Retort Pouch Processing of Fish Sausage

Abstract- A study was undertaken on thermal processing of fish sausage packed in retort pouch to assess quality variations during storage. Meat of Japanese threadfin bream (Nemipterus japonicas) was used. Three lots of raw fish paste stuffed in cellulose casing of 1.5 cm diameter were preheated in water bath at 88-90 ̊ C for 0, 10 and 60 min. they were further packed in polyester- aluminium foil- polypropylene laminate retort pouch under vacuum and thermal processed in retort at 110 ̊ C for 30 min. products that were not preheated were accepted most as per sensory analysis based on the parameters odour, taste, texture and overall accaptablility.

Six lots of the products packed in retort pouches were then subjected to retorting at a process temperature of 110 ̊ C for different periods in order attain F0 values of 3.6, 4.4, 5.4, 6.2, 7.2 and 8.2. Based on various tests, viz. hardness, resiliency, pH, total plate count (TPC), total fungal count (TFC) and sensory evaluation, two F0 values were selected for storage study, viz. F0 5.4 and F0 8.2. products processed to either of the F0 value were stored at two temperatures, room temperature (25-32 ̊ C) and chilled at 2 ̊ C for a period of 32 days.

Hardness and resiliency showed a gradual decrease during storage of all four combinations of the product whereas pH, peroxide value and total volatile base nitrogen content increased slightly. Comparatively the rate of change in the values of all parameters was highest in product processed at F0 5.4 and stored at room temperature, and was lowest in that processed at F0 8.2 and chill stored. In the case of the other two combinations, viz. F0 5.4 and chill stored and F0 8.2 and stored at room temperature, rate of change was in between those of the former two. TPC and TFC were absent throughout the storage period in both the lots processed to F0 8.2. In the lots processed to F0 5.4, TFC was again nil, but TPC increased by over one log cycle, with the lot stored at room temperature showing higher counts. Sensory quality of the products were all initially judged high, but during storage there was a steady decrease in the scores of all the parameters in all the products. However, product processed at F0 5.4 and stored at room temperature showed greater rate of decrease and that processed at F0 8.2 and chill stored showed lowest rate.

It was concluded that retort pouch processing of fish sausage to an F0 value of 8.2 and storing in chilled condition would be most ideal, but it would be more convenient to store the same product at room temperature although the rate of quality loss can be slightly more.