Effect of frying process on in vitro protein digestibility of traditional Chinese tofu through remodelling protein structure at multiscale

Abstract

SummaryThe objective of this study was to investigate the effect of frying temperature (110, 130, 150, 170, or 190 °C for 3 min) and time (1, 3, or 5 min at 170 °C) on the protein structure and in vitro protein digestibility of traditional Chinese tofu. The results indicated that frying caused the formation of disulfide bonds and loss of ionic bonds, hydrogen bonds, and hydrophobic interactions. The FTIR pattern, surface hydrophobicity, and endogenous fluorescence of tofu changed with frying temperature and time, which verified the protein unfolding and thus provided a prerequisite for subsequent protein reaggregation during the frying process. Scanning electron microscopy showed that the destruction and formation of protein aggregates in fried tofu were regulated by the frying temperature and time. Moderate frying conditions, including frying at 110, 130, or 150 °C for 3 min, or frying at 170 °C for 1 min, improved the protein digestibility of tofu through remodelling protein structure at multiscale. This work provided a valuable insight into the preparation of fried tofu with high quality.