Malic Acid as a Potential Marker for the Aroma Compounds of “Amarone Wine” Grape Varieties in Withering

Abstract

Amarone is a wine produced from withered grapes of Corvina, Corvinone, and Rondinella. The berry’s water loss in the withering process is combined with the berry senescence thus, significant metabolic changes occur. We report the changes in malic acid, total polyphenols and in aroma compounds of the single Amarone varieties during withering. Grape bunches of the three varieties were withered in a commercial facility and the weight loss (w.l.). was measured to sample grapes for analyses (10, 20, 30, and 50% w.l.). Rondinella grapes lost weight faster than Corvina and Corvinone. Malic acid decreased rapidly in all varieties but, overall, in Rondinella grapes with 20% w.l.; subsequently, malic acid increased. Total polyphenols rose slighty in grapes with 20% w.l. but, then, the content increased more than the concentration effect,. At harvest, the aroma compounds in high concentration that decreased in withering, were 6-methoxy-3-methylbenzofuran, 4-vinylguaiacol, 3,4,5-trimethoxybenzyl alcohol, vomifoliol, and coumaran measured in all varieties, with the highest concentration in Corvinone. In withering, most of the markers showed a peak at 10% and/or 20 w.l. in Rondinella grapes, while in Corvinone the peak was at 20% w.l. as in Corvina grapes, which exhibited also a concentration peak of some compounds at 30% w.l. Thus, not all grape varieties behave in the same way in withering, thus it is necessary that winemaker knows the weight loss (and the time) to reach the best aromatic expression of one variety in order to process it. By matching malic acid trend with aroma compound ones, we assumed malic acid could be an easy tool to monitor the changes on aroma compounds in grape withering.