Lignocellulose Nanofibre Obtained from Agricultural Wastes of Tomato, Pepper and Eggplants Improves the Performance of Films of Polyvinyl Alcohol (PVA) for Food Packaging

Abstract

Films formulated with polyvinyl alcohol (PVA) (synthetic biopolymer) were reinforced with lignocellulose nanofibres (LCNF) from residues of vegetable production (natural biopolymer). The LCNF were obtained by mechanical and chemical pre-treatment by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and added to the polyvinyl alcohol (polymer matrix) with the aim of improving the properties of the film for use in food packaging. The mechanical properties, crystallinity, thermal resistance, chemical structure, antioxidant activity, water barrier properties and optical properties (transparency and UV barrier), were evaluated. In general, with the addition of LCNF, an improvement in the studied properties of the films was observed. In terms of mechanical properties, the films reinforced with 7% LCNF TEMPO showed the best results for tensile strength, Young’s modulus and elongation at break. At the same LCNF proportion, the thermal stability (Tmax) increased between 5.5% and 10.8%, and the antioxidant activity increased between 90.9% and 191.8%, depending on the raw material and the pre-treatment used to obtain the different LCNF. Finally, a large increase in UV blocking was also observed with the addition of 7% LCNF. In particular, the films with 7% of eggplant LCNF showed higher performance for Young’s modulus, elongation at break, thermal stability and UV barrier. Overall, results demonstrated that the use of LCNF generated from agricultural residues represents a suitable bioeconomy approach able to enhance film properties for its application in the development of more sustainable and eco-friendly food packaging systems.

Renovation of Agro-Waste for Sustainable Food Packaging: A Review

“…The utilization of agricultural and food industry residues as a rich source of biopolymers such as cellulose, starch, fiber, and protein can be obtained by mechanical (milling [ 56 , 57 , 58 ]) and chemical (ethanol extraction [ 59 ], acid extraction [ 60 ], alkaline extraction [ 61 ]) treatments. Using reinforcements obtained from agricultural waste becomes of greater interest when used to enhance the properties of bio-based food packaging materials in terms of mechanical and thermal resistance, water absorption, and barrier and biodegradation properties [ 61 , 62 , 63 , 64 ].…”

“…However, the agglomeration of lignocellulose [ 61 ] and sweet potato residue fillers [ 58 ] in bioplastic leads to a breakdown of the interaction of the two matrices that results in a weak interphase adhesion and loss in mechanical properties. Thus, mechanical properties are largely improved due to (i) the stiffness of fillers, (ii) the strong hydrogen bonding between the reactive hydroxyl groups of the fillers and the polymer matrix, and (iii) the compatibility and homogeneous dispersion of fillers in the polymeric matrix [ 63 , 64 ].…”

“…Thermal degradation can lead to other properties (i.e., mechanical strength and barrier properties) gradually deteriorating. Lignocellulose nanofibers from eggplant crop residues obtained by mechanical pre-treatment enhanced the degradation temperature of poly (vinyl alcohol) film, which provides better thermal stability to the reinforced composites due to the major presence of lignin establishing covalent bonds with cellulose [ 64 ]. Starch and cellulose fillers from sweet potato residues showed decreases in both the decomposition temperature and the degradation rate of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) composites.…”

Lignin-containing biodegradable UV-blocking films: a review

“…One is directly made of the LCNF (lignocellulosic nanofibril) containing lignin and cellulose naturally, and the other is the composite material that combines the separated lignin and cellulose artificially. [68][69][70][71][72] 3.1.1.1. Preparation directly from the LCNF Biodegradable LCNF films share remarkable properties with plants, boasting excellent anti-ultraviolet and mechanical characteristics.…”

“…One is directly made of the LCNF (lignocellulosic nanofibril) containing lignin and cellulose naturally, and the other is the composite material that combines the separated lignin and cellulose artificially. 68–72…”