Influence of Yeast Strain, pH, and Temperature on Degradation of Fumaric Acid in Grape Juice Fermentation

Abstract

A white grape juice, <i>Vitis vinifera</i> L., `Sultana9, with and without fumaric acid added at 3 g/1 was fermented at 15 and 25°C by three commercial wine yeasts, with initial juice pH adjusted to 3.0, 3.6, and 4.2. Fumaric acid in the wine was measured spectrophotometrically. Initial pH markedly influenced the amount of fumaric acid degraded. Combined results for the yeast strains and fermentation temperatures indicated that fumaric acid degradation was 78% for initial pH 3.0, 63% for pH 3.6, and 28% for pH 4.2. Yeast strain on average, did not influence fumaric acid degradation. Degradation was consistently greater at 25°C than at 15°C, though not to statistical significance. With a different variety of grape juice (<i>Vitis vinifera</i> L., `Rhine Riesling9) initial pH (pH 3.05) unadjusted, the yeast (A.W.R.I. No. 729) degraded 88% of added fumaric acid (3.0 g/1), and the resultant wine (pH 3.41) was similar in pH to control wine made without added fumaric acid. The results indicated that fumaric acid should not be added to grape juice prior to yeast alcoholic fermentation by the commercial wine yeast strains tested, <i>Saccharomyces cerevisiae</i> H. strains A.W.R.I. No. 138, No. 727 (U.C.D. No. 522), and No. 729.