This project commenced in July 1987, with the cooperation of various sections of the fishing industry, including oyster growers and processors, salmonid farmers, and producers of value added products.
For each of the products investigated, the basic research method has been to determine the microbial status of the product in conjunction with sensory evaluation. In this way a knowledge of the microbial ecology of each product under different storage conditions is built up and related to the functional characteristics (appearance, odour, taste, etc.) that cause rejection of the product by the consumer.
Most fresh seafood products in chill storage deteriorate rapidly as a result of the growth of gram negative psychrotropic bacteria mainly Pseudomonas and Alteromonas (now Shewanella). These organisms produce putrid spoilage compounds such as sulphides, ammonia and some amines. Manipulation of the storage conditions (e.g. gaseous atmosphere) or formulation of the product (pH, water activity) may lead to replacement of the gram negative microbiota with gram positive bacteria. The latter organisms tend to grow less rapidly at chill temperatures and produce less obvious spoilage changes leading to a longer shelf life.