The use of cation exchange resins for wine acidity adjustment: Optimization of the process and the effects on tartrate formation and oxidative stability
Abstract
Acidity adjustments are key to microbial control, sensory quality and wine longevity. Acidification with cation exchange resins -in acid cycle- offers the possibility to reduce the pH by exchanging wine cations, such as potassium (K+), for hydrogen ions (H+). During the exchange process, the removal of potassium and calcium ions contributes to limiting the formation of tartrate salts, thus offering an alternative solution to conventional methods for tartrate stability. Moreover, the reduction of wine pH and the removal of metals catalyzers (e.g. iron) could positively impact the wine’s oxidative stability. Therefore, the aims of this work were (a) to optimize the ion exchange process by testing different volumes and concentrations of sulfuric acid (H2SO4) during the acid cycle, (b) evaluate the effects of the ion exchange process on the formation of tartrate salts, and (c) analyze the oxidative stability of the treated wines. The study involved a series of laboratory and commercial scale trials in which the chemical composition, tartrate and oxidative stability of the samples were investigated. In brief, the use of a 20% H2SO4 solution for the activation of the resins was equally effective in lowering the wine’s pH than a 50% H2SO4 solution. Correspondingly, 2.5 volumes of H2SO4 solution were enough to activate 10 volumes of resin. The outcomes of using cation exchange resins were wines with significantly lower pH (e.g. 33.5% reduction), higher titratable acidity (e.g. 31% rise), higher concentration of free sulfur dioxide (e.g. 56% increase), less cations such as potassium, calcium, iron, copper (e.g. 57 to 99 % drop), etc. Regarding tartrate stability, white and red wine samples were subjected to cation exchange treatments, and the resulting wines were blended back with the untreated wines in different proportions ranging from 0 to 100%. Wine tartrate stability was achieved by blending untreated wines with approximately 20% of cation exchange treated samples (by volume). Blends with higher volumes of cation exchange treated wines were significantly more stable but less appreciated from a sensory point of view. Finally, with regards to wine oxidation, the treatments caused a positive effect on the oxidative stability of the blends produced.
Acknowledgements: Fondecyt grant Nº 1150725
Issue: Macrowine 2016
Type: Poster
Authors
*Universidad de Talca