Changes in Muscle Quality and Microbial Community Structure of Eel Slices during Cold Storage
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Abstract:
The changes in muscle quality and microbial community structure of eel (Asian swamp eel, Monopterus albus) slices during 7 days of cold storage at 4 ℃ were assessed by measuring physicochemical indexes, such as color difference, microstructure, pH value, total volatile base nitrogen (TVB-N), and total viable count (TVC), as well as flavor-related substances, such as volatile compounds and free amino acids. Furthermore, associations of bacterial genera with characteristic chemical indexes, color difference indexes, and key amino acids were examined. The results showed, that with the prolongation of cold storage, the color of eel slices gradually became yellow and finally turned brown, and the muscle cell gap, TVB-N content, TVC, and H* value all gradually increased, whereas the R630/580 ratio and the levels of essential amino acids gradually decreased. Specifically, the pH value diminished from 7.02 to 6.19 on day 1 (P<0.05), while the TVC and TVB-N contents exceeded the corresponding limits on days 3 and 7, respectively. The response of eel slices to the sensor W5S was the highest during the cold storage period. After day 3, the odors of the eel slices changed considerably, and the leucine contents decreased. The microbial diversity of eel slices gradually decreased during cold storage, and the dominant genera were Macrococcus and Acinetobacter in the early cold storage period (first three days) and Brochothrix, Pseudomonas, and Carnobacterium after day 3. The results of correlation analysis showed that R630/580, H*, pH, TVC, and TVB-N values as well as the serine, glycine, and leucine contents significantly correlated with the microbial community structure during cold storage; furthermore, microbial growth was the main reason for the changes in freshness, color, and flavor of eel slices during cold storage. This study provides a theoretical basis for cold processing of Asian swamp eels.
