Chestnut spiny burs and roasted hazelnut skins extracts as functional ingredients in bioactive packaging films

The agro-industrial processing produces large volumes of wastes and by-products. These last have attracted attention as excellent renewable source of active compounds with beneficial effects for human health. Thus, polyphenolic-rich extracts from chestnut spiny burs (CSB, Castanea sativa Miller.) and roasted hazelnut skins (RHS, Corylus avellana L.) were selected to design edible pullulan-based active films. Phenolic-containing extracts of CSB (rich in ellagic acid and chestanin) and RHS (rich in proanthocyanidins) present antioxidant activity and antifungal power against either polymorphic fungus Candida albicans and fungal strains causing plant infections, inhibiting the mycelial growth and spore germination of Alternaria alternata, Fusarium solani and Botrytis cinerea. The CSB and RHS hydroalcoholic extracts were separately combined (1 %, 5%, and 10% w/w) with the filmogenic pullulan (PL) exopolysaccharide to obtain flexible and bioactive films via simple solvent casting technique. The flexible PL-based 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, also showing a minimum antioxidant activity of ca. 94 % (DPPH scavenging activity) with a loading of only 1 % of hydroalcoholic extracts (w/w relative to PL, i.e. 192 μg of extract per cm2 of the film). The films also exhibited antibacterial activity towards Staphylococcus aureus as the hydroalcoholic extracts content increases, reaching a maximum 2 of 4–log CFU mL–1 reduction for the PL/RHS_10 film after 6 h. As result, PL-based films containing hydroalcoholic extracts from agri-food by-products are potential applicable in producing active food packaging.

Author(s): Tiziana Espositoa

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