Tartaric acid recovery from winery lees using cation exchange resin: Optimization by Response Surface Methodology

A crucial first step in developing a novel cost-effective and environment-friendly process for recoveringtartaric acid and bioactive polyphenolic compounds from wine lees involves tartrates dissolution by mildmeans, aiming to maximize tartaric acid recovery, while minimizing the concentration of undesirablepotassium. Such a processing step, using cation exchange resin, has been systematically assessed toobtain a set of near-optimum values of the key variables (i.e. pH, water dosage and cation exchange resindosage). An experimental design was carried out based on Central Composite Design (CCD) withResponse Surface Methodology (RSM) to evaluate the effects of process parameters and their interactiontowards the attainment of optimum conditions. All three variables considered were found to be significant;however, the most influential factor for maximum tartaric acid concentration was the volume ofadded water, whereas for potassium removal the cation exchange resin dosage. A quadratic model wasdeveloped that fitted well to the experimental data confirmed by the high R2 values, greater than 0.98.A set of optimum values of the three main variables was determined to be pH = 3.0, water dosage10 ml/g dry lees and resin dosage 3.5 g/g dry lees. Under these optimum conditions, the predicted tartaricacid and potassium concentration were 43,143 ppm and 178 ppm, respectively, which correspond to74.9% tartaric acid recovery and 98.8% potassium removal. Furthermore, the corresponding experimentalvalues, from the validation experiment, fitted well to these predictions. This work clearly shows that therecovery of tartaric acid from wine lees can be achieved using cation exchange resin, under mild conditions(ambient temperature) avoiding the waste calcium sulfate sludge of the conventional process.