Search

Summary: The effects of hydrostatic thawing (HT), flowing water thawing (FT), ultrasonic thawing (UT), microwave thawing (MT), and microwave‐combined ultrasonic thawing (MUT) on the quality of yellowtail fillets were investigated via thawing time, physicochemical quality, water retention, microstructure and water migration distribution. The results showed that MUT had a shorter thawing time, second only to microwave thawing (MT) and significantly shorter than other thawing methods. Moreover, MUT could retain a better performance of the samples, such as colour, texture, water retention and moisture distribution, and prevent damage to the microstructure. In addition, freshness analysis showed that pH, total volatile saline nitrogen and K values were optimal for MUT. Therefore, MUT could be a viable thawing method that increases the thawing rate of yellowtail fillets while maintaining their quality characteristics. [ABSTRACT FROM AUTHOR]

The effects of ultrasonic power (0, 150, 300, 450, and 600 W) on the extraction yield and the structure and rheological properties of pepsin-soluble collagen (PSC) from albacore skin were investigated. Compared with the conventional pepsin extraction method, ultrasonic treatment (UPSC) significantly increased the extraction yield of collagen from albacore skin, with a maximum increase of 8.56%. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that peptides of low molecular weight were produced when the ultrasonic power exceeded 300 W. Meanwhile, secondary structure, tertiary structure, and X-ray diffraction analyses showed that the original triple helix structure of collagen was intact after the ultrasonic treatment. The collagen solutions extracted under different ultrasonic powers had significant effects on the dynamic frequency sweep, but a steady shear test suggested that the collagen extracted at 150 W had the best viscosity. These results indicate that an ultrasonic power between 150 and 300 W can improve not only the extraction yield of natural collagen, but also the rheological properties of the collagen solution without compromising the triple helix structure. [ABSTRACT FROM AUTHOR]

BACKGROUND: Frozen tilapia fillet has become a leading aquatic product. High drip loss, dry and fibrous mouthfeel, and an unappealing appearance are its main problems. It was hypothesized that light salting could improve the quality, and that the preparation conditions would affect the storage stability of frozen tilapia fillets. RESULTS: The quality changes of lightly salted tilapia fillets were evaluated during frozen storage, and the underlying mechanisms were studied from the physicochemicaland microstructural perspectives. Though the salt content was 1.5% in all samples,the amount of ice crystals in frozen tissues decreased with the descending water content and freezing point (P < 0.05). No intracellular voids were observed in the samples prepared under proper salting conditions, and the myofibers were plump and smooth after freezing‐thawing, which contributed to the high water‐holding capacity of lightly salted fillets. After 28 days,the water‐binding capacity of the salted groups was 14.69%−18.62% higher than that of their unsalted counterparts (P < 0.05). The reduced protein solubility in the salted fillets was likely to have occurred because the solubilized and unfolded proteins interacted more easily during frozen storage. The oxidation degree of myofibrillar proteins was also affected by salting condition, and the fillets with less oxidized sulfhydryl groups maintained high springiness after 28 days of frozen storage. CONCLUSION: The salting condition of 9% NaCl solution for 1 h was recommended for the preparation of lightly salted fillets from freshwater fish, taking into account quality, processing efficiency, and storage stability. The enhanced water‐holding capacity and texture of lightly salted tilapia fillets were attributed to modified physicochemical and microstructural properties. These results could provide a scientific basis for the processing and storage of high‐quality, frozen, lightly salted fillets from freshwater fish. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]