Casein hydrolyzate augments antimicrobial and antioxidative persistence of cheddar whey protein concentrate based edible coatings

Hydrolysis of casein using chymotrypsin results in the formation of polypeptides (casein hydrolyzate, CH) with a hydrophobic aromatic amino acid on one end of the chain because the enzyme selectively cleaves the adjacent peptidebond. Due to resonance of the aromatic micro-domain, thiols become redox-sensitive and actively participate in electron transfer. These types of amphipathic peptides also tend to be membrane-lytic. The two prong approach of this investigation was to, (1) assess antibacterial effect of the CH in beef steak, and (2), to determine its antioxidative efficacy as a constituent of Cheddar whey based edible coating mix. Coliform growth, using shoulder-cut beefsteaks as model, showed a significant (P<0.05) five log reduction to log CFU<1 even at its lowest concentration range (0.15-0.2 %) (w/v). Radical quenching ability reflected by increasedn time required for maximal alkoxyland peroxyl-radical accumulation in reaction mixtures without and with CH, by in vitro pyrolysis of 2, 2’-Azo-bis (2-amidinopropane), was six minutes even at its lowest trace concentration (0.1 %, w/v) indicating dramatic enhancement of long-term antioxidative persistence. At the same concentration, CH augmented 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging efficacy of the film by 28%. The study showed the potential for beneficial use of CH in dramatically enhancing efficacy of WPC based edible coatings to reduce microbial and oxidative degradation of muscle foods during retail-cut processing and display.