Red pepper waste-derived carbon dots incorporated sodium alginate/ gelatin composite films for bioactive fruit preservation

The design of cost-efficient and eco-friendly packaging films with multifunctional features such as antimicrobial, antioxidant, and UV protection is important in food industry. Red pepper waste-derived carbon dots (RP-CDs) have been used as reinforcement and active components in the fabrication of advanced packaging materials. The synthesized spherical RP-CDs with an average diameter of 2.5 nm were rich in active functional groups such as -NH2, -OH, -C=O, C-O, and C-O-C. Casting method was used to load 1, 2, and 3 wt% of RP-CDs into sodium alginate/gelatin (SA/Gel) polymer matrix. SEM images and FT-IR and XPS analyses confirmed the strong compatibility and potential hydrogen bonding between RP-CDs and the matrix. This interaction improved the mechanical strength and moisture resistance of the composite films. With the addition of 3 wt% RP-CDs, the UVA barrier, ABTS radical scavenging, and L. monocytogenes bactericidal properties of the composite film increased by 92.5, 100, and 99.9 %, respectively. Fruit preservation results revealed that the prepared SA/Gel/RP-CD3% composite film maintained the freshness of packed grapes and extended their storage life to 24 days. The development of active packaging films with biowaste-derived functional fillers (CDs) offers the dual benefit of extending the shelf life and contributing to food waste management.