Enzymatic grafting of peptides from casein hydrolysate to chitosan. Potential for value-added byproducts from food-processing wastes.

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TitleEnzymatic grafting of peptides from casein hydrolysate to chitosan. Potential for value-added byproducts from food-processing wastes.
Publication TypeJournal Article
Year of Publication2004
AuthorsAberg, CM, Chen, T, Olumide, A, Raghavan, SR, Payne, GF
JournalJ Agric Food Chem
Volume52
Issue4
Pagination788-93
Date Published2004 Feb 25
ISSN0021-8561
KeywordsCaseins, Catalysis, Chitin, Chitosan, Food Handling, Industrial Waste, Monophenol Monooxygenase, Peptides, Rheology
Abstract

Tyrosinase was used to initiate the grafting of peptides onto the amine-containing polysaccharide chitosan. Chemical evidence for covalent grafting was obtained from electrospray mass spectrometry for products formed from reactions with glucosamine (the monomeric unit of chitosan) and the model dipeptide Tyr-Ala. When this model dipeptide was incubated with tyrosinase and chitosan, there was a marked increase in the viscosity of the solution. This viscosity increase provides physical evidence that tyrosinase can initiate peptide grafting onto the chitosan backbone. A peptide-modified chitosan derivative was generated by reacting chitosan (0.32 w/v%) with acid-hydrolyzed casein (0.5 w/v %) using tyrosinase. After reaction, the peptide-modified chitosan was partially purified and dissolved in an aqueous acetic acid solution. Low concentrations of this peptide-modified chitosan were observed to confer viscoelastic properties to the solutions. Specifically they conferred high viscosities and shear thinning properties to the solutions, and solutions containing only 1 w/w % of the peptide-modified chitosan behaved as weak gels. Thus, tyrosinase provides a simple and safe way to convert food-processing byproducts into environmentally friendly products that offer useful functional properties. The selectivity of tyrosinase and the relatively high reactivity of chitosan's amines allow grafting to be performed with uncharacterized peptide mixtures present in crude hydrolysates.

DOI10.1021/jf034626v
Alternate JournalJ. Agric. Food Chem.
PubMed ID14969532