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This study evaluated the effects of different levels of ultrasonic power (200, 400, 600 W) and treatment time (0, 10, 15 and 30 min) on the structure, emulsification characteristics, and in vitro digestibility of chickpea protein isolate (CPI). The changes in surface hydrophobicity of CPI indicated that ultrasound treatment exposed more hydrophobic amino acid residues. The analysis of sulfhydryl content and zeta potential showed that ultrasound caused the disulfide bond of CPI to be opened, releasing more negatively charged groups, and the solution was more stable. In addition, Fourier Transform Infrared Spectroscopy (FT-IR) and intrinsic fluorescence spectroscopy showed that ultrasound changes the secondary and tertiary structure of CPI, which is due to molecular expansion and stretching, exposing internal hydrophobic groups. The emulsification and foaming stability of CPI were significantly improved after ultrasonic treatment. Ultrasonic treatment had a minor effect on the solubility, foaming capacity and in vitro digestibility of CPI. All the results revealed that the ultrasound was a promising way to improve the functional properties of CPI.

The objective of the study was to research the effect of protein oxidation on the biochemical properties of Coregonus peled muscle proteins. Myofibrillar proteins (MP) prepared from C. peled back muscle was oxidized using a hydroxyl radical‐generating system (HRGS: 0.1 mM FeCl3, 0.1 mM ascorbic acid (Asc) and 1–20 mM H2O2). In the HRGS oxidizing system, the carbonyls, dityrosine content, and the surface hydrophobicity of C. peled MP (p < 0.05) increased with the increasing of H2O2 concentration and oxidation time, while the total sulfhydryl, free amino groups and the Ca‐ATPase activity decreased (p < 0.05). The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE) pattern reflected the formation of protein polymers and protein degradation. The results indicate that protein oxidation and the increasing levels of biochemical alterations of C. peled MP have influence on the quality of C. peled muscle protein. Practical applications Protein oxidation plays a major role in the meat quality deterioration of C. peled, which always leads to a change in protein physical and chemical properties. In this study, the biochemical change of MP isolates as affected by HRGS oxidation system was proposed. Such chemical modification leads to loss of protein amino groups, shift in the isoelectric point of the protein, loss of solubility and functionality. Additionally, protein carbonyls have been found to be potentially toxic to humans, and relevant measurement of dityrosine as those have been found to cause health problems after oral administration. So such modifications are of technological and nutritional relevance.

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