Effects of repeated freezing and thawing on myofibrillar protein and quality characteristics of marinated Enshi black pork

Repeated freeze–thaw is one of the main reasons for quality deterioration of frozen meat products. The study focused on the changes of endogenous fluorescence, secondary structure, microstructure, and water retention and distribution in marinated and unmarinated Enshi black pork after 10 freeze–thaw cycles. The results revealed that marinated treatment significantly reduced the thaw and centrifugal loss (P < 0.05), and increased endogenous fluorescence intensity of samples. During the entire freeze–thaw process, free water was undetectable in marinated group. After the first 4 cycles, α-helix percentage in marinated group was higher than that in control group. Scanning electron microscopy results suggested that there was no obvious increase in muscle fiber gap until 8 cycles in marinated group. Conclusively, moderate marination could slow down the deterioration of myofibrillar protein and pork quality, but it would be better to limit freeze–thaw cycles within 4 to maintain the quality of marinated Enshi black pork.