Effect of ultrasound combined with pineapple protease treatment on the tenderness of dried shrimp.

BACKGROUND: In order to improve the tenderness of dried shrimp products as well as to reduce the hardness of the meat during the drying process, shrimp were treated with ultrasound combined with pineapple protease and the tenderization condition was optimized by measuring the texture and shear force of dried shrimp. In addition, the sulfhydryl content, myofibril fragmentation index (MFI) and microstructure were also examined to clarify the mechanisms of shrimp tenderization. RESULTS: The results showed UB1 group with ultrasonic power of 100 W, heating temperature of 50 °C and pineapple protease concentration of 20 U mL-1 were the optimum tenderization conditions, where shrimp showed the lowest hardness (490.76 g) and shear force (2006.35 gf). Microstructure as well as sodium dodecyl sulfate-polyacrylamide gel electrophoresis results suggested that during the tenderization process the muscle segments of shrimps were broken, degradation of myofibrillar proteins occurred, and MFI values and total sulfhydryl content increased significantly (P < 0.05) (MFI value = 193.6 and total sulfhydryl content = 93.93 mmol mg-1 protein for UB 1 group). CONCLUSION: Ultrasound combined with bromelain could be used as a simple and effective tenderization method for the production of tender dried shrimp. The best conditions were 100 W ultrasonic power, 50 °C ultrasonic temperature, and 20 U mL-1 bromelain. © 2024 Society of Chemical Industry.

Comparison of freezing and heating treatment sequence on biochemical properties and flavor of swimming crabs (Portunus Trituberculatus) meat during freeze-thaw cycles.

The objective of this study was to compare the effect of freezing and heating treatment sequences on the biochemical properties and flavor of crab (Portunus trituberculatus) meat during freeze-thaw cycles. The results showed that pH, color, K and microstructure changes in the H-F group were not significant with increasing number of freeze-thaw cycles, but TVB-N values increased and WHC values decreased. However, with the increase in the number of freeze-thaw cycles, pH and WHC significantly decreased and TVB-N, L* and K values significantly increased in the C and F-H groups. Proteins were degraded in all groups, but the lower degree of degradation occurred in the H-F group. Although the total free amino acid content decreased with increasing number of freeze-thaw cycles in each group, the high content of AMP and IMP in the H-F group suggested that it still had a better flavor.

A pH-indicating intelligent packaging composed of chitosan-purple potato extractions strength by surface-deacetylated chitin nanofibers.

The goal of the study is to develop a novel pH-indicating intelligent packaging by using purple potato extractions (PPE), chitosan and surface-deacetylated chitin nanofibers (CN). Since the major pH-sensitive pigment of PPE was anthocyanin (24.3 mg/g), whether anthocyanins could be loaded on a solid phase to prevent its color fading was further tested. The results of Fourier transform infrared spectrophotometry (FT-IR) and differential scanning calorimetry (DSC) indicated that PPE was efficiently attached into the chitosan film. Meanwhile, adding CN (0.450%, w/v) into chitosan film could significantly enhance the tensile strength (TS), the water-resistant ability and the roughness of chitosan film. Whereas higher content of CN (0.600%, w/v) did not further improve mechanical properties and CN would distribute unevenly due to aggregation in the films. In addition to pH-indicating ability, CS-CN-PPE exhibited the extraordinary antioxidant activities and this provides another advantage of packaging readily oxidizable substances. Taken together, the current study provided a novel and biocompatible packaging with strengthened mechanical property and intelligent pH indicator.