Abstract:

After inoculation with Shewanella putrefaciens, a common fish spoilage bacterium, the sterile block and juice of large yellow croaker were stored at (5 ± 1) ℃, and the changes in sensory quality, total volatile base nitrogen (TVBN), trimethylamine (TMA) and bacterial count, the growth kinetic parameters of this species of bacteria and the yield factors of microbial metabolites (YTVBN/CFU and YTMA/CFU) in sterile fish block and juice during the storage were comparatively measured in order to evaluate the two methods of determining the spoilage ability of Shewanella putrefaciens. The post-inoculation shelf-lives of sterile fish block and juice were 162 h and 132 h, respectively, the TVBNs 32.16 mg/100 mL and 29.64 mg/100 mL, the TMAs 9.31 mg/100 mL and 0.99 mg/100 mL, the bacterial counts 8.67 lg(CFU/mL) and 8.56 lg(CFU/mL), the YTVBN/CFU values 2.58×10-10 mg TVBN/CFU and 1.98 × 10-10 mL TVBN/CFU, and the YTMA/CFU values 2.12 × 10-10 mg TMA/CFU and 1.27 × 10-11 mL TMA/CFU at the end of shelf-life. The reliable parameter indicating the spoilage of fish juice was TVBN rather than TMA. The relative error between the YTVBN/CF values of fish block and juice was 23.64%. Thus, sterile fish juice is a promising matrix for the reliable determination of bacterial spoilage ability.

Key words: spoilage bacteria, spoilage ability, determination method, sterile fish blocks, sterilized fish juice