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Carboxylic acid-catalysed hydrolysis of polygalacturonic acid in subcritical water media

Abstract:

Pectin is comprised of a heterogeneous group of polymers, including linear homogalacturonan. Pectic-oligosaccharides obtained from pectin hydrolysis have beneficial health effects. In this study, linear chain polygalacturonic acid was used as a pectic model system. The use of di- or tri-carboxylic acids as catalyst under subcritical water conditions was investigated as an eco-friendly alternative to hydrolyze polygalacturonic acid into oligogalacturonides. The hydrolysis was carried out in a batch mode at 125 and 135 °C/100 bar and reaction times of 10–120 min. Hydrolysates were characterized by HILIC-ELSD. Polygalacturonic acid hydrolysis pattern led to poly/oligogalacturonic acid intermediates (8−14 DP) that were subsequently hydrolysed to oligogalacturonides (2−7 DP). The reaction mechanism involved parallel and consecutive reactions. Temperature had a significant (p < 0.05) effect on polygalacturonic acid breakdown. The highest yield of oligogalacturonides was 41 % at 135 °C/100 bar/30 min. Experimental results were used to establish a possible mechanism and model to describe the hydrolysis kinetics.