THE CURING OF TOBACCO LEAF
OBJECTS OF CURING. METHODS.
THE CURING OF TOBACCO LEAF
The "curing" of tobacco leaf is the process of drying out which has for
its object the following specific actions:
(1) The expelling of the sap and superfluous moisture.
(2) The completion of the "yellowing" process and the fixing of the
desired color.
(3) The preservation of the juices, etc., which give the
characteristic flavor and aroma.
(4) To give the necessary toughness and suppleness to the leaf.
The first part of the curing is done by the grower in curing sheds on the
farm immediately after the cutting of the crop; the final part, or the
fermentation part is usually done by the leaf dealer or manufacturer in
special buildings called leaf-houses.
There are three methods of curing in use by the growers, i. e., sun
curing, air curing, and artificial heat curing. In the case of the tobacco
known as _Perique_ the curing process is more or less peculiar to itself.
"Sun" and "air" curing are much slower processes than the curing by
artificial heat.
All cigar leaf tobacco is sun-cured, and as a general rule pipe smoking
and chewing tobacco are cured by artificial heat.
For the purpose of drying and curing by artificial heat, the leaf is hung
up in specially constructed curing houses or sheds. It is found that after
the exposure to the sun for the first process of "yellowing" tobacco leaf
still contains 1 lb. of water approximately in each plant. The first part
of the process of curing consists in drawing off this superfluous
moisture. Dry heat is applied at a temperature of 90 deg. F. to 120 deg. F. for
about 16 to 30 hours to effect this. A further exposure of about 48 hours
at a temperature of 125 deg. or so is necessary to complete the curing, and
fix the color.
The stems and stalks being thicker take a longer time and generally
require 9 to 10 hours further exposure and a temperature which may range
as high as 175 deg. F. before they are fully cured, the temperature being
graded hourly until the maximum necessary is reached.
The process of curing varies considerably in different states. Some
growers prefer to put the tobacco into the sheds immediately after
cutting, and allow very little exposure in the fields. The temperature is
usually kept steady at about 90 deg. F. Again the process is different
according to the quality of tobacco required. For the heavy type of leaf
which is intended for the export trade, the curing in the sheds is done by
an _open_ fire, the fuel being usually hardwood logs. The smoky, creosotic
flavor is absorbed by the leaf, and, although this flavor is not relished
by the smokers of the U. S., it is much liked in Europe. The curing in
such cases may last for 4 or even 5 days. The tobacco is suspended on
poles by the stalks and the fires are built on the floor immediately under
them so that the carbonaceous products are easily absorbed by the open
pores of the leaf.
The chewing and pipe smoking tobacco, as well as cigarette tobaccos
including all the bright yellow tobaccos used in the U. S. are usually
cured by _Flue_ curing. In this case the heat comes from pipes which run
around the curing houses and are fed from a furnace in an adjoining
chamber or in a cellar. The temperature can be easily regulated. "Flue"
curing is generally completed in about 4 days. "Flue" curing does not clog
up the pores of the leaf which therefore remain more absorbent than in the
open fire cured tobacco. This is an important matter for the manufacturers
because the flue cured leaf will absorb twice as much of the flavoring
sauces (which are added to certain kinds of tobacco) than tobacco leaf
cured by open fires.
Air exposure of 6 to 8 weeks (sometimes extended to 3 or 4 months) is
necessary when tobacco is cured by exposure to the sun and air. It is
claimed, however, that this method of curing preserves far better the
natural flavor of the leaf; and, where flavor and aroma are highly
important, this method is always preferred. Hence all cigar leaf tobaccos
are cured by exposure to natural sunlight and not by artificial heat.
"Air" curing as distinct from sun curing is generally done in open sheds
which are thoroughly ventilated and kept as far as possible at a
temperature of about 75 deg. F. The leaf is usually allowed to cure while
attached to the stalk, but Florida curers generally prefer to strip the
leaf and treat it separately. The finer classes of pipe smoking tobaccos
are air cured.
After the curing is completed the color of the leaf is usually fixed.
Generally speaking, the riper the leaf the lighter will be its color when
cured. Thus the bottom leaves of the plant will be lighter in color than
the upper leaves because they are more mature.
(_For references see end of Chapter VIII_)