Modified atmosphere packaging of freshwater fish

Abstract

A preservation method that could extend the shelflife of fresh, freshwater fish would be of nutritional and economic importance to a nation like Kenya, where 90% of all the fish landed comes from the freshwater environment, and where fresh fish is highly valued. In this study, modified atmosphere packaging of freshwater fish (Rainbow trout,salmo gairdneri) was investigated for its potential in extending the shelflife, in comparison to the traditional method, (ice storage) currently being used in Kenya. Fish stored in several gas compositions were investigated, (100% CO2, 60/40 % CO2/N2' 50/50 % CO2 /N2 ' and 50/50 % CO2/02) for the inhibitory effect on microorganisms, the effect on the quality as judged by a panel using the TFRU system, and by use of the GR Torrymeter. Each of the gas compositions used demonstrated an inhibitory effect on microorganisms with the microbial load of the skin samples remaining below 1Q4 Cfu/cm/ for 21 days. Maximum inhibition of the microbial flora was achieved by 100% CO2 atmosphere. There was a correlation between increasing CO2 level and inhibition of microflora. Lactic acid bacteria were not evident as part of the microbial population. Storage life was limited by organoleptic characteristics rather than microbial spoilage. There were changes in the CO2 level in the MAP pouches which correlated with pH changes in the flesh and drip loss.