However, it was also found that increasing the pH also increased the epimerization rate ( Supplemental Fig. S5). Therefore a pH of 8.5 was selected as a compromise. The results also showed that 40 mL of extraction solvent and an extraction time of 30 min were sufficient. Longer extraction time resulted in higher epimerization rate. Regarding the drying temperature (investigated in the range from 40 to 60 °C), less epimerization occurred when a temperature of 40 °C was applied; this temperature was therefore selected in the optimised procedure.