Study on the formation mechanism of pea protein nanofibrils and the changes of structural properties of fibril under different pH and temperature

The functional performance of plant proteins can be enhanced by converting them into nanofibrils using controlled acid-heat treatments. Initially, the impact of heating time on the morphology and properties of nanofibrils prepared from pea proteins was assessed. The pea protein nanofibrils (PPF) were formed by heating at 85 °C and pH 2.0 for different times (0–24 h). Multiple analytical methods were then used to characterize the properties of the nanofibrils, including transmission electron microscopy (TEM), gel electrophoresis (SDS-PAGE), thioflavin T (ThT) fluorescence spectroscopy, molecular flexibility, and surface hydrophobicity. With increasing heating time, the protein molecules were gradually decomposed into small molecular weight peptides, which then assembled into nanofibrils. Initially, the length of the PPFs increased with heating time, but then it decreased, which was attributed to fibril fragmentation. In the food processing industry, pH and temperature are important factors affecting food preparation. For this reason, the effects of pH (2–9) and temperature (55, 85, 100 °C) on the properties of the nanofibrils were explored. These environmental conditions had a strong influence on the morphology and properties of PPFs. For instance, their flexibility increased with increasing pH, whereas their surface hydrophobicity decreased with increasing pH and temperature. Moreover, their charge went from positive to negative as the pH was ascended from below to above their isoelectric point. The findings of the structural properties of protein nanofibrils could provide some new insights into the wider application of nanofibrils in the food industry.