Development of pH-sensitive colorimetric bioindicator antimicrobial films from oak tree acorn starch, red onion peel extract and methyl cellulose for freshness monitoring of chicken meat.

The research on finding alternative natural and inexpensive materials for the development of biodegradable intelligent food packaging materials is increasing day by day to reduce plastic waste in the environment. In this study, new oak tree acorn starch-based films (S) with pH-sensitive and antimicrobial property were developed using oak tree acorns, quercetin (QUE) extract obtained from red onion peel and ZnO nanoparticles and their physicochemical, mechanical, thermal and barrier properties were compared with those of methyl cellulose-based films. S-QUE film having colorimetric pH-indicator property showed an obvious color variation from pink to green/yellow at different pH values (pH 1-12). Compared to S film, the maximum tensile stress and maximum tensile strain values of the S-QUE film increased by 93.34 % and 296.56 %, respectively. The presence of QUE extract in the film matrix increased the thermal stability of films and ZnO nanoparticles decreased it. The use of QUE extract and ZnO nanoparticles in film formulation led to an improvement in the water vapor barrier properties of films. The effectiveness of S-QUE and S-QUE-ZnO films in monitoring the spoilage of chicken meat was tested. These films showed visible color responses as the chicken meat spoiled.