Kinetic assessment on the autohydrolysis of pectin-rich by-products

Abstract

Fractionation in aqueous media is an environmentally friendly technology suitable for obtaining oligomeric products from pectins and hemicelluloses. Sugar beet pulp (SBP) samples were subjected to aqueous processing under non-isothermal conditions to reach maximal temperatures in the range 140–200 °C, in order to cause the conversion of pectins into soluble compounds of lower molecular weight with potential applications as prebiotic ingredients. Mixtures of arabinooligosaccharides, oligogalacturonides and oligomers made up of other structural units were obtained by non-isothermal processing of SBP in aqueous media. Kinetic models suitable for reproducing and predicting compositional data of reaction liquors as a function of the operational conditions were developed. According to the model predictions, the maximum arabinooligosaccharides yield (15.7 g/100 g SBP) corresponded to a treatment carried out to achieve 171.5 °C. Alternatively, the maximum oliogogalacturonide yield (14.1 g/100 g SBP) was predicted for a treatment performed to achieve 158.2 °C. In both cases, the overall yield of oligomeric saccharides was near to 30 g/100 g dry SBP, whereas the oligosaccharide mixture of higher purity was obtained operating at 158.2 °C. Depending on the operational conditions, SBP processing in aqueous media yielded oligomers with different compositional profiles. The developed models were suitable for a quantitative interpretation of experimental data, and provided key information for both design calculations and economic evaluation.