Equilibrium and Kinetic Parameters for the Sedimentation of Tartaric Salts in Young Wines

Abstract

Abstract. In young wines potassium hydrogen tartrate is always present in supersaturating concentration and crystallizes spontaneously. The aim of this study is to obtain kinetic parameters, which explain the stability of young wines during the stabilization treatments. The kinetic and equilibrium parameters were evaluated and discussed. The heating factor has a decisive infl uence on the reaction rate of potassium hydrogen tartrate precipitation in young wines. An increase of temperature leads to a decrease in effi ciency of stabilization process and to an enhancement of the activation energy of the system. According to the obtained experimental results, the optimal regime for production and stabilization of young wines has been established.Keywords: kinetic parameters, young wines, crystalline stabilization, Arrhenius plots. IntroductionThe presence of tartaric salts, potassium hydrogen tartrate (KHT) and calcium tartrate (CaT) is one of the main causes of wines instability. The wine differs in the retention capacity for tartaric salts in solution. If the holding capacity is exceeded, these salts will precipitate, resulting in the formation of tartrate casse or tartaric precipitation [1]. Generally, the solubility of potassium hydrogen tartrate primarily depends on the alcohol content, the value of pH, the temperature of the wine, the presence of colloids and the interactive effects of various cations and anions. In young wines, KHT is always present in supersaturating concentrations and crystallizes spontaneously [2].Nowadays, several treatments are used prior to wine bottling in order to prevent the precipitation of tartaric salts. Physical treatments consists in promoting the crystallization by cooling the wine to -4°C and subsequent removal of tartaric salts by fi ltration or elimination of the potassium and tartaric ions by electro-dialysis or by the use of ionexchange resins [3,4]. The used for the treatment of young wines cooling techniques have found a commercial application. These techniques are characterized by long term (weeks), the wine conservation being carried out at temperature below freezing, to encourage the tartrates to crystallize and precipitate out of the wine [5].The precipitation of KHT in wine follows a second-order kinetics reaction between the bitartrate ion (HT