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Quantitative Distribution of Phosphorus and Calcium in Certain Fruits and Vegetables

Department of Chemistry, Columbia University, New York

Quantitative studies have been made of the relative amounts of phosphorus in the flesh and seeds of seven species of fruits; in the pods and ovules of four varieties of beans; in the leaves, the edible stems, and the flowerbuds of broccoli; and of calcium in the same parts of broccoli, and in the flesh (juice and pulp) and septa of oranges.

In the course of this work, either phosphorus or calcium was determined in from four to ten entirely separate specimens each, obtained through ordinary marketing channels in a city supplied from widely varied sources, of twelve foods representing edible stems, leaves, flowerbuds, fruits, and edible seeds. In only one-sixth of these foods was the average deviation in phosphorus or calcium content as much as one-tenth of the mean.

Allowing for the extent of the variations encountered in fruits and vegetables as actually produced and marketed, the following findings may be regarded as sufficiently established:

In such "small fruits" as blackberries, currants, and raspberries, the phosphorus content is significantly different when the "edible portion" of the fruit is analyzed with and without the seeds.

In the grapes here studied, the seeds show three times as high a percentage of phosphorus as the flesh, but constitute so small a proportion of the whole fruit as scarcely to influence its average composition.

In tomatoes, okra, and squash (fruits commercially classified as vegetables) the phosphorus content of the edible portion was measurably influenced by the inclusion or exclusion of the seeds. To what extent human beings can assimilate the phosphorus of these seeds remains to be studied.

The quantitative aspect of the transfer of phosphorus from pods to ovules in maturing beans is found to be striking.

Also well marked is the concentration of calcium in the septa of oranges as compared with the juice. The latter, even when carrying the softer portions of the pulp, was found to contain only 27% of the calcium of the edible portion.

The data here reported will also add to the material available to investigators of the natural variability of foods.