Cellulose nanocrystals from Actinidia deliciosa pruning residues combined with carvacrol in PVA_CH films with antioxidant/antimicrobial properties for packaging applications

Abstract

Kiwi Actinidia deliciosa pruning residues were here used for the first time as precursors for the extraction of high performing cellulose nanocrystals (CNC) by applying a bleaching treatment followed by an acidic hydrolysis. The resultant cellulosic nanostructures, obtained by an optimize extraction procedure (0.7% wt/v two times of sodium chlorite NaClO2) followed by an hydrolysis step, were then used as reinforcements phases in poly(vinyl alcohol) (PVA) blended with natural chitosan (CH) based films and also combined, for the first time, with carvacrol used here as active agent. Morphological and optical characteristics, mechanical response, thermal and migration properties, moisture content and antioxidant and antimicrobial assays were conducted. The morphological, optical and colorimetric results underlined that no particular alterations were induced on the transparency and color of PVA and PVA_CH blend by the presence of CNC and carvacrol, while they were able to modulate the mechanical responses, to induce antioxidant activities maintaining the migration levels below the permitted limits and suggesting the possible application in industrial sectors. Finally, inhibitions on bacterial development were detected for multifunctional systems, suggesting their protective function against microorganisms contamination.