Effect of high pressure carbon dioxide on the properties of water soluble pectin in peach juice

To better understand the pectin and its role in precipitation formation in peach juice induced by high pressure carbon dioxide (HPCD) in a previous study, demethoxylation, molecular weight distribution (MWD), ξ-potential, rheological properties and nanostructure of water soluble pectin (WSP) from peach juice treated by combining HPCD with pectin methylesterase (PME) were studied. The MWD, ξ-potential and nanostructure of WSP were not changed, whereas demethoxylation reaction was stimulated by HPCD. Significant decreases in degree of methoxylation (DM) and apparent viscosity of WSP were obtained with PME action after moderate heat treatment (MHT) at 55 °C, and the nanostructure image of WSP exhibited more aggregation than control and HPCD alone. PME in buffer system was susceptible to HPCD, whereas it in juice was difficult to be inactivated by HPCD. It was deduced that the properties and structure of pectin could be significantly changed with PME action in peach juice after HPCD. The apparent viscosity of WSP in peach juice could be decreased due to demethoxylation reaction catalyzed by PME in HPCD-treated juice, resulting in the aggregation of WSP, and finally contributing to accelerate the formation of precipitation in peach juice.