RG- І pectin affects the physicochemical properties and digestibility of potato starch

Abstract

The effects RG-І pectin (0.5, 1, 2, 5 and 10%, w/w) on the gelatinization behaviour, gel structure and digestibility of potato starch were characterized by means of rapid viscosity analysis (RVA), rheometry, scanning electron microscopy (SEM) and in vitro digestion. Results indicated that the addition of RG-I pectin significantly decreased the peak and breakdown viscosity and prolonged the pasting temperature of potato starch, but increased the setback viscosity. Meanwhile, the swelling power and amylose leaching of starch granules were restrained because of RG-I pectin adsorption on the starch granules surface. The presence of RG-I pectin also decreased the G’ values of potato starch gel but increased the tan δ values (especially for 1%), indicating that RG-І pectin decreased the 3D network formation of potato starch gel. The microstructure analysis indicated that RG-I pectin decreased the formation of the gel structure, which might place constraints on the relative amylose concentration in the continuous phase. The addition of RG-I pectin also reduced the rapidly digestible starch (RDS) content and increased the slowly digestible starch (SDS) content, while no significant differences of resistant starch (RS) content was observed. Those results indicated that RG-I pectin could affect the physicochemical properties of potato starch and modulate its digestibility and might be a potential option for producing starchy food with lower digestibility.