Research on quality changes and indicators of Pandalus borealis stored under different cooling conditions

The quality changes of Northern shrimp, Pandalus borealis, stored in ice, liquid-ice or salt-water mixed with ice, either at ambient temperature of -1.5 or 1.5℃, were evaluated by using sensory assessment, physical methods, chemical and microbial analysis. Storage in liquid ice was more effective than ice or salt-water mixed with ice, in delaying spoilage of the shrimp. It was observed that the total volatile nitrogen (TVB-N) content decreased during the first day in shrimp stored in liquid ice at both -1.5°C and 1.5°C and its formation was further delayed for 3 days in shrimp stored at -1.5°C. In other groups the TVB-N content increased with time. The trimethylamine (TMA) value increased gradually with storage time, in all samples, except for the one stored in liquid ice at -1.5℃ during the first day of storage. Total viable counts (TVC) showed that bacteria grew most quickly in shrimp stored in ice and in salt-water ice, followed by those in liquid ice at 1.5℃ or -1.5℃ respectively throughout the storage period. Lowest counts were observed in sample stored in liquid ice at -1.5℃ where the lag phase of growth of bacteria was apparently extended at the beginning of storage. Principal component analysis (PCA) and analysis of variance (ANOVA) were performed to analyse the variation and correlation of indicators. The results show good correlation between some of the quality indicators, TVB-N, TMA, TVC, pH, NH_3 response of electronic nose and sensory evaluation.