Sour Grapes, Indeed! Malic Acid Increases in Certain Vitis spp. during Maturation
Elizabeth Burzynski,* Elizabeth Brown, and Gavin Sacks
*Cornell University, 222 Summerhill Dr Apt 2, Ithaca, NY 14850 (firstname.lastname@example.org)
Wild Vitis and their interspecific hybrids have very high malic acid concentrations (10 g/kg or more), even at late harvest dates and high soluble solids (>20 Brix). The behavior of malic acid in non-vinifera Vitis spp. during berry maturation would be of interest to grape breeding programs and viticulturalists, but to our knowledge has not been reported. Over a two-year study, multiple accessions of V. riparia and V. cinerea were collected from the USDA ARS Cold Hardy Grape Germplasm Collection (Geneva, NY) and V. vinifera and interspecific hybrid grapes were collected from nearby commercial vineyards. Sampling was performed at three to four time points from preveraison to typical commercial sugar maturity (>20 Brix). We observed no significant difference in malic acid among riparia, vinifera, or interspecific hybrids preveraison; however, malic acid (on a g per berry basis) decreased more slowly in riparia than in vinifera, with intermediate degradation rates observed in interspecific hybrids. In some riparia accessions, we observed no significant change in malic acid per berry between the preveraison maximum and harvest. More surprisingly, malic acid increased in cinerea accessions during berry ripening. These findings suggest that high levels of malic acid in wild Vitis and interspecific hybrids than in vinifera result from much lower rates of malic acid degradation and/or continued malic acid synthesis during ripening.
Funding Support: USDA-NIFA SCRI 2011-51181-30635 and the Federal Formula Funds Initiative Project NYG-623448