In this thesis is included examination conducted on table grapes cv. Italia produced under two types of plastic cover used with the purpose to delay harvest day. One plastic cover was experimental, the other was a commercial type presently widely diffused; they differed in transmissivity to the radiometric spectrum. The main aim of work was to compare final changes regarding the main parameters that describe external and internal features of grape quality. Tests that conducted in this work were run to obtain indication about: physical and mechanical traits of cluster and berry; basic berry juice composition; total content of main skin and pulp phenol compounds; skin antioxidant activity. Results indicated that grape physical and mechanical traits and basic berry juice composition changed a very small extent. The parameters most influenced were the berry phenol contents, especially polyphenols and flavonoids: they were higher in grapes produced under the experimental film, likely due to its higher transmissivity to the ultraviolet wavelength range that is known to stimulate phenol biosynthesis.