Effects of Pectin on the Pasting, Rheological, and Textural Properties of Lotus Root Starch

摘要

To determine the effects of hydrocolloids on starch properties, high-methoxyl pectin (HMP), and low-methoxyl pectin (LMP) are mixed with lotus root starch (LRS). Changes in pasting, rheological, and textural properties, and microstructure of LRS composites are analyzed. LMP increases final viscosity, peak viscosity, breakdown viscosity, retrogradation value, and peak time of starch paste. HMP increases the peak time, but it decreases all other four pasting parameters. LMP increases shearing stress of LRS paste. The shearing stress of LRS paste is proportional to LMP concentration. With increasing consistency coefficient K, the flow behavior index n decreases. Opposite results are observed in HMP. In the LRS/HMP and LRS/LMP, G and G are positively correlated with LMP content, but these are negatively correlated with HMP. The minimum tan is achieved when LRS:LMP=8:2, thereby indicating the strongest elasticity features. HMP can well inhibit short-term retrogradation of LRS. Pectin decreases LRS hardness but increases cohesiveness, thereby forming a softer gel. Variations of adhesiveness and springiness are related with pectin type. According to SEM observation, the involvement of LMP destroys the original structure of LRS and forms a stable network structure, which is rare in the LRS/HMP system.