Stiffness of Ca(2+)-pectin gels: combined effects of degree and pattern of methylesterification for various Ca(2+) concentrations.
The influence of the degree and pattern of methylesterification (DM and PM, respectively) on the stiffness of Ca(2+)-pectin gels is extensively examined, at various Ca(2+) concentrations. Accordingly, a highly methyl-esterified pectin was selectively de-esterified using NaOH, plant or fungal pectin methylesterase in order to produce series of pectins with varied pattern and broad ranges of methylesterification. The PM was quantified as absolute degree of blockiness (DB(abs)). Ca(2+)-pectin gels were prepared at various Ca(2+) concentrations. Gel stiffness (G' at 1rad/s) was determined and mapped out as a function of DM, DB(abs) and Ca(2+) concentration. At low Ca(2+) concentrations, G' depends on polymer's DM and DB(abs). At high Ca(2+) concentrations, a master curve is obtained over a wide range of DM, irrespective of DB(abs). Depending on methylesterification pattern, increase of G' is related not only to an increase in the number of junction zones per pectin chain, but also to an increase in the size of junction zones and the number of dimerised chains occurring in the gels. These results provide a detailed insight into the occurrence of junction zones in Ca(2+)-pectin gels.
Laboratory of Food Technology, Leuven Food Science and Nutrition Research Centre, Department of Microbial and Molecular Systems (M(2)S), Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, PO Box 2457, BE-3001 Leuven, Belgium.
Doungla E
DE
Ngouémazong
Ruben P
RP
Jolie
Ruth
R
Cardinaels
Ilse
I
Fraeye
Ann
A
Van Loey
Paula
P
Moldenaers
Marc
M
Hendrickx
D002118:Calcium / Q000737:chemistry*; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry; D004952:Esters / Q000737:chemistry; D005782:Gels; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D008738:Methyl Ethers / Q000737:chemistry; D008958:Models, Molecular; D010368:Pectins / Q000737:chemistry*; D012212:Rheology; D012972:Sodium Hydroxide / Q000737:chemistry
D004952:Esters; D005782:Gels; D008738:Methyl Ethers; D012972:Sodium Hydroxide; D010368:Pectins; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase; D002118:Calcium