Effects of Continuous Exposure to Ozone Gas and Electrolyzed Water on the Skin Hardness of Table and Wine Grape Varieties

The effects of continuous exposure to ozone gas (O3, 30 μL/L, 24 h) and immersion in electrolyzed water (EW, 400 mg/L free chlorine, 10 min) on skin hardness of Italia and Muscat Hamburg table grapes, and Merlot and Barbera wine grapes were investigated and compared with those of control treatments (air and deionized water). Skin hardness was instrumentally evaluated via measurements of skin break energy using a puncture test. For all cultivars and density classes, ozone treatment was more effective in increasing skin hardness than EW treatment, although the differences were not always significant. For the same treatment, skin hardening was independent of berry density, and the magnitude of this effect was cultivar-dependent. This skin hardening might positively affect the postharvest life of table grapes. In wine grapes, increases in skin break energy values were related to higher yields and slow extraction kinetics of phenolic compounds during maceration.