Effect of phenolic aqueous extracts obtained from soy flour and microperforated films on fungal resistance of 'Ambrunés' sweet cherries during postharvest storage

The use of controlled or modified atmosphere packaging has been reported to be effective in sweet cherry storage. However, it is not enough to prevent the development of postharvest diseases caused mainly by molds and yeast during long periods of storage. Recently, numerous works have described antioxidant and antimicrobial activity for phenolic compounds. The aim of the present study was to evaluate the antimicrobial activity of phenolic compounds from soy flour against fungal pathogens with the aim to be used as natural biocontrol agents during the storage of sweet cherry. The antimicrobial activity of phenolic compounds was tested in vitro against selected yeasts and molds causing decay. The phenolic extract was also tested on sweet cherries previously disinfected with sodium hypochlorite and then treated with 500 mg L-1 phenolic aqueous extracts. Fruit were packaged in polypropylene trays and sealed with different microperforated films (3 (MF1), and 5 (MF5) holes). As controls, treated or untreated fruits with phenolic extracts were packaged in (BOPP) macroperforated film with six holes (ø=9 mm). All batches were stored at 1°C and RH of 95% for up to 35 days. After 0, 7, 14, 21, 28 and 35 storage days microbial analyses of molds and yeasts were carried out. Phenolic compounds from soy flour presented a broader inhibitory spectrum. Concentration of 1.5 mg L-1 showed a 50% of inhibition of Cryptococcus spp., Torulaspora spp., Rhodotorula spp. and 93% against Aureobasidium pullulans, whereas much higher concentration were necessary to reduce the growth of Cladosporium uredinicola, Penicillium glabrum, Botrytis cinerea and Monilia laxa. In addition, the application of phenolic aqueous extracts on sweet cherries, alone or in combination with microperforated films, improved their shelf life during the storage.