se it has been melted from the bean by the hot
water and carried along with the solution.

The caffein furnishes the stimulation for which coffee is generally
consumed. It has only a slightly bitter taste, and because of the
relatively small percentage in which it is present in a cup of
coffee, does not contribute to the cup value. The mineral matter,
together with certain decomposition and hydrolysis products of
crude fiber and chlorogenic acid, contribute toward the astringency
or bitterness of the cup. The proteins are present in such small
quantity that their only role is to raise somewhat the almost
negligible food value of a coffee infusion. The body, or what might
be called the licorice-like character of coffee, is due to the
presence of bodies of a glucosidic nature and to caramel.

As has been previously pointed out[382], the term "caffetannic
acid" is a misnomer; for the substances which are called by this
name are in all probability mainly coffalic and chlorogenic acids.
Neither is a true tannin, and they evince but few of the
characteristic reactions of tannic acid. Some neutral coffees will
show as high a "caffetannic acid" content as other acid-charactered
ones. Careful work by Warnier[383] showed the actual acidities of
some East Indian coffees to vary from 0.013 to 0.033 percent. These
figures may be taken as reliable examples of the true acid content
of coffee, and though they seem very low, it is not at all
incomprehensible that the acids which they indicate produce the
acidity in a cup of coffee. They probably are mainly volatile
organic acids together with other acidic-natured products of
roasting.

[Illustration: SECTION OF ROASTED BEAN MAGNIFIED 1,000 TIMES]

We know that very small quantities of acid are readily detected in
fruit juices and beer, and that variation in their percentages is
quickly noticed, while the neutralization of this small amount of
acidity leaves an insipid drink. Hence it seems quite likely that
this small acid content gives to the coffee brew its essential
acidity. A few minor experiments on neutralization have proven the
production of a very insipid beverage by thus treating a coffee
infusion. So that the acidity of certain coffees most apparently
should be attributed to such compounds, rather