Preparation and characterization of brewer's spent grain protein-chitosan composite films

Brewer's spent grain protein (BGP) was extracted from a by-product of beer production process and utilized as a biodegradable film source. To improve the physical and mechanical property of the BGP film, chitosan (Ch) was incorporated and the BGP-Ch composite films were prepared. Elongation at break (E) of the BGP composite films increased from 7.16 to 36.38 % as the BGP content increased, whereas tensile strength (TS) increased from 4.32 to 41.95 MPa as the chitosan content increased. In addition, the water vapor permeability (WVP) of the BGP composite films decreased with the increase of chitosan content. As a result, the optimum composition for the preparation of the BGP composite film was 3 % BGP and 2 % chitosan solutions at a ratio of 50BGP:50Ch, and its TS, E, and WVP were 23.71 MPa, 36.73 %, and 2.82 x 10(-9) g m/m(2) s Pa, respectively. The incorporation of chitosan into the BGP film inhibited the growth of Listeria monocytogenes, Staphylococcus aureus, Salmonella Typhimurium, and Escherichia coli O157:H7 compared to BGP films without chitosan. The composite films also had 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity. These results indicate that the BGP composite film can be used as an antimicrobial and antioxidative packaging material for foods.