Response surface methodology of subcritical water-reactive extraction of gingerol to shogaol ginger dregs through ultraviolet light pretreatment

The increase of shogaol production through reactive extraction of subcritical water depends on the stages of the pretreatment process in destroying the cellular cells of ginger pulp. Pretreatment using ultraviolet B (UVB) is predicted to be able to damage cellular cell walls and outer cell membranes (plasmalemma). In addition, to initiate the degradation of gingerols to shogaols, the reaction conversion and selectivity of shogaols are increased. This study aimed to examine the optimum process conditions for the subcritical water-reactive extraction of gingerol to shogaol from the ginger pulp by utilizing UVB pretreatment: reactive extraction temperature (110 – 130oC), ratio solvent/feed (22:1 – 32:1 b/b), and time (10 – 30 minutes). The extract of shogaol in solvent was separated from the raffinate with a separator funnel and analysed using HPLC-MS. Interpretation of experimental data to optimize the reactive extraction process used the Response Surface Methodology (RSM). The study results show that at 120°C, solvent:inlet ratio 27:1 for 20 minutes through ultraviolet B-light pretreatment for 10 minutes, the yield of shogaol increased from 177 µg/L (without UV) to 18646 µg/L. Moreover, the RSM model was very good at predicting shogaol acquisition responses with a determination coefficient of R2 to be 0.8554. The optimum condition for reactive extraction through UV-B light pretreatment was reached at a temperature of 121.46°C and an inlet solvent ratio of 27.96 at 18.36 minutes, with a shogaol concentration of 18567.1 µg /L.