Pectins gelation pectinic acid

Pectins are generally classed according to their ester content as high methoxyl pectins (>50% of the carboxyl groups esterified) or low methoxyl pectins (<50% of carboxyl groups esterified) (pectic acid, methyl ester [9049-34-1]). Low methoxyl pectins, like algins, require calcium for gelation. 

The gel/sol transitions cannot be distinguished for pectins extracted by after acid treatment and water-soluble pectins after extrusion. A minimal pectin concentration of 0.2% is required for gelation and no gels can be obtained below a sucrose concentration of 45 %. Commercial pectin (Hercules) with a dm 73 % has a lower phase transition line with a minimal pectin concentration of 0.1 % and sucrose concentration of 40 %. 

This capacity is applicable in various sectors of the food industry such as bioremediation, beverage processing, ascorbic acid determination, sugar-beet pectin gelation, and baking it also acts as a biosensor. 

Beet pectin and wheat-flour pentosans undergo an oxidative gelation (Neukom, 1976 Neukom and Markwalder, 1978) instigated by ferulic acid peroxidase through diferulic acid crosslinking. Crowe (1989) and Thibault et al. (1991) effected the same crosslinking with persulfate and chlorine, respectively. 

Owens, H.S., McReady, R.M. and Maclay, W.D. 1949. Gelation and characteristics of acid-precipitated pectinates, Food Technol., 3 77-82. 

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