Hydrothermal Hydrolysis of Hesperidin Into More Valuable Compounds Under Supercritical Carbon Dioxide Condition

Synergistic effects of utilizing subcritical water and supercritical carbon dioxide were investigated for the hydrolysis of hesperidin into more valuable compounds at a pressure range of 10-25 MPa and temperature of 110-140 degrees C. The effect of operating conditions such as pressure, temperature, reaction time, and addition of cosolvent such as ethanol were found to affect the hydrolysis rate. Higher yields were obtained at higher carbon dioxide pressure owing to an increase in formation of carbonic acid. Moreover, the rate of reaction was also found to increase with increasing temperature, obtaining higher yields of the main products, hesperetin-beta-glucoside and hesperetin. Addition of ethanol as a cosolvent could increase solubility of hesperidin, however, it inhibited the reaction and formation of carbonic acid. At the maximum temperature of 140 degrees C and pressure of 25 MPa investigated in this work, the highest concentration of hesperetin-beta-glucoside of 4.2 mol/L was obtained in a reaction time of 2 h, whereas for hesperetin the highest was 6.9 mol/L obtained in 3 h. Among the hydrolysis methods investigated, the proposed method was the most selective toward formation of the target compounds.