Functional Properties of Fish Proteins
Unilever’s fish business is largely based on frozen fish products. For the consumer the principal attributes determining the quality of these products are the flavour and the texture. Fish proteins impact primarily on the sensory attributes relating to th
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Unilever's fish business is largely based on frozen fish products. For the consumer the principal attributes determining the quality of these products are the flavour and the texture. Fish proteins impact primarily on the sensory attributes relating to the texture of products. Fish fillet is composed of parallel muscle fibres arranged in blocks known as myotomes. The myotomes are separated by collagenous sheaths and form the flakes of the cooked fillet. The texture of fish is determined to a large extent by the myofibrillar proteins within the muscle fibres. The handling of fish, throughout the supply chain, impacts on the state of fish proteins and thereby influences the final textural quality. For frozen fish products, the freezing process, and storage in the frozen state are important determinants of product quality. For gadoid species in particular, significant deterioration in texture can occur during frozen storage. These changes, although not fully understood, involve aggregation of the myofibrillar proteins. A patented process for the use of ultra high-pressure to control some of the textural sensory attributes of cod during frozen storage is described.
7.1
Introduction
Unilever's fish business is largely based on frozen fish products, with products sold under well-known household brands in Europe and the Americas. For the consumer, the principle attributes determining the quality of frozen fish products are the flavour and the texture. Although the enzymes in fish may contribute to flavour changes that take place during frozen storage, the proteins impact primarily on the texture of fish products. This chapter briefly describes the proteins of fish muscle. The effects of freezing and frozen storage on fish muscle and the implications for fish texture are discussed. A patented technology involving the use of ultra high pressure to control some of the textural sensory attributes of cod during frozen storage is described.
7.2
Proteins of Fish Muscle
Figure 7.1 shows the hierarchical structure of fish. The fish fillet is divided into blocks of muscle known as myotomes which are separated by collagenous myocomata. On cooking the collagen of the myocomata is denatured and the myotomes may separate, forming the flakes of the cooked fish. The fish muscle fibres run between adjacent myocomata. Within the muscle fibres are the myofibrils, the contractile elements of the muscle. The myofibrils are made up of thick filaC. Alasalvar et al. (eds.), Seafoods — Quality, Technology and Nutraceutical Applications © Springer-Verlag Berlin Heidelberg 2002
74
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Myotome 1-2 em across; these are the visible flakes in cooked fish Myofibril: 1-21Jm
o
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Thick filaments: containing myosin
Fig. 7.1. The structural organisation of fish flllet
ments of myosin and
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