Effects of modified atmosphere packaging on the shelf life of gutted rainbow trout (Oncorynchus mykiss) stored at 3 °C

摘要

The objective of this study was to find out the effect of modified atmosphere packaging on the shelf life of gutted rainbow trout and to determine the optimum composition of gas mixtures. Microbiological analysis, thiobarbituric acid reactive substance (TBARS), hardness values (maximum force of puncture test) and drip loss were determined in gutted rainbow trout stored at 3 ± 0.5 °C under 5 different atmospheric conditions; T_1: 60% CO_2+40% N_2, T_2: 40% CO_2 +10% O_2+50% N_2, T_3: 60% CO_2+10% O_2+30% N_2, T_4: vacuum-packaged and T_5: air-packaged. Mesophilic, psychrotrophic and enterobacteriacae counts increased throughout the storage time and there were no significant differences among the groups. Counts of lactic acid bacteria (LAB) at the 0th day were about 1.4- 1.6 log Cfu/g which rose to 4.4-7.5 following fifteen days of storage. The highest and lowest LAB counts were belonged to the T1 and T_2 groups, respectively. TBARS increased after 15 days of storage with the highest level for T_1 and T_2 compared to others experimental groups. Hardness values were also significantly decreased during 72 hours of storage, although the values were similar among all the groups. The highest drip loss was recorded in the T_4, which was succeeded by the T_1 and the lowest exudates was additionally found in the T_3. Results of the current study revealed that mixture of 60% CO_2+30% N_2+10% O_2 provided an appropriate atmospheric condition to elongate the shelf life of gutted rainbow trout which was still acceptable after 12 days of storage at 3 °C.