Packaging is fundamental to product protection and supply chain integrity [1]. While plastics have become ubiquitous due to their cost-effectiveness, versatility, and mechanical robustness, their dominance creates significant challenges. Approximately 40% of global plastic production is dedicated to packaging, with the majority serving the food sector [2]. However, escalating consumer awareness regarding health risks and the environmental crisis driven by plastic waste has necessitated the development of sustainable, renewable bio-based alternatives that meet rigorous performance standards [3], [4]. Consequently, protein-based natural polymers have garnered attention for application as edible films and coatings [5]. These materials integrate barrier functionality with biodegradability and inherent nutritional value, positioning them as a promising green technology for food preservation.

Zein, a prolamin derived from corn, is distinguished by its unique film-forming capabilities, which arise from its specific molecular structure and high proportion of hydrophobic amino acids. These attributes render it an excellent candidate for developing biodegradable food packaging [6]. Nevertheless, the industrial utility of pure zein films is restricted by their inherent brittleness and susceptibility to moisture [7], limiting its practical application. To address these mechanical deficiencies, plasticizers such as glycerol, glucose, and oleic acid are conventionally employed [8], [9], [10]. Beyond simple plasticization, structural modification is often required; Tannic acid (TA), a food-grade natural polyphenol [11], functions as a potent cross-linking agent. It enhances the physicochemical integrity of protein networks through hydrogen bonding and hydrophobic interactions between its hydroxyl groups and the protein's amino acid residues [12]. Furthermore, to bolster moisture resistance, fatty acids are frequently introduced. The incorporation of biopolymers such as stearic acid (SA) can significantly augment the hydrophobicity and antioxidant capacity of the matrix due to its long-chain aliphatic structure [13]. To impart active preservation functions, lemongrass essential oil (LEO) offers broad-spectrum antibacterial properties. With diverse sourcing and established extraction protocols, LEO serves as a natural preservative [14], and its integration into an edible coating matrix maximizes its efficacy in inhibiting microbial growth on fresh produce.

Cherry tomatoes are highly perishable, characterized by high postharvest respiratory rates, thin skins, and substantial moisture content, rendering them vulnerable to mechanical injury, desiccation, softening, and microbial spoilage [15]. Therefore, developing effective preservation strategies to mitigate post-harvest losses is imperative. While existing literature reports on composite films combining zein, tannic acid, and essential oils, these systems often prioritize antibacterial efficacy at the expense of moisture barrier performance [16], [17], [18], [19], a critical parameter for preventing dehydration in fresh produce.

This study addresses this gap by developing a multifunctional composite coating based on zein, synergistically modified with tannic acid, stearic acid, and lemongrass essential oil to achieve a balance between hydrophobicity and antimicrobial activity. We conducted a comprehensive investigation into the mechanical strength, barrier properties, surface hydrophobicity, thermal stability, and antibacterial performance of the composite films. Furthermore, the practical efficacy of the coating was evaluated on cherry tomatoes during storage, monitoring key quality indicators. These findings offer valuable insights and a technical framework for the advancement of environmentally sustainable and high-efficiency food packaging systems.