Abstract
The industrial processing of avocados annually generates more than 1.2 million tons of avocado peels (APs) and avocado seeds (ASs) that have great potential in the production of active bioplastics, although they have never been considered for this aim until now. Separately, the APs and ASs, as well as a combination of avocado peels and seeds (APSs), were evaluated here for the first time for the preparation of antioxidant films, with application in food packaging. Films were prepared by casting, after their processing by three different methods: (1) hydrolysis in acid media, (2) hydrolysis followed by plasticization, and (3) hydrolysis and plasticization followed by blending with pectin polymers in different proportions (25 and 50 wt %). The results indicate that the combination of hydrolysis, plasticization, and pectin blending is essential to obtain materials with competitive mechanical properties, optical clarity, excellent oxygen barrier properties, high antioxidant activity, biodegradability, and migration of components in TENAX suitable for food contact applications. In addition, the materials prepared with APSs are advantageous from the point of view of the industrial waste valorization, since the entire avocado wastes are used for the production of bioplastics, avoiding further separation processes for their valorization.
Highlights
The recovery of biomass from inedible fruit and vegetable wastes for the preparation of bioplastics is a growing research trend due to its expected positive impact on the environment through the circular economy model.[1−4] Bioplastics are defined as either biodegradable or biobased plastic materials or both
Nonsignificant differences were found in the WVP of plasticized avocado waste (AW) films and their composites with Low methoxyl pectin (LMP), but it was observed that permeability values were higher for materials prepared with avocado peels (APs), compared to avocado seeds (ASs) or APSs
The absence of significant differences among materials with the addition of LMP could be related to the presence of an AP- or AS-rich face, which is responsible for the WVP values, according to the results of TGA
Summary
The recovery of biomass from inedible fruit and vegetable wastes for the preparation of bioplastics is a growing research trend due to its expected positive impact on the environment through the circular economy model.[1−4] Bioplastics are defined as either biodegradable or biobased plastic materials or both. The bioplastics obtained from the processing of plant residues, without carrying out extractive processes, are biocomposites composed of numerous natural polymers and phytochemicals that can provide new functionalities to the developed materials, such as antioxidant, antimicrobial, and nutraceutical properties.[7] For this purpose, biomass is generally dried and milled to a powder form to inhibit the enzyme and bacterial activity and halt its decomposition during storage.[8] Bioplastics cannot be directly obtained from this dried form, given the absence of thermoplasticity; different methods have been proposed for its dissolution or digestion.[2,4,9] Among them, the acid hydrolysis stands out, which allows obtaining bioplastics through the disruption of plant cell walls, partial hydrolysis of constituent polymers, and release of cellulose microcrystals.[2] This process commonly results in a viscous solution, and films are obtained by casting or other drying techniques This method, especially when mild acids are used, is highly sustainable since the entire process is carried out in aqueous solutions, and the acid solution employed may be recovered by vapor collection during the drying of the films
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