Effects of sucrose on the structure formation in high-methoxyl apple pectin systems without acidifier

Abstract

The sucrose effects on the cooling-induced structure formation of acidifier-absent high-methoxyl apple pectin systems were investigated. Three pectin samples with degree of esterification (DE) of 60.6%, 66.1% and 72.4% were applied. At any tested sucrose level (45–65%, w/w), all pectin systems displayed a shear-thinning nature. For a specific pectin, its gelling temperature in cooling as well as the degree of thixotropy, elastic modulus (G′), viscous modulus and equilibrium modulus at ambient temperature increased with sucrose concentration (cs). At a given cs, all above-mentioned parameters decreased with DE. This attested that sucrose favored the structure formation in pectin system, while its effect weakened in the system with a higher DE. The temperature sweep showed that a two-stage process involved in the structure formation in pectin system during cooling from 85 °C to 25 °C. The growth rate of G′ in high temperature stage was lower than that in low temperature stage. Moreover, the structure formation in high temperature stage was chiefly dominated by hydrophobic interaction while that in low temperature stage was mainly governed by hydrogen bonding. The results presented herein were important to improve the quality of sugared foods by using high-methoxyl pectin as a texture modifier.