# Interaction of Hazelnut-Derived Polyphenols with Biodegradable Film Matrix: Structural, Barrier, and Functional Properties

## TL;DR

This study shows how hazelnut by-products can be turned into biodegradable films with improved food preservation properties using eco-friendly extraction methods.

## Contribution

A novel valorization strategy for hazelnut by-products using PHWE to create functional biodegradable films with enhanced barrier and antioxidant properties.

## Key findings

- Polyphenol incorporation reduced oxygen permeability by 69% and increased antioxidant activity five-fold.
- Films with hazelnut polyphenols showed significant microbial growth reduction in fresh-cut foods during storage.
- Optimal formulations improved flexibility and elongation at break by 39% without compromising transparency.

## Abstract

The study presents a sustainable approach to valorizing hazelnut processing by-products, specifically skins and shells, through their conversion into bioactive polyphenol-rich extracts using pressurized hot water extraction (PHWE), an environmentally friendly green technology. PHWE yielded extracts with total phenolic contents of 25.4 mg GAE/g dw (shell) and 83.7 mg GAE/g dw (skin), which were incorporated into biodegradable poly(vinyl alcohol)/carboxymethyl cellulose (PVA/CMC) films at concentrations of 1–3% (w/v). The resulting composites were comprehensively characterized in terms of structural, mechanical, thermal, and barrier properties. FTIR, DSC, and XRD analyses demonstrated strong hydrogen bonding, increased thermal stability, and reduced crystallinity due to polyphenol–polymer interactions. Phenolic incorporation enhanced UV-blocking capability, increased antioxidant activity by up to five-fold, and reduced oxygen permeability from 0.048 to 0.015 (cm3·mm·m−2·day−1·atm−1) (69% reduction, p < 0.05), compared to neat PVA while maintaining desirable transparency (>70%). Optimal formulations (HSkE-II) exhibited a 39% increase in elongation at break and improved flexibility without compromising film integrity. Application tests using fresh-cut apples, watermelon, and chicken revealed significant reductions in microbial growth (up to ~1.2 log CFU/g), lipid oxidation, and weight loss during storage, confirming the films’ potential for active food packaging. This work highlights an efficient valorization strategy for nut industry by-products and demonstrates their functional integration into sustainable biodegradable packaging systems.