Pectin extraction from pomegranate peels with citric acid

Pectins were extracted from pomegranate peels with citric acid, according to a central composite design with three variables: pH (2-4), temperature (70-90 degrees C), and extraction time (40-150 min). Fourier transform infrared (FTIR) spectroscopy was used to follow changes in material composition during the main steps of pectin extraction, and also to determine the degree of methyl esterification and galacturonic acid content of pectins produced under different conditions. Harsh conditions enhanced the extraction yield and the galacturonic acid contents, but decreased the degree of methoxylation. The optimum extraction conditions, defined as those predicted to result in a yield of galacturonic acid higher than 8 g/100g while keeping a minimum degree of methoxylation of 54% were: 88 degrees C, 120 min, pH 2.5. Close agreement was found between experimental and predicted values at the extraction conditions defined as optimum. (C) 2016 Elsevier B.V. All rights reserved.