Effect of Hormonization Treatment on Yield Quantity and Quality, Contents of Biologically Active Compounds, and Antioxidant Activity in ‘Einset Seedless’ Grapevine Fruits and Raisins

In this study, we determined the effect of hormonization treatment on yield quantity and quality, content of biologically active compounds, and antioxidant activity in fruits and raisins of ‘Einset Seedless’ grapevine. Field studies were conducted in 2017 at Nobilis Vineyard (50°39′ N; 21°34′ E) in the Sandomierz Upland. Analytical studies were carried out in the Laboratory of the University of Life Sciences in Lublin. Hormonized fruits and raisins, which were dried at 40 °C in a food dryer for 7 days, were the experimental material. It was shown that the application of the hormonization treatment had a significant effect on yield size and quality. The hormonization treatment and the form of plant material analyzed had a significant effect on the content of biologically active compounds and the antioxidant activity in ‘Einset Seedless’ grapevine fruits and raisins. The concentration of applied gibberellic acid had a significant effect on the levels of acidity, content of anthocyanins, and antioxidant activity determined with the FRAP and DPPH methods. The application of the multivariate analysis technique showed that, in the fresh fruits and raisins, the level of biologically active compounds and antioxidant activity in the case of the 200 mg∙GA(3)∙L(−1) concentration and in the control combination was similar but differed significantly in the case of the 300 mg∙GA(3)∙L(−1) application.