Effects of Ultrahigh Pressure and Ultrasound Treatment on the Microstructure, Protein Oxidation, and Digestive Properties of Procambarus clarkii

This study aimed to investigate the effects of high-pressure processing (HPP) and ultrasound treatment on the microstructure, protein oxidation, and digestibility of Procambarus clarkii. Shrimp samples treated at different intensities were analyzed to assess changes in microstructure, water distribution, protein carbonyl and sulfhydryl contents, TBA value, SDS-PAGE profiles, secondary structure, protein digestibility, and average particle size, in order to elucidate the effects of the two processing methods on the microstructure and protein properties of shrimp. Results showed that both treatments disrupted the muscle fiber structure and led to water loss, and ultrahigh pressure treatment could cause more pronounced damage. Both treatments induced protein oxidation, as evidenced by a significant increase (P<0.05) in protein carbonyl content with increasing treatment intensity. Moreover, structural damage further increased carbonyl content during thermal processing. Low-intensity pressure and ultrasound favored the formation of ordered structures such as α-helices, while high-intensity treatments disrupted these structures, promoted protein aggregation, and increased the proportion of β-sheets. In terms of protein digestibility, shrimp treated with 50 MPs HPP and 100 W ultrasound exhibited relatively high digestibility values (69.53% and 66.48%, respectively). However, digestibility decreased progressively with increasing treatment intensity. In summary, both ultrahigh pressure and ultrasound treatment significantly affected the microstructure, protein oxidation, and digestibility of shrimp. Under the same increment of treatment intensity, ultrasound caused less structural damage and induced lower levels of protein oxidation during thermal processing, which might facilitate better recognition and binding by digestive enzymes, thereby improving protein digestibility.