Variation of Edible Quality and Microflora of Grass Carp Fillets with Sizing during Refrigerated Storage

To determine the quality changes and shelf life of grass carp fillets with sizing (GCFS), the aerobic bacterial count, microbial succession, water holding capacity (WHC), total volatile basic nitrogen (TVB-N), thiobarbituric acid reactive substances (TBARS), biogenic amines, ATP-related compounds and K value of GCFS were analyzed during storage at 4 ℃ and 10 ℃. Results showed that the aerobic bacterial count of GCFS stored at 4 ℃ and 10 ℃ approached or exceeded the limit on 7 d and 3 d, respectively, suggesting that low temperature significantly affects microbial amplification and microflora composition in GCFS, especially retarding the growth of Acinetobacter, Shewanella and Aeromonas. During storage, no significant difference (P>0.05) of WHC in samples was observed. The pH of GCFS reached the lowest level on 3 d, and the contents of TBARS, TVB-N and the specific biogenic amines (cadaverine, putrescine, histamine and tyramine) increased continuously. Furthermore, the changes in nucleotide degradation were greatly affected by storage temperature. The K value of GCFS exceeded the recommended limit value (60%) after 7 d of storage at 4 ℃ or 3 d of storage at 10 ℃, meaning that the samples entered the stale state. The results of sensory evaluation showed a negative correlation between the quality and storage time, with the phenomena of textural softening, flesh discoloration and fishy-smell aggravation in raw/cooked GCFS stored at 10 ℃ for 3 d and 4 ℃ for 5 d. Considering the results of various indicators and the pursuit of high edible quality, the suggested shelf life of GCFS at 4 ℃ and 10 ℃ was 3 d and 1 d, respectively.