Optimization of the extraction of chlorophylls in green beans (Phaseolus vulgaris L.) by N,N-dimethylformamide using response surface methodology

A method for extracting and determining chlorophyll pigments (chlorophyll a and b) in green beans (Phaseolus vulgaris L.) was developed. The procedure was based on the solvent extraction of pigments in vegetable samples using N,N-dimethylformamide as the extractant. Optimal conditions for extraction were determined by experimental design using response surface methodology. Central composite design “2n+star” was used in order to optimize the following solvent extraction parameters: extraction time, homogenization time and number of extractions. The results suggest that the number of extractions is statistically the most significant factor and that the optimum values for the variables are 90 min extraction time, 1 min homogenization time and number of extractions 5. This work confirms the advantages of experimental design compared to traditional optimization strategies because it allows a large number of factors to be screened simultaneously, provides less ambiguous data and helps to visualize relationships between responses and factor levels. Pigments were determined using UV–vis spectrophotometry at 647 and 664 nm. The chlorophyll content was analyzed in three green-bean cultivars: Donna, Negrital and Emerite.