Moderate amount of lecithin improving rheological properties of low-methoxyl apple pectin gel

Pectins were traditionally applied in food industry as well as other industries such as pharmaceutical industry as typical gelling, emulsifying, thickening and stabilizing agents. Lecithin, a highly compatible lipid and an important constituent of biological membranes, is applied to the pectin gel as a colon-specific carrier in recent years. In order to investigate the gel properties of pectin, the effects of soybean lecithin on the rheological properties of low-methoxyl apple pectin gels were studied in this paper. The weight average molecular weight of pectin obtained by the size exclusion chromatograph method was 1.27×105, the number average molecular weight was 3.77×104, and thus the molecular weight distribution index was 3.36. In the presence of calcium ion, adding different proportions of lecithin to low-methoxyl apple pectin, the storage modulus (G') and loss modulus (G) were recorded through the observation during the gelation process of the pectin, when the plate was cooled from 80 to 26℃ at a certain rate with the rheological technology. Then the structure development rate (SDR) analysis method was adopted to explore the effects that the presence of lecithin brought to the gelation system in the gelation process of pectin. The results showed that the addition of lecithin had significant effects on SDR and G'. With a low amount of lecithin (0.4%), SDR and G' tended to decrease. The average structure developing rate and the end storage modulus showed the same tendency as above; when adding 0.4% lecithin, the average structure developing rate increased to 4.2 Pa/s and the end storage modulus increased to 2950 Pa; both of them were significantly higher than the sample without lecithin (P ©, 2015, Chinese Society of Agricultural Engineering. All right reserved.