Starch-octenyl succinic anhydride nanoemulsions with clove and white thyme essential oils: In vitro antifungal activity and application on orange (Citrus sinensis cv. Salustiana) preservation

Abstract

Starch modified by octenyl succinic anhydride (OSA) is a polysaccharide that can be used as a stabilizer in the development of emulsions added with essential oils (EOs). The objective of this study was to develop nanoemulsions based on starch-OSA containing clove essential oil (CEO) and white thyme essential oil (WTEO) and a proportional mixture of the two EOs (CWTEO) using high-pressure homogenization. The emulsions were characterized by particle size, zeta potential, polydispersity index, stability during 150 days, and antifungal activity, with inhibition of mycelial growth, against the fungus Penicillium digitatum. The addition of WTEO and CWTEO in concentrations of 1.5 and 2 % allowed the formation of stable nanoemulsions, with particle sizes ranging from 72 to 293 nm. These nanoemulsions presented the potential to reduce the mycelial growth of P. digitatum (100 % for nanoemulsion with 2 % WTEO and 80.5 % to 2 % CWTEO) up to 150 days of storage. A nanoemulsion containing 2 % WTEO was applied to orange fruits, and its antifungal potential was evaluated in vivo. This nanoemulsion was able to reduce the incidence of rot caused by P. digitatum in oranges, demonstrating their potential for application as an alternative to synthetic fungicides to reduce postharvest losses in citrus fruits.