Pectooligosaccharides rich in galacturonic acid produced from Orange Processing Waste by autohydrolysis: Process optimization and kinetic analysis

Abstract

Pectooligosaccharides (POS) are notorious for their prebiotics and elicitor activities. In this work, we have optimized the autohydrolysis of Orange Processing Waste (OPW) to obtain POS fractions via a Taguchi approach, maximizing homogalacturonan oligosaccharides yield by considering several process variables: particle diameter, stirring speed, liquid-solid ratio and time, determining that only time had a significant effect in the studied range. 19.38 % w/w POS yield from OPW was obtained in optima conditions. After ensuring no limitation due to mass transfer, the kinetic analysis assumed that homogalacturonan was converted into high, medium and low molecular weight oligosaccharides, and galacturonic acid. Moreover, we considered that there is one pseudo-homogeneous reaction type combined with three irreversible, elemental, of pseudo first global order (first order with respect to the reagent which is hydrolysed) reactions in series. The model successfully reproduced experimental data at constant temperature (150 °C–180 °C) and pH (3.73).