Ciencia De La Comida

Innovative Food Science and Emerging Technologies 11 (2010) 401–409

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Innovative Food Science and Emerging Technologies
j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / i f s e t

Influence of pectin structure on texture of pectin–calcium gels
Ilse Fraeye a, Ines Colle a, Evelien Vandevenne a, Thomas Duvetter a, SandyVan Buggenhout a, Paula Moldenaers b, Ann Van Loey a,⁎, Marc Hendrickx a
a

Laboratory of Food Technology, Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (M2S), Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, Box 2457, B-3001 Leuven, Belgium b Applied Rheology and Polymer Processing Section, Department of Chemical Engineering,Katholieke Universiteit Leuven, Willem de Croylaan 46, B-3001 Leuven, Belgium

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A library of pectins with varying degree and pattern of methoxylation was produced by demethoxylating a parent pectin by use of NaOH or pectinmethylesterase from plant or fungal origin. Additionally, pectin was chemically depolymerised by a heat treatment. The resultingpectins were characterised in terms of degree and pattern of methoxylation (“(absolute) degree of blockiness”) and the extent of depolymerisation. Pectin–calcium gels were prepared and their texture was studied by performing compression tests. From the resulting force vs. distance curves, the modulus of elasticity under low strain and the fracture stress and strain were determined. The modulus ofelasticity under low strain increased with decreasing degree of methoxylation. At very low degree of methoxylation, gels were brittle, resulting in low fracture stress. Both modulus of elasticity and fracture stress correlated more with degree of blockiness and absolute degree of blockiness as compared to degree of methoxylation. Gel strength increased with increasing Ca2+ or pectin concentration.Depolymerisation of pectin resulted in formation of brittle gels. Industrial relevance: Pectin with low degree of methoxylation can form a gel in presence of calcium. Therefore, it is widely used in the food industry. In addition, pectin-calcium interactions are of importance for the texture of fruits and vegetables, since crosslinked pectin in the cell wall provides cell-cell adhesion and mechanicalstrength of tissues. This research is focused on textural characteristics of pectin-calcium gels. It is shown that pectin structural properties influence texture of gels. As a result, control of pectin structure allows fine-tuning of functional properties. © 2009 Elsevier Ltd. All rights reserved.

Article history: Received 19 May 2009 Accepted 23 August 2009 Editor Proof Receive Date 9 September2009 Keywords: Pectin Gelation Texture Degree of blockiness

1. Introduction Pectin is a cell wall polysaccharide with complex chemical and macromolecular organisation, the exact architecture is still being explored (Vincken et al., 2003; Coenen, Bakx, Verhoef, Schols, & Voragen, 2007). One of the main domains in pectin is homogalacturonan, a linear chain consisting of α-(1,4)-linkedgalacturonic acid (GalA) residues, part of which can be esterified with methanol. The percentage of GalA that is methoxylated is defined as the degree of methoxylation (DM). The DM of pectin is generally considered to be one of the main parameters determining its functionality (Thibault & Ralet, 2003). In the presence of sugars, pectin with high DM can form a gel in acidic media. On the other hand, pectin withlow DM contains a higher amount of free carboxylic acid groups, which can interact with divalent ions such

Abbreviations: DB, degree of blockiness; DBabs, absolute degree of blockiness; DM, degree of methoxylation; DP, degree of polymerisation; GalA, galacturonic acid; HPAECPAD, high performance anion exchange chromatography pulsed amperometric detection; HPSEC, high performance size...