Chitosan complexes with amino acids and whey peptides: Sensory and antioxidant properties

Chitosan reacts with amino acids and hydrolyzed whey proteins to produce biologically active complexes that can be used in functional foods. The research objective was to obtain chitosan biocomposites with peptides and amino acids with improved antioxidant and sensory properties. The research featured biocomposites of chitosan and succinylated chitosan with whey peptides and amino acids. The methods of pH metry and spectrophotometry were employed to study the interaction parameters between polysaccharides and peptides, while colorimetry and spectrophotometry served to describe the amino acids content. The antiradical effect was determined by the method of fluorescence recovery. Pure compounds and their complexes underwent a sensory evaluation for bitterness. Chitosan and succinylated chitosan formed complexes with whey peptides and such proteinogenic amino acids as arginine, valine, leucine, methionine, and tryptophan. The equimolar binding of tryptophan, leucine, and valine occurred in an aqueous chitosan solution (in terms of glucosamine). Methionine appeared to be the least effective in chitosan interaction, while arginine failed to complex both with chitosan and succinylated chitosan. Chitosan and succinylated chitosan biocomposites with peptides and leucine, methionine, and valine proved to be less bitter that the original substances. The samples with arginine maintained the same sensory properties. Chitosan complexes with tryptophan and peptides increased their antioxidant activity by 1.7 and 2.0 times, respectively, while their succinylated chitosan complexes demonstrated a 1.5 fold increase. Chitosan and succinylated chitosan biocomplexes with tryptophan and whey protein peptides had excellent antioxidant and sensory properties. However, chitosan proved more effective than succinylated chitosan, probably, because it was richer in protonated amino groups, which interacted with negatively charged amino acids groups.