Tokyo University of Marine Science and Technology Graduate
Physical and Chemical Properties of Edible Protein Films
Containingε-Polylysine Made From Blue Marlin (Makaira mazara)
【Objective】The increase in food-born microbial outbreaks has intensified the researches on antimicrobial packaging technology. The antimicrobial packaging is prepared by adding antimicrobials to food packaging.
ε-Polylysine is a homo-poly-amino acid produced by Streptomyces albulus . This natural compound is reportedly stable at high temperature and under acidic or alkaline conditions and has a wide antimicrobial spectrum, including Gram-positive and Gram-negative bacteria. In this research, the effect of
ε-polylysine added to blue marlin protein films on their physical and chemical properties was investigated.
【Methods】Fish protein films were prepared from the flesh of blue marlin (Makaira mazara). Film-forming solutions (FFS) containing 2% protein and 0.5% glycerol were prepared. ε-Polylysine was added to FFS at 2.5, 5, 7.5, or 10% (w/w) of protein prior to pH adjustment to alkali using 1 M NaOH (pH 11) or to acidic using 1M HCl (pH 3). Then, FFS were cast on rimmed silicone plates and dried at 25℃for 24 h. The following properties were determined; tensile strength (TS), elongation at break (EAB), water vapor permeability (WVP), color, and SDS-PAGE. Also the release of ε-polylysine from films in distilled water at 30℃ was determined.
【Results】In general, the addition of ε-polylysine did not affect TS, EAB, WVP, and color properties. The release of ε-polylysine from films showed that it increased with increasing concentration of ε-polylysine in films. It was also estimated that a fixed amount (about 20 μg) of ε-polylysine was reacted per mg of protein. SDS-PAGE showed no difference between control films and films containing ε-polylysine, suggesting that the amount of ε-polylysine added to films is not enough to induce the polymerization of proteins. The next step of this study is to determine the antimicrobial properties of films.