NFS386H1 Study Guide - Midterm Guide: Gel Permeation Chromatography, Thickening Agent, Limonene
5 Jan 2019
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Document Summary
Pectin is a heteropolysaccharide with a chain structure of a-d-galacturonic acid units interrupted by the insertion of l-rhamnopyranosyl residues. Pectin contains side chains of neutral sugars attached are randomly (i. e. not evenly distributed) on either the galacturonic or rhamnopyranosyl. Pectin traditionally used as a gelling agent for jam or jam-like foods. Mostly citrus peels but also sometimes apple pomace. Two different mechanisms as to how it works as a gelling agent: the alignment of molecular helices that are held together by hydrogen bonding and hydrophobic interactions. High-ester pectin forms gels at low ph (< 3. 5) and in the presence of high solid contents, typically sucrose (>= 55% []). At high ph, the carboxylic groups on the pectin are dissociated and this leads to electrostatic repulsion between the chains. The cosolute creates low water activity conditions that promote pectin chain-chain interactions. Low-ester pectins instead requires the presence of divalent cations (ex.
