Multi-mechanism cross-linking driven chain spacing shortening to construct polysaccharide-based active packaging films with high water resistance and intelligent controlled release

Polysaccharide-based active packaging materials have extensively explored in the field of food safety, whereas the highly hydrophilic traditional biopolymer was susceptible to be broken under moisture conditions, leading to the invalid food preservation. Herein, a multi-mechanism cross-linking densification strategy was employed to design and construct novel carboxymethyl chitosan (CMCS)/sodium alginate-dopamine complex (SD)/oxidized starch (OS)/tea polyphenol (TP) composite film (COSDT) composite. Multiple cross-linking reduces the spacing between polysaccharide chains to make the structure denser, hindering the adsorption and penetration of water molecules. The optimized COSDT-2 film maintains intact structures without any dissolution after immersing in water for 24 h and demonstrated relatively stable water contact angle of 71.97° at 1 s and 68.48° after 60 s. The water vapor permeability and oxygen transmission rate were reduced from 5.10 × 10 −7  g m −1  s −1  Pa −1 and 8.28 cm 3  μm (m 2  day KPa) −1 for COT sample to 1.03 × 10 −7  g·m −1 ·s −1 ·Pa −1 and 2.70 cm 3  μm (m 2  day KPa) −1 for COSDT-2 film. Moreover, COSDT films exhibited stable wet mechanical properties in high-humidity environments (95 % RH) of 30.76 MPa. COSDT-2 accelerated the release of tea polyphenols by structural loosening due to enhanced interchain repulsion under alkaline conditions, resulting in a significant reduction of volatile alkaline nitrogen production by 61.58 % in chicken breast meat and prolonged shelf life. This study provided a novel perspective in designing and constructing water-resistant active food packaging biofilms through modulating the interchain spacing of polymers.