, C_8_H_8_O_4, which he named caffeic acid.

The starch content of coffee is very low. Cereals may readily be
detected and identified in coffee mixtures by the presence and
characteristics of their starch, in view of the fact that coffee
(chicory, too) is practically free from starch. On this score it is
inadvisable for diabetics to use any of the many cereal substitutes for
coffee. It is pertinent to note in this connection that persons
suffering from diabetes may sweeten their coffee with saccharin (1/2 to
1 grain per cup) or glycerol, thus obtaining perfect satisfaction
without endangering their health.

The cellulose in coffee is of a very hard and horny character in the
green bean, but it is made softer and more brittle during the process of
roasting. It is rather difficult to define under the microscope,
particularly after roasting, even though the chief characteristics of
the cellular tissue are more or less retained. Coffee cellulose gives a
blue color with sulphuric acid and iodin, and is dissolved by an
ammoniacal solution of copper oxid. Even after roasting, remnants of the
silver skin are always present, the structure of which, a thin membrane
with adherent, thick-walled, spindle-shaped, hollow cells, is peculiar
to coffee.

_The Chemistry of Roasting_

The effect of the heat in the roasting of coffee is largely evidenced as
a destructive distillation and also as a partial dehydration. At the
same time, oxidizing and reducing reactions probably occur within the
bean, as well as some polymerization and inter-reactions.

A loss of water is to be expected as the natural outcome of the
application of heat; and analyses show that the moisture content of raw
coffee varies from 8 to 14 percent, while after roasting it rarely
exceeds 3 percent, and frequently falls as low as 0.5 percent. The loss
of the original water content of the green bean is not the only moisture
loss; for many of the constituents of coffee, notably the carbohydrates,
are decomposed upon heating to give off water, so that analysis before
and after roasting is no direct indication of the exact amount of water
driven off in the process. If it be desired to ascertain this quantity
accurately, catching of the products which are driven off and
determination of their water content becomes necessary.

The carbohydrates both dehydrate and decompose. The result of the
dehydration is the formation of caramel and related products, which
comprise