Optimization of the extraction of roselle (Hibiscus sabdariffa L.) dried calyxes' juice

The objective of the work consisted in modeling and optimizing the juice extraction physicochemical characteristics from Hibiscus sabdariffa L., in order to be able to put forward its qualities. This was done using response surface methodology (RSM). The models obtained at 60°C using Doehlert experimental design were of second order with interaction. The validation of those models used the coefficient of correlation R2 (0.998 and 0.994 respectively for turbidity and extract), the absolute average deviation (AAD) (0.068 and 0.056 respectively for turbidity and extract), the bias factor (0.95 and 0.98 respectively for turbidity and extract) and the exactitude factor (1.08 and 1.05 respectively for turbidity and extract). In this study, factors as calyxes/water ratio and maceration time which influenced significantly on juice turbidity and extract was modeled and optimized. The calyxes/water ratio contributions were 34% and 43% respectively for turbidity and extract while, the maceration time contributions were 23% and 10% respectively for turbidity and extract. At 60 °C of extraction temperature, we were able to have turbidity up to 307.22 NTU and extract up to 12 °B. When optimizing the responses, it was possible to have juices with less turbidity (|[asghar_aw]| 200 NTU) and high extract (? 6 °B).