f their stock. But were it feasible to treat and hold
coffees long enough to develop their attributes to a maximum, still the
exact conditions which would favor such development are not definitely
known. What are the optimum temperature and the correct humidity to
maintain, and should the green coffee be well ventilated or not while in
storage? How long should coffee be stored under the most favorable
conditions best to develop it? Aging for too long a period will develop
flavor at the expense of body; and the general cup efficiency of some
coffees will suffer if they be kept too long.

[Illustration: PORTION OF THE INVESTING MEMBRANE, SHOWING ITS STRUCTURE

Drawn with the camera lucida, and magnified 140 diameters]

The exact reason for improvement upon aging is in no wise certain, but
it is highly probable that the changes ensuing are somewhat analogous to
those occurring in the aging of grain. Primarily an undefined enzymatic
and mold action most likely occurs, the nature of the enzymes and molds
being largely dependent upon the previous treatment of the coffee. Along
with this are a loss of moisture and an oxidation, all three actions
having more evident effects with the passage of time.

_Artificial Aging_

In consideration of the higher prices which aged products demand,
attempts have naturally been made to shorten by artificial means the
time necessary for their natural production. Some of these methods
depend upon obtaining the most favorable conditions for acceleration of
the enzyme action; others, upon the effects of micro-organisms; and
still others, upon direct chemical reaction or physical alteration of
the green bean.

One of the first efforts toward artificial maturing was that of
Ashcroft[109], who argued from the improved nature of coffee which had
experienced a delayed voyage. His method consisted of inclosing the
coffee in sweat-boxes having perforated bottoms and subjecting it to the
sweating action of steam, the boxes being enclosed in an oven or room
maintained at the temperature of steam.

[Illustration: STRUCTURE OF THE GREEN BEAN

Showing thick-walled cells enclosing drops of oil]

Timby[110] claimed to remove dusts, foreign odors, and impurities, while
attaining in a few hours or days a ripening effect normally secured only
in several seasons. In this process, the bagged coffee is placed in
autoclaves and subjected to the action of air at a pressure of 2 to 3
atmospheres and a tempe