Control of postharvest table grape sour rot development during shelf-life after cold ozonation treatment

In this work the development of table grape sour rot, a disease sustained by a consortium of non-Saccharomyces yeasts (NSY) and acetic acid bacteria (AAB), was observed under postharvest conditions inoculating wounded berries with 8 NSY strains, or 7 AAB, or their combinations (56). Candida zemplinina CBS 9494 (Cz) and Acetobacter syzygii LMG 21419 (As) produced the highest percentage of rotten berries (100%) after 6 days at 25 °C. Subsequently, the efficacy of low doses of gaseous ozone (2.14 mg m-3) was evaluated in wounded berries inoculated with this simplified As-Cz microbial consortium after ten days at 4 °C. At the end of cold storage, no sample showed sour rot symptoms, although ozonation mainly affected the As viability. In order to simulate sale conditions, all samples were additionally stored at 25°C for 12 days. After this period, the sour rot index of inoculated As-Cz berries previously cold-stored under ozone or air accounted for 22.6 ± 3.7% and 66.7 ± 4.5%, respectively. Inoculated rotten berries showed a slight reduction in monosaccharide content and the different increases in concentration of acetic acid, gluconic acid, ethanol and glycerol. Microbiological analyses of sound and rotten berries revealed, in addition to As and Cz, the occurrence of 15 new strains potentially responsible for sour rot development and mainly belonging to Gluconobacter albidus and Hanseniaspora uvarum. In this work we demonstrated that cold ozonation was useful to extend the shelf-life of cold stored table grapes even when, at the end of treatment, they were further stored at room temperature.