Influence of pectin esterification degree on the characteristics of indica rice starch-pectin composite gels

The application of natural indica rice starch in the food industry is limited because of its low gelatinization stability and high tendency to retrogradation. The present study aimed to improve the characteristics of starch gels by adding pectins with various degrees of esterification (DEs) and explored the structure-function relationship within the starch-pectin composite system.

Low-methoxyl pectin (DE = 38%) inhibited the water absorption, swelling and dissolution of indica rice starch granules, thereby hindering starch gelatinization and leading to a reduction in gelatinization enthalpy (ΔH_G) from 1.45 to 1.33 J g^-1. Increasing the DE from 38% to 73% significantly raised the complex index from 9.36% to 22.25%. High-methoxyl pectin (DE = 73%) increased ΔH_G from 1.45 to 1.69 J g^-1 and short-range order from 0.650 to 0.730. Scanning electron microscopy revealed that high-methoxyl pectin promoted the formation of a more continuous and organized gel network. During storage at 4 °C for 14 days, low-methoxyl pectin significantly reduced the relative crystallinity and free water content through interactions with water and starch molecules, improving the water retention ability of the starch gel and exhibiting stronger inhibition of retrogradation.

The addition of pectin with various DEs could influence the gelatinization, structural and retrogradation characteristics of indica rice starch, and could also improve the quality and storage stability of starch gels, promoting the use of pectin in indica rice starch-based products. © 2025 Society of Chemical Industry.