Postmortem biochemistry of marine animals - digestive enzymes and transglutaminases

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The fish industry is an important component of Canada's agri-food sector, and generates millions of dollars in revenue each year. However, fish stocks have been declining in recent years. This fact coupled with the seasonal nature of the seafood harvest and the high perishability of the raw material make it necessary to develop more effective procedures to reduce spoilage to ensure availability of the products for human consumption. The two main factors responsible for the rapid loss of fish quality are microbial activity and autolysis by endogenous enzymes. Thus far, fish spoilage by microorganisms has been well studied, while the contribution of autolysis to the spoilage phenomenon is less well studied. The proposed study will investigate novel approaches based on high pressure in combination with other barriers such as natural antioxidants and low temperature storage, as tools for preserving premium seafood quality. Seafood processing also generates high volumes of discards that are currently not put to high value uses. However, the discards are rich is useful biochemicals such as enzymes that may be recovered in pure forms for several commercial applications. The global market for enzymes is estimated at 1.3 billon dollars (US) per year, with a growth rate of 12-15% per year. There is a growing need to discover new sources of enzymes to meet the market demands, and fish processing discards represent an underutilized resource material with potential to fill this need. In the proposed studies, two groups of fish enzymes (fish lipases and transglutaminases) will be recovered and investigated in transesterification reactions to incorporate useful biomolecules (e.g., omega 3 polyunsaturated fatty acids) in human foods for health benefits; and for transforming oils from fish processing discards into biodiesel as alternative fuel to reduce the dependence on fossil fuel. Fish transglutaminases will also be prepared and used to modify biomolecules to make them more resistant to degradation, and thereby facilitate the development of novel biomaterials for food and non-food uses. Such use of transglutaminases will be more acceptable to consumers compared with the use of chemicals to achieve simalar modifications in food products.