Evaluation of a predictive model for the shelf life of cod (Gadus morhua) fillets stored in two different atmospheres at varying temperatures.

The shelf life of fish and food in general is difficult to predict especially if stored at varying temperatures. Shelf life models were constructed (Einarsson, 1992) for cod fillets stored at constant temperatures. The aim of this study was to evaluate if these models could be used to predict spoilage and bacterial growth in cod fillets stored in air and modified atmosphere at constant and varying temperatures. Fresh fillets were packed and stored at constant or varying temperatures between -2 degrees C and 5 degrees C. Samples were taken at regular intervals for bacteriological and sensory evaluation. The results showed that fish stored at +0.6 degrees C in air had a shelf life (assessed by sensory analysis) of 11 days which is close to what could be expected and predicted. The increase in bacterial number observed was generally less than predicted. For fish fillets, stored in air at +5 degrees C for 3 days, then at +0.6 degrees C for 3 days and finally at -2 degrees C, the shelf life was found to be 7 days which was in good agreement with the predicted shelf life. The shelf life of fillets stored at same the temperatures in modified atmosphere was found to be 9 days but by prediction 11 to 12 days. The models for predicting changes in sensory score were more accurate than those predicting changes in bacterial numbers.