# Antioxidant Biocomposite Films Based on Grape Stalk Lignocellulosic Fractions and Biodegradable Polyesters

## TL;DR

This paper explores using grape stalk waste to create antioxidant-rich biocomposite films for food packaging that can preserve oils and block UV light.

## Contribution

The study introduces grape stalk-based biocomposites with antioxidant properties for food packaging applications.

## Key findings

- Grape stalk particles improved the oxygen barrier and UV protection of biocomposite films.
- Fillers increased stiffness but reduced extensibility and thermal stability in PBS and PHBV films.
- Antioxidant compounds migrated from grape stalk particles in PHBV composites.

## Abstract

Grape stalk (GS) from winemaking is a waste rich in antioxidant compounds that can be valorized to obtain active food packaging materials. Biocomposite films of poly (butylene succinate) (PBS) and poly(3-hydroxybutyrate)-co-hydroxyvalerate (PHBV) with 10% of GS particles, previously submitted or not to subcritical water extraction at 170 °C and 180 °C, were obtained by melt blending and characterized. The fibres were better integrated in the PHBV matrix than in PBS, while other molecular compounds from the fillers were released to the polymer matrix, allowing for their antioxidant action. Fillers promoted the stiffness of PBS films (11–44%), reducing their resistance to break and extensibility by 25%, without significant changes in polymer crystallinity or thermal stability. However, this reduced the crystallinity (13%) and thermal stability of PHBV films, decreasing their rigidity (55%). All fibres promoted the oxygen barrier capacity in composites (by about 20–35% for PBS and PHBV, respectively) while also providing them with UV light blocking effects. This barrier effect enhanced the ability of the films to preserve sunflower oil against oxidation, while in PHBV composites, the migration of antioxidant compounds was also detected. No remarkable differences in the effects of the different GS fillers on the properties of composites were detected.