Effect of Grape Skins on the Sulfite Binding Efficiency of Three SO₂-Acceptors in the Wines

Studies on the Use of SO₂ in Wine-making XIV

Abstract

The effect of fermentation on skins, a usual method for red wine-making, on the sulfite binding efficiency of three SO₂-acceptors, i.e. acetaldehyde, pyruvate and α-ketoglutarate, were examined with special reference to the effects of free-SO₂ content, pH value and temperature of the wines. The following results were obtained. (1) Sulfite binding efficiency of three SO₂-acceptors was decreased obviously in the wines fermented on skins. (2) The sulfite-binding efficiency increased remarkably in wines containing higher level of free-SO₂ and of lower temperature, while it was not significantly affected by a change in pH range. (3) The level of bound-SO₂ in the wines obtained by fermentation on skins (EL) estimated on the basis of the amounts of three SO₂-acceptors found in wines, were always lower than the actual level of bound-SO₂ (AL) determined. Consequently, the EL was able to account for 73 to 87% of AL in terms of three SO₂-acceptors. (4) The EL of the wines obtained by fermentation on skins was very higher than the AL in the previous papers, the difference between the EL and the AL probably results from the over-estimation of the sulfite binding efficiency of three SO₂-acceptors.