A biodegradable film based on sodium alginate-gelatin involving a mulberry anthocyanin extract for fish oil packaging

Abstract

Driven by the 'dual carbon' strategy and the imperative of a circular economy, food packaging is undergoing a ternary upgrade. In this study, mulberry anthocyanin extract (MAE) was upcycled into a natural, dual-function active principle that concurrently delivers antioxidant capacity and ultraviolet (UV) barrier activity. It was incorporated with an edible sodium alginate-gelatin (SG) based film to engineer a next-generation biodegradable antioxidant film. The dose-dependent impacts of MAE on the film's mechanical signature, radical-scavenging efficacy, optical performance, and practical utility in fish oil packaging were systematically examined. MAE obtained from a residue of mulberry juice fermentation had 296.86 mg/g total polyphenols and 146.50 mg/g anthocyanins, primarily cyanidin-3-glucoside and cyanidin-3-rutinoside. When 0.2 mg/mL MAE (SG-2MAE) was added, the tensile strength of SG films increased from 48.33 to 50.98 MPa. When 0.4 mg/mL MAE was incorporated, the antioxidant activity of SG-4MAE film against 2,2'-biazido-bis-3-ethyl-benzothiazoline-6-sulfonic acid (ABTS) increased by 158%, whereas transmittance (600 nm) decreased by 33.7%, indicating enhanced UV blocking. When applied for packaging fish oil, the SG-MAE film delayed oxidation better than the unpackaged sample after 4 weeks' storage by directly blocking oxygen, releasing antioxidant constituents, and adsorbing residual oxygen. In summary, SG-MAE films showed excellent comprehensive properties and high antioxidant properties, and could be used as active packaging materials for fish oil.

Keywords

Active packaging / Antioxidant activity / Fish oil / Mulberry anthocyanins / Shelf life extension

Author contributions

The authors confirm their contributions to the paper as follows: writing - review & editing: Lv Y; draft manuscript preparation: Lv Y, Yang J, Luo T; investigation: Lv Y, Liao H; methodology: Yang J, Liao H; conceptualization, supervision, project administration, funding acquisition: Liao H. All authors reviewed the results and approved the final version of the manuscript.

Data availability

The datasets generated during and/or analyzed in the current study are available from the corresponding author on reasonable request.

Acknowledgments

This work was supported by the Innovation and Entrepreneurship Training Program for College Students in Jiangsu Province (Grant No. 202410295126Y).

Conflict of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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