Comprehensive chemical study of the acidification of musts in Sherry area with calcium sulphate and tartaric acid

¹ Department of Chemical Engineering and Food Technology, Faculty of Sciences. University of Cadiz, 11510 Puerto Real, Spain
² Department of Analytical Chemistry, Faculty of Sciences, University of Cadiz, 11510 Puerto Real, Spain
³ Bodegas González-Byass, C/Manuel María González, 12, 11403 Jerez de la Frontera, Spain
⁴ Grupo Estévez S.A. Carretera Nacional IV. Km 640, 11408 Jerez de la Frontera, Spain
⁵ Fundación Jerez, Control y Certificación, Avda, Alcalde Álvaro Domecq, 2, 11402 Jerez de la Frontera, Spain

^a e-mail: juangomez.benitez@uca.es

Abstract

Calcium sulphate addition has traditionally been used in Sherry winemaking to reduce the necessary dose of tartaric acid. It is not easy to predict the final pH of a mixed tartaric acid and calcium sulphate addition and to determine the necessary doses to reach the final pH required by the winemaker because there are several interrelated chemical equilibra implied (tartaric acid dissociation, calcium tartrate and potassium bitartrate precipitation etc.). To predict the effect on pH, several chemical modeling approaches have been described in the literature. It is noteworthy to mention the simplified model where the acidity of wine is considered to be due to a monoprotic acid. In this work the prediction of pH at industrial scale was confirmed and its practical application was facilitated by linear regression lines prepared with pilot scale data. Additionally, sensory analysis of wines acidified with calcium sulphate and tartaric acid alone and mixed indicates that there are great differences among them in taste and that mixed acidification is the preferred by the tasters. That confirms the good comprehension of the chemical equilibria involved in this practice and supply very useful information for its final approval in OIV.