The ratio of the areas of isosteviol (ISV) to dihydroisosteviol (DHISV) as a function of the reaction time at different reaction temperatures (A: 60 °C; B: 80 °C; C: 100 °C) and H2SO4 concentrations (-♢- 1%, -□- 2.5%, -△- 5% and -×- 10%). The dotted line marks the ratio of 1.76, the theoretical point of 100% hydrolysis of the applied concentration of 0.161 mM steviol equivalents.