Myofibril degradation and structural changes in myofibrillar proteins of porcine longissimus muscles during frozen storage

The effect of frozen time and the temperature on myofibril degradation and the structure of myofibrillar proteins of porcine longissimus muscles were investigated. With extended frozen time and increased temperature, the muscle fibres became broken; the muscle cells became irregularly arranged; and the fragmentation index value, number of ionic bonds, and number of hydrogen bonds of the samples significantly decreased. Meanwhile, the myofibril fragmentation index value, number of hydrophobic interactions, and number of disulphide bonds significantly increased (P < 0.05). After 12 months of storage, the intensities of I760/I1003, I850/I830, I1450/I1003, and I2945/I1003 in the samples frozen at -8 °C were reduced by 4.36 %, 1.28 %, 1.86 %, and 0.74 %, respectively. A reduction in the maximum absorption peak and a red shift were observed in the ultraviolet spectrum. Therefore, frozen storage resulted in significant damage to the tissue microstructureand caused accelerated protein degradation, and the loss of protein structural integrity.

Quality changes and indicator proteins of Litopenaeus vannamei based on label-free proteomics analysis during partial freezing storage

Litopenaeus vannamei are known to deteriorate in quality during low-temperature storage. This study demonstrated the potential protein indicators of partial freezing of stored shrimp by traditional quality parameters and label-free based proteomic techniques. The carbonyl content and myofibril fragmentation index (MFI) of shrimp increased from 0.56 ± 0.03 to 2.14 ± 0.03 nmol/mg and 13.09 ± 0.14 to 54.93 ± 0.96, respectively. Within the extension of storage, the trichloroacetic acid (TCA), cooking loss and whiteness significantly increased. A total of 240 proteins changed in abundance at 10, 20, and 30 days compared to fresh samples. Projectin, ribosomal protein and histone were potential biomarkers for protein denaturation and oxidation in shrimp muscle. Myosin heavy chain and glyceraldehyde-3-phosphate dehydrogenase corresponded with the degradation of muscle proteins. Myosin light chain, tubulin alpha chain, and heat shock protein correlated with tenderness and water holding capacity; meantime, malate dehydrogenase and hemocyanin can serve as color indicators. Further study of the properties of these indicator proteins can inform their exploitation as quality indicator proteins during partial freezing storage.

Effects of Sous Vide Cooking on the Physicochemical and Volatile Flavor Properties of Half-Shell Scallop (Chlamys farreri) during Chilled Storage

This study explored the effects of sous vide (SV) cooking treatments on the physicochemical quality and volatile flavor of half-shell scallop (Chlamys farreri) during 30 d of chilled storage. The vacuum-packed scallop samples were cooked at 70 °C (SV-70) and 75 °C (SV-75) and maintained for 30 min. The samples were compared with the positive control (cooked at 100 °C for 10 min, CK). The results indicate that the total volatile basic nitrogen (TVBN), pH, texture, and malondialdehyde (MDA) content gradually increased, while the myofibrillar protein (MP) extraction rate of the CK, SV-70, and SV-75 samples significantly decreased with increasing chilled storage time. Significantly, the SV cooking treatments maintained a much higher water-holding capacity of scallop muscle, compared with the conventional cooking process at 100 °C. Additionally, the SV-75 cooking treatment maintained relatively stable TVBN, pH, and MDA content, springiness, and shearing force properties of scallop samples, especially during 0-20 d of storage. Volatile flavor analysis showed that a total of 42 volatile organic compounds (VOCs) were detected in the scallop samples, and there were no considerable differences in these VOCs between the CK and SV-75 cooked samples (0 d). Overall, the SV cooking treatments effectively maintained acceptable and stable physicochemical and volatile flavor properties of half-shell scallop samples during chilled storage.