title: Pectin as a rheology modifier: Origin, structure, commercial production and rheology.
abstract: Pectins are a diverse family of biopolymers with an anionic polysaccharide backbone of α-1,4-linked d-galacturonic acids in common. They have been widely used as emulsifiers, gelling agents, glazing agents, stabilizers, and/or thickeners in food, pharmaceutical, personal care and polymer products. Commercial pectin is classified as high methoxy pectin (HMP) with a degree of methylation (DM) >50% and low methoxy pectin (LMP) with a DM <50%. Amidated low methoxy pectins (ALMP) can be obtained through aminolysis of HMP. Gelation of HMP occurs by cross-linking through hydrogen bonds and hydrophobic forces between the methyl groups, assisted by a high co-solute concentration and low pH. In contrast, gelation of LMP occurs by the formation of ionic linkages via calcium bridges between two carboxyl groups from two different chains in close proximity, known as the 'egg-box' model. Pectin gels exhibit Newtonian behaviour at low shear rates and shear-thinning behaviour when the shear rate is increased. An overview of pectin from its origin to its physicochemical properties is presented in this review.
authors.affiliation: School of Science, Monash University Malaysia, 47500 Bandar Sunway, Selangor Darul Ehsan, Malaysia; Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, #08-03, Singapore 138634, Singapore.
authors.forename: Siew Yin
authors.initials: SY
authors.lastname: Chan
authors.affiliation: School of Science, Monash University Malaysia, 47500 Bandar Sunway, Selangor Darul Ehsan, Malaysia. Electronic address: choo.wee.sim@monash.edu.
authors.forename: Wee Sim
authors.initials: WS
authors.lastname: Choo
authors.affiliation: School of Science, Monash University Malaysia, 47500 Bandar Sunway, Selangor Darul Ehsan, Malaysia; Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, #08-03, Singapore 138634, Singapore; Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore DC, Queensland 4558, Australia. Electronic address: dyoung1@usc.edu.au.
authors.forename: David James
authors.initials: DJ
authors.lastname: Young
authors.affiliation: Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, #08-03, Singapore 138634, Singapore; Department of Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore; Singapore Eye Research Institute (SERI), 11 Third Hospital Avenue, Singapore 168751, Singapore. Electronic address: lohxj@imre.a-star.edu.sg.
authors.forename: Xian Jun
authors.initials: XJ
authors.lastname: Loh
mesh_terms: D005782:Gels / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D010368:Pectins / Q000138:chemical synthesis / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D012212:Rheology; D012996:Solutions
chemical_list: D005782:Gels; D011108:Polymers; D012996:Solutions; D010368:Pectins
keywords: Extraction; Gelling mechanisms; Hydrogels; Hydrogen bonding; Hydrophobic interactions; Ionic interactions; Pectin; Polysaccharide; Rheology; Rheology modifier