Optimization of the subcritical water extraction of phenolic antioxidants from Crocus sativus petals of saffron industry residues: Box-Behnken design and principal component analysis

Abstract

Subcritical water extraction was investigated as a green technology for the extraction of phenolic compounds from Crocus sativus petals. A Box-Behnken design was utilized to determine the optimal extraction conditions. Extraction temperature (120–160 °C), extraction time (20–60 min) and water to solid (W/S) ratio (20–40 mL/g) were considered as the variables for the extraction of phenolic compounds. A second order polynomial model was fitted to each response and the regression coefficients were determined using least square methodology. There was a good correspondence between the experimental data and their predicted counterparts. The optimum conditions of extraction were estimated to be W/S ratio of 36 mL/g, temperature of 159 °C and time of 54 min. Extraction using these optimized conditions achieved the best TPC (1616 mg/100 g), TFC (239 mg/100 g), %DPPHsc (86.05%) and FRAP value (5.1 mM). Principal components analysis (PCA) allowed a better understanding of interactions between properties of extracted phenolic antioxidants. Application of subcritical water was shown to be a practical technique to extract the phenolic compounds of saffron petals as an underutilized bulk agro-waste. The higher phenolic antioxidants obtained in extractions carried out by this technique is of major interest from an industrial point of view, since solvent amounts were reduced and extraction times shortened. Thus, the application of this emerging technology for extraction uses and low-cost raw materials is an economical alternative to conventional extraction methods according to industry demands and a sustainable development.