Performance evaluation of volatile organic compounds by antagonistic yeasts immobilized on hydrogel spheres against gray, green and blue postharvest decays.

Wickerhamomyces anomalus, Metschnikowia pulcherrima, Aureobasidium pullulans and Saccharomyces cerevisiae yeasts were tested for their ability to survive and synthesize antifungal volatile organic compounds (VOCs) both in vitro and in vivo conditions when immobilized on commercial hydrogel spheres. The results showed a good survival of all yeasts on hydrogel spheres up to 10 days of incubation. Moreover, VOCs produced in vitro by tested yeasts inhibited Botrytis cinerea, Penicillium digitatum and P. italicum radial growth and conidial germination, with the highest antagonistic activity reported for W. anomalus and A. pullulans strains. Experimental in vivo trials performed on strawberry and mandarin fruits proved the ability of VOCs to reduce significantly postharvest decays on artificially wounded tissues. Comprehensively, the best efficacy was detected for W. anomalus, which totally inhibited gray mold decay on strawberry fruits and significantly reduced green mold infections on mandarin fruits. On the other hand, blue mold decay on mandarin fruits was more effectively managed by A. pullulans VOCs. Accordingly, hydrogel spheres used as a support for VOC-generating yeasts could open a new way for the employment of this polymeric material as a bio-emitter in postharvest packaging.