are chemical and physical methods of detecting glucose which are entirely reliable, the utility of the composition of ash for this purpose is rather confirmatory than otherwise. Since the added sugar is the chief constituent of jams there is little difference in other respects in the composition of jams made from different fruits, as will be seen by the table of analysis given below:
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| Total | | Reducing | Cane | Total
Description. | Solids. | Acidity. | Sugar. | Sugar. | Sugar.
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Jams. | Percent. | Percent. | Percent. | Percent. | Percent.
Apple, | 63.22 | 0.282 | 25.52 | 29.11 | 54.63
Blackberry, | 55.42 | .851 | 18.77 | 29.00 | 47.77
Grape, | 56.64 | .744 | 33.44 | 11.33 | 44.77
Orange, | 80.52 | .433 | 13.61 | 54.23 | 67.84
Pear, | 61.52 | .163 | 13.20 | 33.74 | 46.94
Peach, | 65.65 | .500 | 36.48 | 23.16 | 59.64
Pineapple, | 73.92 | .314 | 14.05 | 46.40 | 60.45
Plum, | 50.43 | 1.012 | 28.29 | 9.70 | 37.99
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The characteristics of fruit which give the special flavors to the jams are imparted by constituents such as ethers, essential oils, and other aromatic substances, together with the free acids which are present in such quantities as not to be susceptible of easy quantitative determination by chemical means. The relation which exists between the cane sugar and the invert sugar is not a safe index of the method of preparation, but is rather an indication of the excess or deficiency of the acid in the fruit employed. The greater the quantity of active acids, other things being equal, the larger the quantity of inverted sugar and the smaller the quantity of cane sugar in the finished product.
In the following table is given the composition of a number of jams made in the laboratory of the Bureau of Chemistry. These analyses are selected from a great many which are available because the character and amount of sugar in the composition of the jam were carefully controlled, and thus the chemical data afford a base of direct composition.
Legend:
A: Total Solids.
B: Ash.
C: Total Acids Expressed as H_{2}SO_{4}.
D: Proteids (N × 6.25).
Sugars.
E: Reducing sugar.
F: Cane sugar added.
G: Cane sugar found.
H: Cane sugar inverted.
Polarizations.
I: Direct at 18° C.
J: Invert at 18° C.
K: Invert at 86° C.
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| | | | | | Sugars. | Polarizations.
Serial | Description of | | | | +-+-+-+-+-+-+-
Number. | Sample. | A. | B. | C. | D. | E. | F. | G. | H. | I. | J. | K.
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| | P. ct. | P. ct. | P. ct. | P. ct. | P. ct. | P. ct. | P. ct. | P. ct. | °V. | °V. | °V.
20446 | Apple (fall pippin) | 63.22 | 0.20 | 0.282 | 0.175 | 25.52 | 51.31 | 29.11 | 43.22 | +26.3 | -13.0 | +4.8
20414 | Blackberry | 55.42 | .48 | .851 | .737 | 18.77 | 43.99 | 29.00 | 34.08 | +24.6 | -14.6 | +1.6
20445 | Grape (fox) | 61.80 | .19 | .698 | .200 | 50.06 | 54.21 | 3.70 | 92.96 | -9.0 | -14.0 | +2.2
20416 | Grape (Ives seedling) | 56.64 | .48 | .744 | .525 | 33.44 | 42.45 | 11.33 | 73.38 | +3.5 | -11.8 | 0
20443 | Orange (Florida navel) | 80.52 | .44 | .433 | .944 | 13.61 | 69.13 | 54.23 | 21.55 | +55.9 | -17.5 | +2.0
20448 | Pear (Bartlett) | 61.52 | .28 | .163 | .312 | 13.20 | 46.52 | 33.74 | 18.87 | +32.3 | -13.2 | +1.0
20442 | Pineapple | 73.92 | .30 | .315 | .312 | 14.05 | 60.20 | 46.40 | 22.90 | +52.3 | -10.3 | +6.2
20421 | Plum (damson) | 50.43 | .54 | 1.102 | .525 | 28.29 | 37.75 | 9.70 | 74.42 | +3.1 | -10.0 | +1.2
20423 | Plum (wild fox) | 62.10 | .46 | 1.355 | .212 | 28.78 | 47.86 | 23.26 | 53.43 | +13.9 | -17.5 | 0
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