Cinnamon Apple Pectins: Structural and Rheological Properties

Abstract

The structural and viscoelastic characteristics of pectins (CAP) extracted from cinnamon apple pomace, under different acid conditions, were investigated. The yield of pectins ranged from 2.8 to 10.9% and was significantly ( P <0.05) affected by the solvent strength. The optimum yield (11.0%) was recorded at pH 1.2 as the other extraction parameters, viz. temperature, time, and solid to liquid ratio were kept constant to 75 °C, 90 min, and 1:25 (w/v), respectively. The main monosaccharide constituents of CAP were galacturonic acid, arabinose, galactose, and rhamnose; thus suggesting that the pectic polymers were built of linear homogalacturonan and non-linear rhamnogalacturonan block copolymers branched with arabinose- and/or galactose-containing side chains. Enzymatic degradation of CAP indicated that the neutral sugar side chains were mainly galactoarabinans with some arabinogalactans. However, the b-Galactosyl Yariv assay, specific to 1,3-b-galactan, was found to be negative, indicating that detected arabinogalactans might “exclusively” be of type I. The degree of methylesterification was in the range of 43-68%, showing extraction of both low (HMP) and high methoxy (LMP) pectins. The trends of sugar-acid-mediated gelation of the purified CAP were significantly different from one another ( P <0.05), as judged by the conventional SAG method (gel strength) and by small amplitude oscillatory shear tests (viscoelastic properties). Depending on the extraction conditions, potentially good LMP and HMP can be produced from cinnamon apple pomace.