Casein-caffeic acid-cellulose nanocrystals composite edible films for microwave food packaging application

Conventional microwave food packaging faces significant limitations in safety and degradability. This study investigated the potential of edible films for microwave food packaging by examining their structural and functional properties before and after microwave heating (800 W, 3 min). The films retained morphological integrity and exhibited slight structure and property deviations after microwave heating. Herein, cellulose nanocrystals (CNC) were incorporated into a casein-caffeic acid crosslinked network, forming a densified and stabilized film structure through physical entanglement and hydrogen bonding interactions. Incorporation of 3.75 wt% CNC enhanced the tensile strength by 21.80 % and reduced water vapor permeability by 17.20 % relative to the casein-caffeic acid film. The film containing 7.5 wt% CNC displayed noticeable CNC agglomeration within the matrix, which was alleviated after microwave heating. Concurrently, CNC addition mitigated the microwave-induced physical crosslinking in the films. All films exhibited antioxidant activity and antibacterial efficacy. In the braised beef packaging experiment, the films significantly mitigated mass loss in beef samples induced by microwave heating while effectively preserving their textural attributes. Collectively, the films demonstrate substantial potential as high-performance microwave food packaging materials.