A biochemical study of the insoluble pectic substances in vegetables
American Journal of Botany 13(9): 531-547
The Carre method for the quantitative determination of proto-pectin in fruits, with slight modifications of heating, temp., and acidity, can be used on vegetable tissues, providing pectic acid or pectates are absent. When the latter are present, it is necessary to use a combined method of hydrolysis and extraction wherein the proto-pectin is hydrolyzed with N/30 HC1 and the pectic acid or its salts dissolved in 0.5% ammonium citrate solution. The resulting pectin and pectic acid may be quantitatively separated and determined. In vegetable and fruit tissues, pectic acid and its salts are probably of rare occurrence but pectic acid is rapidly formed in a number of them from protopectin during the usual methods of drying.