hold together a cohesive processed product, therefore are often corn flour or corn starch introduced to enhance the structure and cohesion of products made increasingly from a mixture of prime and inferior cuts of minced fish. Changing consumer expectations, with amplified focus over what people are eating is placing pressure on clean label products, using less additives in the products. People associate a diet with lifestyle choices and increasing personalization represent a continuation of this trend. High concentration of proteins is also requested as a healthy product for many consumer groups, e.g. for elderly people, patient groups and sports enthusiasts.

Table 1.2.2 Minced fish products (burgers) with different types of fish
Topic Fish type Reference
Freshwater Fish Burgers Carp, Goldfish, Perch and Tench (Branciari et al. 2017)
MA packaging of burgers Sea bass (Dicentrarchus labrax) (Danza et al. 2017)
Instrumental and sensory properties Many types - fish burgers (Kasapis 2009)
Transglutaminase on quality and gel properties Silver carp (Li et al. 2017)
Tuna Protein Isolates for Better Sensory Quality and Frozen Storage Stability Silver carp (Shaviklo et al. 2016)
Fish burger Catla (Catla catla) Fresh water fish (Vanitha et al. 2015)
Effects of Natural Extracts on the Quality Changes of Frozen Chub Burgers Mackerel (Scomber japonicus) (Ozogul & Ucar 2013)
Chemical, physical and sensory properties - various types of flour Farmed Gilthead Sea Bream (Sparus aurata) (Makri 2012)
The effect of mincing method on the quality of refrigerated whiting burgers Whiting (M. merlangus, L. 1758) (Kose et al. 2009)
Storage properties of refrigerated whiting mince after mincing by three different methods Whiting (M. merlangus euxinus, N. 1840) (Kose et al. 2006)