Low temperature extrusion blown ε-polylysine hydrochloride-loaded starch/gelatin edible antimicrobial films

Edible antimicrobial films made from starch/gelatin (S/G) incorporated with different epsilon-polylysine hydrochloride (epsilon-PL) contents were developed by low-temperature extrusion blowing process. epsilon-PL addition reduced the complex viscosity and storage modulus of blends, while promoted the formation of hydrogen bonding among film components. The control film had an A-type crystalline structure, while increasing the epsilon-PL content promoted its transformation to B-shaped structure. Without epsilon-PL and under the processing temperature used, the starch granules were not sufficiently gelatinized. However, epsilon-PL addition significantly enhanced the gelatinization degree. Increasing epsilon-PL content in S/G films increased film flexibility, water contact angle value, swelling degree, antimicrobial effect, and storage period of fresh bread, but decreased water vapor permeability and tensile strength. S/G film with 4 wt% epsilon-PL had the highest water contact angle (94 degrees) and elongation at break (149%). This research demonstrates the plasticizing effects of epsilon-PL and potential of S/G films containing epsilon-PL for food preservation/packaging.