Effect of chitosan conjugation on the functional properties and bactericidal activity of gluten peptides

Gluten was solubilized by chymotrypsin and the soluble peptides were purified and conjugated with chitosans of different degrees of polymerization through the Maillard reaction. High molecular weight-type chitosan (HMC) was found to be soluble at acidic pH and least soluble at neutral pH. However, after conjugation with gluten peptides, its solubility considerably improved at neutral pH while low molecular weight-type chitosan (LMC) conjugates were found to be soluble at both pHs. The emulsifying activity and emulsion stability of HMC conjugate were greatly improved at acidic pH compared to that of LMC. On the other hand, LMC conjugation slightly improved the emulsifying activity of gluten peptides at neutral pH compared to that of HMC. Despite its great efficiency in inhibiting the growth of Escherichia coli cells at high temperature, HMC conjugated with gluten peptides inhibited the growth of the bacterium cells, even at low temperature, significantly better than LMC conjugate.