Orange peel waste biorefinery in multi-component cascade approach: Polyphenolic compounds and nanocellulose for food packaging

Abstract

This study proposed an efficient valorization of orange peel waste (OPW) thorugh a multi-product cascade biorefinery approach. In a first step, polyphenolic-rich bioactive extract was obtained using 100% ethanol after a suitability study of different solvent systems. Its use in ultrasound-assisted extraction at 80 °C also allowed obtaining bioactive extracts with higher characteristics and reducing the extraction time (30 min) compared to conventional extraction (5 h). The extractives free-OPW was then used to obtain nanocellulose with high yield (>70%), solely by subjecting the fiber to a high-pressure homogenization treatment without the need for additional pretreatments, highlighting the efficiency of the process. The different components obtained were used separately and together on poly(vinyl alcohol)-based (PVA) films to study the isolated and synergistic effect they contributed to the properties of the films. The optimum cellulose nanofibers (CNF) content was found to be 5%, at higher contents a tendency to clustering of the nanofibers in the matrix was observed. The addition of polyphenol-rich extracts conferred interesting bioactive properties of special interest for food packaging. The antioxidant properties of the films increased as the extract content in the formulation increased, reaching almost 100% for an extract content of 30%. Also, UV-light blocking capacity was increased reaching values of 100% for extract contents above 20%. The synergistic effect of the joint addition of CNF and polyphenols resulted in bioactive films with high UV-blocking capacity that maintained the structural and mechanical properties of pure PVA films. Regarding the antioxidant capacity, a more controlled release action is observed. These results evidenced that the synergistic effect between bioactive extracts and CNF could be an excellent enhancer of the active packaging.