d essential oils.
During storage some apples appear to undergo further ripening, resulting
in partial inversion of the sucrose, and there is a slight loss of
weight, due to the formation of carbon dioxide. The apple is an
important and valuable adjunct to the dietary.[22]

[Illustration: FIG. 12.--GRAPHIC COMPOSITION OF APPLE.]

[Illustration: FIG. 13.--GRAPHIC COMPOSITION OF ORANGE.]

60. Oranges contain nearly the same proportion of dry matter as
apples, the larger part of which is sugar. Citric acid predominates and
ranges in different varieties from 1 to 2.5 per cent. The amounts of
protein, fat, and cellulose are small. In some varieties of oranges
there is more iron and sulphur than is usually found in fruits. All
fruits, however, contain small amounts, but not as much as is found in
green vegetables. The average composition of oranges is as follows:

===========================================================
PHYSICAL COMPOSITION|CHEMICAL COMPOSITION OF EDIBLE PORTION
-----------------------------------------------------------
Per Cent| Per Cent
Rind 20 to 30| Solids 10 to 16
Pulp 25 to 35| Sugars 8 to 12
Juice 35 to 50| Citric acid 1 to 2.5
| Ash 0.5
===========================================================

61. Lemons differ from oranges in containing more citric acid and less
sucrose, levulose, and dextrose. The ash of the lemon is somewhat
similar in general composition to the ash of the orange, but is larger
in amount. The average composition of the lemon is as follows:

===========================================================
PHYSICAL COMPOSITION|CHEMICAL COMPOSITION OF EDIBLE PORTION
-----------------------------------------------------------
Per Cent| Per Cent
Rind 25 to 35| Solids 10 to 12
Pulp 25 to 35| Sugar 2 to 4
Juice 40 to 55| Citric acid 6 to 9
===========================================================

62. Grape Fruit.--The rind and seed of this fruit make up about 25 per
cent, leaving 75 per cent as edible portion. The juice contains 14 per
cent solids, of which nearly 10 per cent is sugar and 2.5 per cent is
citric acid. There is more acid in grape fruit than in oranges and
appreciably less than in lemons. The characteristic flavor is due to a
glucoside-li