In recent years, ultrasound has been widely used in the food industry as a promising non-thermal, green technology, but the exact effect of ultrasound on the physicochemical properties of myofibrillar proteins from Procambarus clarkii is not clear yet. This study investigated the effect of high-intensity ultrasound treatment at 300 W power and 20 kHz frequency for 0, 4, 8, 12 and 16 min during homogenization on the structure and physicochemical properties of myofibrillar proteins from Procambarus clarkii. The results showed that ultrasound treatment decreased the turbidity and mean particle size of myofibrillar proteins significantly (P < 0.05), but initially increased and then decreased the solubility and absolute value of ζ-potential, demonstrating altered degree of protein aggregation. The surface hydrophobicity and endogenous fluorescence intensity initially increased and then decreased with increasing treatment time; the total sulfhydryl group content significantly decreased (P < 0.05) while the carbonyl group content significantly increased (P < 0.05), demonstrating changes in the tertiary structure and a certain degree of protein denaturation. In addition, the relative contents of α-helix and random coil increased first and then decreased, whereas the opposite trend was observed for the proportion of β-sheet, indicating changes in the secondary structure. These results showed that high-intensity ultrasound treatment could affect the physicochemical properties, structure and aggregation degree of myofibrillar proteins from crayfish meat, which could provide a reference for the application of ultrasound as an auxiliary approach in the processing and storage of crayfish.

In this study, the effects of the addition of different amounts of salt (0%, 1%, 2% and 3%) at five stages of processing: raw shrimp, blanching, marination, soaking for 2 h and soaking at 4 ℃ for 24 h, on the quality and volatile flavor compounds of marinated crayfish were investigated. The results showed that L^* values increased and then decreased as the processing stages proceeded, while a^* and b^* values both continued to increase. But salt addition had little effect on the color difference. Additionally, moisture content decreased and then increased, and was affected little by salt addition. For 1%, 2%and 3% salt addition, hardness, elasticity, chewiness and adhesion showed an initial increasing and subsequent decreasing trend. Without salt addition, hardness and chewiness continued to increase. For each group, elasticity and cohesiveness increased and then did not show any significant change. The electronic nose results could be roughly divided into four parts, raw shrimp and blanching, marination, soaking for 2 h, and soaking at 4 ℃ for 24 h. There were also some differences between the less and more salt addition groups. The electronic tongue results showed that as salt addition increased or the processing stages proceeded, saltiness, astringency, and umami taste increased, and other taste attributes changed little. Gas chromatography-ion mobility spectrometry (GC-IMS) analysis showed that salt addition and marination had a positive effect on the volatile flavor of crayfish. However, excessive salt addition and too long processing time were detrimental to volatile flavors. In conclusion, the addition of salt and processing stages can affect the quality and flavor of marinated crayfish.