Effect of heat treatment on chemically modified proteins of legume seeds

Legume proteins (unmodified and chemically modified) were subjected to heat treatment (100 °C, 60 min). The effects of heating on the protein solubility, the amino nitrogen content and UV spectra were studied. The protein solubility decreased after heat processing. The amino nitrogen content increased after heating of unmodified proteins, indicating polypeptide chain unfolding. But chemical modification resulted in a decrease of this form of nitrogen, suggesting that protein chains were involved. UV spectra indicate exposure of phenylalanine residues in heated unmodified and chemically modified proteins. Acetylation enhanced thermal denaturation and acetylated pea proteins showed an especially high sensitivity to heat.