Effects of dry heating on the progression of in vitro digestion of egg white proteins: contribution of multifactorial data analysis

The impact of dry heating on the progression of in vitro digestion of egg white proteins was investigated through application of multiple factor analysis (MFA) to electrophoresis data. Dry heating (from 1 to 10 days between 60 and 90 °C) enhanced protein unfolding and aggregation, thus generating different SDS-PAGE patterns for each sample before digestion. The progression of in vitro digestion was then modified according to the degree of protein unfolding and/or aggregation. In vitro digestion tended to decrease the heterogeneity of sample electrophoretic patterns overall but it occurred either at the very beginning of the gastric stage or throughout the gastric stage or again during the duodenal stage, depending on the heat treatment to which the sample had been subjected. At the end of digestion, three groups of samples were obtained: all samples dry heated at 60 °C and one sample dry heated for 1 day at 70 °C that were more hydrolysed than the control, samples dry heated for more than 2 days at 80 °C or 90 °C that were less hydrolysed than the control, and samples dry heated for more than 2 days at 70 °C or 1 day at 80 or 90 °C that were as hydrolysed as the control.