Preparation and Application of a Sustained and Unidirectional Release Active Gelatin-Sodium Alginate/Zein Janus Film

Fresh walnuts are highly susceptible to microbial spoilage and oxidative browning, primarily due to their elevated moisture and fat content. To address this, an active Janus film (C film), fabricated from gelatin-sodium alginate and zein, was developed. This film provides a sustainable unidirectional moisture barrier and bacteriostatic properties. The active ingredient in C film is cinnamaldehyde (CIN). CIN showed 94.8% encapsulation efficiency in tannic acid nanoemulsions (CIN-Tas). Morphological analysis revealed hydrogen bonding between CIN-Tas and gelatin without significantly altering the film structure. The developed Janus film incorporating CIN-Tas exhibited enhanced thermal stability, antioxidant capacity, and mechanical properties. Water vapor permeability (WVP) values were 4.23×10 -7 and 1.49×10 -7 gPa -1 s -1 m -1 on either side, enabling external moisture barrier and internal moisture absorption. The CIN loaded films exhibited antimicrobial activity (inhibition zones: 3.19 cm against Penicillium cynodontis , 4.77 cm against Penicillium citrinum ). CIN release followed the Korsmeyer-Peppas model, sustaining release for 180 hours. A significant preservation effect was observed in fresh walnut storage experiments using C film coating. The decay rate was decreased by 20.34%. A decrease of 9.68% in malondialdehyde (MDA) content accumulation was recorded. Additionally, the rise in acid value (AV) and peroxide value (POV) was decreased by 25.21% and 7.99%, respectively. These results indicated that this packaging technology effectively inhibits microbial growth and maintains storage humidity, prolonging walnut freshness. It offers promising potential for extending food shelf life.