the principal coloring matters in coffee infusion. That portion
of the carbohydrates known as pentosans gives rise to furfuraldehyde,
one of the important components of caffeol.

The effect of roasting upon the fat content of the beans is to reduce
its actual weight, but not to change appreciably the percentage
present, since the decrease in quantity keeps pace fairly well with the
shrinkage. Some of the more volatile fatty acids are driven off, and the
fats break down to give a larger percentage of free fatty acids, some
light esters, acrolein, and formic acid. If the roast be a very heavy
one, or is brought up too rapidly, the fat will come to the surface,
through breaking of the fat cells, with a decided alteration in the
chemical nature of the fat and with pronounced expansion and cracking.

Decomposition of the caffein acid-salt and considerable sublimation of
the caffein also occur. The majority of the caffein undergoes this
volatilization unchanged, but a portion of it is probably oxidized with
the formation of ammonia, methylamin, di-methylparabanic acid, and
carbon dioxid. This reaction partly explains why the amount of caffein
recovered from the roaster flues is not commensurate with the amount
lost from the roasting coffee; although incomplete condensation is also
an important factor. Microscopic examination of the roasted beans will
show occasional small crystals of caffein in the indentations on the
surface, where they have been deposited during the cooling process.

The compound, or compounds, known as "caffetannic acid" are probably the
source of catechol, as the proteins are of ammonia, amins, and pyrrols.
The crude fiber and other unnamed constituents of the raw beans react
analogously to similar compounds in the destructive distillation of
wood, giving rise to acetone, various fatty acids, carbon dioxid and
other uncondensable gases, and many compounds of unknown identity.

During the course of roasting and subsequent cooling these decomposition
products probably interact and polymerize to form aromatic tar-like
materials and other complexes which play an important role among the
delicate flavors of coffee. In fact, it is not unlikely that these
reactions continue throughout the storage time after roasting, and that
upon them the deterioration of roasted coffee is largely dependent.
Speculation upon what complex compounds are thus formed offers much
attraction. A notable one by Sayre[162] postulates