Modeling and optimization of pilot-scale subcritical water extraction on Zingiber zerumbet by central composite design

Zingiber zerumbet (Z. zerumbet) or locally called `lempoyang' is one of the ginger species extensively cultivated and utilized in the Southeast Asia region. In order to extract valuable ingredients from Z. zerumbet, a green and non-toxic extraction process is implemented namely subcritical water extraction (SWE). Modeling and optimization of SWE of Z. zerumbet are performed using the central composite design (CCD) by 20 runs with 6 repetitions at the center point. The independent variables investigated in this research are temperature (130-170 degrees C), time of extraction (20-40 minutes) and solid to solvent ratio (20-40 ml/g) that focused to identify the optimized process parameters for zerumbone concentration, antioxidant activity, and yield of extracts. All independent variables researched were analyzed to be significant as the p-value for zerumbone concentration, antioxidant activity and yield are 0.0001, which are less than 0.05 for a model to be significant. The optimum process parameters for all responses of Z. zerumbet extract are at 170 degrees C, 20 minutes and 20 ml/g. This optimum condition was validated and the correlation between predicted and experimental values was within 95% which indicated the range of variables selected was valid. Thus, the outcome from this research may be beneficial on subcritical water extraction of ginger species especially Z. zerumbet.