RT Journal Article SR Electronic T1 Formation of Ethyl Esters of Tartaric Acid During Wine Aging: Chemical and Sensory Effects JF American Journal of Enology and Viticulture JO Am J Enol Vitic. FD American Society for Enology and Viticulture SP 118 OP 124 DO 10.5344/ajev.1985.36.2.118 VO 36 IS 2 A1 Theodore L. Edwards A1 Vernon L. Singleton A1 Roger Boulton YR 1985 UL http://www.ajevonline.org/content/36/2/118.abstract AB Esterification of tartaric acid with ethanol was determined by ferric hydroxamate colorimetry at frequent intervals for up to 38 weeks in wine-like model systems. The study covered a range of pH from 2.97 to 4.07, ethanol content of 8% to 18% (v/v), tartaric acid contents of 4 to 10 g/L, and temperatures between 0° and 50°C. Ethyl acid tartrate was synthesized and shown to have a pKa of 3.12. The chemical and sensory effects of the conversion of a portion of the tartaric acid to its ethyl esters were evaluated. The production of ethyl acid tartrate in aged wines is sufficient to decrease the sensory acidity and apparent harshness and thus have a mellowing effect. Addition of ethyl acid tartrate or diethyl tartrate to wine near or above levels which could be expected to result from aging did not produce a significant sensory effect; therefore, these compounds did not contribute directly to flavor. A kinetic model was developed and used to interpret the experimental results. Rate constants for the formation and hydrolysis reactions were deduced. The overall reaction was slow to reach equilibrium under typical wine storage conditions, but easily accounts for the formation of several hundred milligrams of ethyl acid tartrate per liter during wine aging.