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

Abstract

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°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°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.