Valorisation of chestnut spiny burs and roasted hazelnut skins extracts as bioactive additives for packaging films

Abstract

The exploitation of agri-food by-products is a pertinent strategy in the context of the implementation of the circular economy concept in the agri-food industry. Therefore, the present work aimed to produce bioactive pullulan-based films loaded with polyphenolic-rich extracts from chestnut spiny burs (CSB, Castanea sativa Miller.) and roasted hazelnut skins (RHS, Corylus avellana L.). The hydroalcoholic extracts obtained from the CSB and RHS by-products were separately combined (1 %, 5 %, and 10 % w/w) with the filmogenic pullulan (PL) exopolysaccharide to fabricate flexible and bioactive films via simple solvent casting technique. The films present thermal stability up to 200 °C, good mechanical performance with Young’s modulus values higher than 2.6 GPa, and UV-light barrier properties. Furthermore, these flexible PL-based films exhibit a minimum antioxidant activity of ca. 94 % (DPPH scavenging activity) for the film composed of only 1 % of hydroalcoholic extracts (w/w relative to PL, i.e. 192 μg of extract per cm2 of film). Both sets of films were tested for antibacterial activity towards Staphylococcus aureus (a Gram-positive bacterium) and the results demonstrate antibacterial effectiveness with the increasing content of both hydroalcoholic extracts, reaching a maximum of 4–log CFU mL–1 reduction for the PL/RHS_10 film after 6 h. All the data evidences the potential applicability of these PL-based films containing hydroalcoholic extracts from agri-food by-products for the development of sustainable films for active food packaging.