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United States Department of Agriculture

Agricultural Research Service

Title: A Comparison of Lime and Orange Pectin by Hpsgc with Molar Mass and Viscosity Detection

Authors
item Fishman, Marshall
item Chau, Hoa
item Coffin, David

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2003
Publication Date: April 1, 2003
Citation: Fishman, M.L., Chau, H.K., Coffin, D.R. A comparison of lime and orange pectin by hpsgc with molar mass and viscosity detection. Abstract. Villanova University, Villanova PA. April, 2003.

Technical Abstract: Pectin was acid extracted from lime albedo by microwave heating under pressure. Extraction times ranged from 1 to 10 minutes. Solubilized pectin was characterized for molar mass (M), rms radius of gyration (Rg) and intrinsic viscosity (IV) by HPSEC with online light scattering and viscosity detection. M, Rg and IV were relatively constant up to an extraction time of 3 minutes, but decreased rapidly thereafter. At heating times of 3.0 minutes or less, M, Rg and IV were significantly higher than a commercial citrus pectin. At a heating time of 2.5 minutes Mw was 335 x103, Rgz was 42 nm and IVw was 10.5 dL/g. These values were comparable to values for orange albedo pectin which were obtained previously by extraction with microwave heating under pressure (Fishman et al., Carbohydr. Res. 323, 126, 2000). Nevertheless, it was found that some lime pectin could be extracted more quickly and at lower temperature and pressure than orange albedo pectin. Chromatography revealed that solubilized lime and orange pectin gave distributions which were bimodal in nature. Mark-Houwink plots for pectin samples extracted at different times of heating revealed that lime and orange pectin became more asymmetric in shape when the molar mass decreased. These results indicated that at short extraction times, pectin was solubilized as compact aggregated networks or branched structures which were broken down to their more asymmetric components as heating time increased. Measurements made at the optimum pH revealed that the gel strength of lime pectin was highest, orange pectin was intermediate and commercial citrus pectin was the lowest of the pectins examined. The pH dependence of gel strength for each kind of pectin gave good fits when fitted to the equation which describes a Gaussian curve. The pH optimums were 3.53, 3.23 and 3.00 for lime, orange and commercial citrus pectin, respectively. This work demonstrates that it is now possible to utilize orange peel and pulp as a source of high value food grade pectin rather than low value animal feed.

Last Modified: 10/20/2014
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