Abstract: Pullulan (PUL) has strong hydrophilicity, so its films have high hygroscopicity. To address this limitation, κ-carrageenan (CAR) was introduced into the PUL matrix to prepare PUL/CAR composite films with CAR contents ranging from 0% to 14% by solution casting. The effects of CAR content on the structural characteristics, mechanical properties, heat-sealing performance, moisture absorption behavior, and solubility of the films were systematically investigated, and their application performance in peptide powder packaging was evaluated. The results demonstrated that the incorporation of 8% CAR formed a dense and well-compatible network structure with PUL by hydrogen bonding. Compared with pure PUL film, the P-8% CAR composite film exhibited enhanced tensile strength and elongation at break, along with a significantly reduced moisture absorption rate (from 12.28% to 8.92% at 81% relative humidity), an increased water contact angle, and decreased surface hydrophilicity. Although the introduction of CAR slightly prolonged the dissolution time, all composite films completely dissolved within 60 s, maintaining excellent fast solubility. After 7 days of storage, the moisture absorption rate of the peptide powder packaged with the P-8% CAR film increased only to 8.05%, indicating the film could effectively delay moisture-induced deterioration of the peptide powder, and the peptide powder still exhibited good instant solubility (complete dissolution within 90 s). In summary, the PUL/CAR composite film is an edible packaging film with relatively low moisture absorption, good mechanical properties, appropriate heat-seal strength, and rapid dissolution characteristics, providing a promising material choice and theoretical basis for green packaging of instant foods.

Key words: pullulan; κ-carrageenan; edible polysaccharide film; moisture absorption; fast solubility; heat sealing; food packaging