EFFECT OF UV-C TREATMENT ON DEGRADATIVE ENZYMATIC ACTIVITIES IN MINIMALLY PROCESSED GALIA MELON

The effect of exposure of minimally processed “Galia” melon (Cucumis melo L. var. reticulatus) to ultraviolet-C (UV-C, 254 nm, 0.04 kJ s-1 m-2) radiation for different times (30, 60, 120 s) on degradative enzymatic activities (polyphenol oxidase, peroxidase, pectin methylesterase and polygalacturonase) and quality parameters (firmness, colour) during storage at 5 °C was investigated. Enzymatic activities in samples washed with water and treated with UV-C radiation resulted similar to samples washed with 100 mg L-1 NaOCl and significantly lower than untreated samples, especially after 7 days of storage at 5 °C. Wounding induced a defense mechanism leading to increased activity of polyphenol oxidase, peroxidase and polygalacturonase throughout the storage period, both in UV-C treated and untreated samples. Fruit exposed to UV-C for 30 s had the lowest pectin methylesterase activity above all at the end of storage period. Tissue softening was noticed in all samples although those treated with UV-C light resulted 7 to 12% firmer than untreated ones. The lowest perceptible colour variation, expressed as E, was in samples exposed to 120 s radiation (E=8.58), while the highest value was noticed in untreated sample (E=11.06). Post-cut UV-C fruit treatment was effective in extending the shelf-life of minimally processed “Galia” melon.