Water-Soluble Constituents of Fruit I. Some Observations on the Occurrence of Free Galacturonic Acid in Fruit

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Abstract
Glucuronic acid showed no tendency to convert the lactone when run on paper chromatograms in a variety of solvent mixtures. There were only slight differences between the RF values of glucuronic and galacturonic acids in all the solvents used, including two mixtures for which large differences in Rp had been recorded. By the use of paper chromatography, a free uronic acid was detected in several varieties of pears after ripening at 20[degree]C, but not in green or tree-ripened pears. Similar results were obtained with freestone peaches. No free uronic acid was detected in apricots whether ripened on the tree or at 20[degree]C. Chemical tests applied to the free uronic acid in pears, after elution from paper chromatograms, indicated that it was galacturonic acid. In the sample which gave the strongest uronic acid spot, the concentration of free galacturonic acid was 350ug/g fresh fruit.