Sugar and Acid in Fruit.

The palatable quality of fruit depends largely upon the aromatic substances which they contain in the form of essential oils, esters, and ethers, and especially upon their sugar and acid content. The sweet taste of sugar in fruits and also often in nuts is modified and relieved by the acid or astringent materials, chiefly tannin, with which it is associated. In the analyses indicating the composition of fruits and of nuts and also of vegetables the sugar has not always been given separately, but as one member of a group consisting of sugar, starch, and cellulose materials soluble in weak acid and alkalies, and for this reason deemed to be digestible. It seems advisable to supplement this information with a special table giving the average quantity of sugar and acid found in some of the principal fruits. It must not be forgotten that in individual cases the quantity of sugar and acid may vary largely from the average, but the following data may be regarded as expressing very accurately the average content of sugar and acid in the common fruits.

	Sugar. Percent.		Acid. Percent.
Apples, Rhode Island Greening,	10.95		.70	as	malic
Apples, Winesap,	11.95		.50	„	„
Apples, Northern Spy,	11.80		.70	„	„
Apricots, fresh,	11.01		1.15	„	„
Apricots, dried,	29.59		2.52	„	„
Bananas,	20.28		.30	„	sulfuric
Blackberries,	5.78		.77	„	malic
Cranberries,	1.52		2.34	„	„
Currants,	6.70		2.24	„	„
Grapes,	7.90	-26.40	.59	„	tartaric
Lemons,	.37		5.39	„	citric
Oranges,	5.65		1.35	„	„
Peaches,	7.88		.56	„	sulfuric
Pears,	9.11		.19	„	malic
Pineapples,	11.50		.60	„	sulfuric
Plums,	14.71		.77	„	malic
Prunes,	16.11		.32	„	„
Raspberries,	5.33		1.48	„	„
Strawberries,	6.24		1.10	„	„

In the above data the acidity is determined as malic acid in apples, blackberries, and strawberries, in which the predominant acid is malic. In cranberries one of the acids is benzoic, amounting sometimes to as much as 0.05 percent, in grapes tartaric, in lemons and oranges citric. In the other fruits where the character of the organic acid is not distinctly of one kind, the total organic acid is estimated as sulfuric acid (SO₃), not meaning by that, however, that the acids are present in the form of sulfuric acid but merely that their quantity was measured in terms of sulfuric acid.