Effects of packaging on microbiological, chemical and physical properties of farmed rainbow trout (Oncorhynchus mykiss) stored in refrigerator

The effect of packaging type on the shelf life of gutted farmed rainbow trout (Oncorhynchus mykiss) stored in refrigerator (3°C) was investigated. The fish was gutted and washed at room temperature. They were packed individually in polyethylene-polyamide bags in three experimental packaging: the presence of air, vacuum, and modified atmosphere (60% carbon dioxide, 10% oxygen and 30% nitrogen). The samples were stored in refrigerator up to 15 days and evaluated for the microbiological enumerations, chemical and physical analysis at days 0, 3, 6, 9, 12 and 15. The numbers of mesophilic, enterobacteria and lactic acid bacteria in the various treatments were not significantly different, during the storage. The number of psychrotrophic bacterium was not significantly different up to the 12th days of storage in all the experimental groups, whereas the bacterial count was significantly lower in the modified atmosphere packaging. Changes in the acid values and TBARS were not also significant in all the experimental groups during the storage. The amount of drip loss in all treatments increased with time. In the 12th and 15th days of storage, the loss was significantly higher in the vacuumed samples. In all treatments, the hardness value of meat was considerably decreased in the third day compared to the first day of storage. The present study revealed that if the rainbow trout properly washed and gutted in the hygienic conditions and stored at a suitable temperature, the shelf life was extended up to nine days without using any specific packaging. Furthermore, the packaging conditions used in this study did not improve the shelf life of the gutted farmed rainbow trout stored at 3ºC.