S23 - Session P1 - Post-harvest ethanol treatment to increase anthocyanins content in red wine grapes

Authors: Margherita Modesti, Giorgio Manganelli, Brunella Ceccantoni, Serena Ferri, Fabio Mencarelli *, Andrea Bellincontro

Red wine grapes are generally evaluated mainly for their content in polyphenols and anthocyanins. Unfortunately, in some conditions (weather, latitude, and temperature) the concentration of these compounds at the harvest time is not at the right level for reaching a high-quality wine. Ethanol is a plant secondary volatile metabolite and its application in post-harvest has been proposed as an approach to reduce post-harvest decay and to increase the production of other secondary metabolites such as volatiles and polyphenols. In fact, ethanol exposition can induce oxidative stress leading, in turn, to antioxidant metabolic responses. In the present study, red wine grapes ( Vitis Vinifera L. cv Aglianico) were exposed, in postharvest time, to different doses of gaseous ethanol (namely 2.5, 5, or 10 ml of 99% ethanol) in a 20 L sealed barrier polyethylene bag for 12, 24 or 36 h. As response of the treatments, ethanol increased sugar concentration, malic acid, free amino nitrogen, and, most important, anthocyanins content in musts. The increase of anthocyanins was observed after 12 h of treatment whatever the concentration was. The effect of the gaseous applications was also investigated in terms of metabolic response, by testing several enzyme activities strictly related to the fermentative pathway (ADH, PDC) as well as to that of lipoxygenase (LOX, HPL). Obtained results suggest that 12 h of ethanol gaseous postharvest treatment on wine grapes could be a valid solution to improve the anthocyanins fraction of red wine grapes when the quality is not as good as expected.