less desirable and suitable for consumption. For this reason, among others, the precaution above mentioned, namely, that the fruit should not be overripe, should be observed. It has been seen that overripe fruit diminishes in acidity, and hence it is less suitable for converting the cane sugar than fruit just short of complete maturity. For this reason, too, the more strongly acid fruits are better suited for making these sweetened products than those in which the acidity is less strongly developed.
Jams.—As has already been said, jams differ from jellies in that they contain not only the juice of the fruit but the whole pulp of the fruit or the whole fruit. The methods of preparation in effect produce the same changes upon the sugars that are produced by the fruit juice. The fruit after proper comminution is boiled with large quantities of sugar a sufficient length of time to reduce the fruit flesh to a pulp and to invert more or less of the sugar which is used. The insoluble matter which jam contains consists chiefly of the cellulose and pectose matter in the fruit, together with the seeds of the small fruit. The various solids are made up of the solid bodies in the fruits, including the sugars which are added. The character of the ash of the jams is a good indication whether or not they are pure, that is, made out of sugar and fruit only. While it is true that the ash of fruit varies, it is also true that the real ash of fruit has certain characteristics in regard to alkalinity which are not possessed by the ash of adulterated fruit products. For the sake of convenience and reference it is seen advisable to append a table showing the composition of the ash of some of the fresh fruits (Bulletin 66, Bureau of Chemistry).
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| | K_{2}O. | Na_{2}O. | CaO. | P_{2}O_{5}. | SO_{3}. | Cl.
Fruit. | Pure Ash | Potash. | Soda. | Lime. | Phosphoric | Sulfuric | Chlorin.
| | | | | Acid. | Acid. |
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| Percent. | Percent. | Percent. | Percent. | Percent. | Percent. | Percent.
| | | | | | |
Apple, | 0.264 | 55.21 | 11.69 | 4.79 | 12.83 | 4.62 | 0.83
Apricots, | .508 | 59.36 | 10.26 | 3.17 | 13.09 | 2.63 | .45
Banana, | 1.078 | 63.06 | 2.34 | .86 | 1.62 | 2.32 | 26.93
Cherries, | 0.440 | 57.67 | 6.80 | 4.20 | 15.11 | 5.83 | 1.83
Figs, | .682 | 57.16 | 2.38 | 10.90 | 12.76 | 3.90 | 2.05
Grapes, | .500 | 50.95 | 6.32 | 4.96 | 21.27 | 4.28 | 1.54
Lemons, | .526 | 48.26 | 1.76 | 24.87 | 11.09 | 2.84 | .39
Oranges, | .432 | 48.94 | 2.50 | 22.71 | 12.37 | 5.25 | .92
Prunes, | .486 | 63.83 | 2.65 | 4.66 | 14.08 | 2.68 | .34
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From the above table it is seen that there is not a very large percentage of sulfuric acid in the natural ash in fruits, and very little chlorin, with the exception of the banana, in which the ash is principally potassium chlorid. Since the ash of glucose, as it is made at the present time, consists almost entirely of sulfates and chlorids, any considerable increase of these ingredients of an ash over the normal may be regarded as an indication that the fruit product from which the ash is obtained contains added glucose. Inasmuch as there
