Study on the relationship between primary structure/ spatial conformation and gel properties of pectins from different varieties

The structural characteristics of pectin vary considerably among varieties, which causes differences in gel properties. In this study, the relationships among the primary structure, spatial conformation, and gel properties of pectins extracted from grapefruit, apple, bigarade, mango, watermelon, and sugar beet were investigated. The six pectins were all high methoxyl pectins, each having a different degree of methyl esterification (DE). The sugar beet pectin with the lowest DE (54.7%) and loosest conformation (maximum Dmax, 63 nm) exhibited poor gelation properties. Apple pectin, which had a higher molecular weight (314 kDa), the highest DE (77.8%), and a compact conformation (Dmax, 40 nm) showed superior gelation. The compact conformation of pectins contributed to the formation of hydrophobic forces and hydrogen bonds within close proximity of molecules, resulting in a stable three-dimensional network. These results demonstrate that the primary structure and spatial conformation together affect the gelation properties of pectins, and provide new insight into the relationship between the chemical structure and gelation properties of pectins from different varieties.