Boiling is a much more common operation than any of those we have
considered, with the exception perhaps of roasting. It consists, as
every body knows, in subjecting the materials of food to the influence
of heat, through the medium of boiling water, or of steam.
The water employed for boiling meat or pulse should be soft, and the
joint should be put on the fire immersed in cold water, in order that
the heat may gradually cause the whole mass to become boiled equally.
If the piece of meat is of an unequal thickness, the thinner parts will
be over-done before the more massy portion is sufficiently acted on by
the boiling water.
Salted meat requires to be very slowly boiled, or simmered only, for a
quick and rapid ebullition renders salted provisions extremely hard.
Frozen substances should be thoroughly thawed, and this is best effected
by immersing them in cold water.
Count Rumford has taken much pains to impress on the minds of those who
exercise the culinary art, the following simple but pratical, important
fact, namely, that when water begins only to be agitated by the heat of
the fire, it is incapable of being made hotter, and that the violent
ebullition is nothing more than an unprofitable dissipation of the
water, in the form of steam, and a considerable waste of fuel.
From the beginning of the process to the end of it the boiling should be
as gentle as possible. Causing any thing to boil violently in any
culinary process, is very ill-judged; for it not only does not
expedite, in the smallest degree, the process of cooking, but it
occasions a most enormous waste of fuel, and by driving away with the
steam many of the more volatile and more savoury particles of the
ingredients, renders the victuals less good and less palatable: it is
not by the bubbling up, or _violent boiling_, as it is called, of the
water that culinary operations are expedited.
One of the most essential conditions to be attended to in the boiling of
meat is, to skim the pot well, and keep it really boiling, the slower
the better. If the skimming be neglected, the coagulated albuminous
matter will attach itself to the meat, and spoil the good appearance of
it.
It is not necessary to wrap meat or poultry in a cloth, if the pot be
carefully skimmed. The general rule of the best cooks is to allow from
20 to 30 minutes slow simmering to a pound of meat, reckoning from the
time the pot begins to boil.
The cover of the boiling pot should fit close, to prevent the
unnecessary evaporation of the water, and the smoke insinuating itself
under the edge of the cover, and communicating to the boiled substance a
smoky taste.
Cooks often put a trevet, or plate, on the bottom of the boiling pot, to
prevent the boiled substance sticking to the pot.
_Rationale._--When flesh or fish is boiled in an open vessel, or one not
closely covered, the fibrous texture is rendered more tender: at the
same time its nutritive quality is not much diminished. For the
temperature of the water or steam, never exceeding 212°, is insufficient
to produce the partial charring, which roasting and broiling effect.
But, as in stewing, the gelatine, albumen, osmazome, and fat, are
developed and disengaged, and becoming united with the liquid in the
vessel, form a soup, or broth. The paler colour of boiled meat is owing
to the blood being separated and diffused in the water. In frying, the
boiling fat or oil enters into the interstices of the fibres, which the
disengaged animal juices have left empty. In boiling, in a similar way,
the hot water takes the place of the blood, gelatine, fat, and albumen,
which have been dissolved and separated from the fibres. The fibres are
in this manner soaked and washed, first by the boiling water, and
afterwards by the soup or broth which is formed, till the whole texture
assume a softened consistence, and pale appearance. It is this, rather
than any softening of the fibres themselves, which seems to be the real
effect produced, unless, with some, we consider the fibres as nothing
more than minute and close-set bundles of blood vessels. This doctrine,
however, the experience of every cook will disprove; for if the boiling
be long continued, the fibres of the meat will alone remain, and so far
from becoming more soft and pulpy, they will become dry and juiceless.
If indeed the boiling point of the water be artificially increased above
212°, by pressure applied to the surface of the liquid, the fibres may
be reduced to a pulp, quite homogeneous. When this is done by Papin’s
digester, or by any other apparatus of the same kind, and when the
process under such circumstances is long continued, the hardest bones
may be converted into jelly.
It is only by boiling that the more gelatinous parts of flesh can be
completely extracted unaltered from such parts as are cartilaginous,
ligamentous, or tendinous.
COMPARISON OF THE CHEMICAL CHANGES PRODUCED ON ANIMAL AND VEGETABLE
FOOD, IN THE DIFFERENT PROCESSES OF COOKERY.
The principal operations of cookery which we have just examined and
explained, all agree in this, that they effect some chemical change on
the materials operated upon, by which they are rendered more digestible,
more wholesome, and consequently more nutritive.
In such of the operations as are performed by the direct application of
heat to the flesh of animals, namely, roasting, baking, frying, and
broiling, the meat loses the vapid and nauseous taste and odour which it
possesses in a raw state, and becomes savoury, juicy, and grateful to
the taste. These effects arise from the development of the gelatine and
osmazome from the smaller vessels, and their being rendered soluble;
while, at the same time a portion of the fat is liquified, and combines
with them after they are disengaged.
The fibres again, on the surface of the meat, are partly scorched, and
form a crust, which, except in the interstices of the corrugations, is
impermeable, and consequently prevents the savoury gravy that is
disengaged from the fibres from oozing out or becoming evaporated. It is
thus only disengaged from its chemical union with the fibres, and
remains mechanically united with them in the meat, after it is cooked,
as we see upon cutting into the fibrous portion.
The effect produced on the fat is somewhat different. The direct
application of fire to this portion of the meat soon melts part of the
substance, and raises it to the boiling point, or nearly so; the water
which it contains is consequently given off in the form of steam, and it
carries with it a quantity of osmazome. It is this which occasions the
peculiar odour that arises from meat while roasting.
The vapid taste is also corrected by the empyreuma, combined with a
minute quantity of ammonia, which is soon developed on the surface of
the fat, by the partial charring--not of the fat itself, but of the
cellular membrane in which it is enveloped. This structure may easily be
perceived on a slight examination of a piece of recent fat; all the
membranous or skinny portions being only the receptacles or nests for
the fat itself. And since these membranes are for the most part
exceedingly thin and easily ruptured, and since heat increases the
volume of the fat which they contain, the application of heat in
roasting or broiling will soon make all the membranes burst which are
within its influence, and thus give a free passage for the juices to
unite with each other.
There is, according to these statements, but little loss of the
substance of meat when roasted or broiled, and the chemical changes
produced are so slight, that nearly all its nutritive elements must be
preserved and concentrated in the cooked meat.
When there is a watery medium used, through which heat is applied to
animal food, as for example, in the process of stewing or boiling, a
portion of the fat, gelatine, and osmazome, is dissolved, and mixes
with the water. Nutritive matter is consequently lost, or, at least, it
is transferred from the meat to the broth or soup.
In the operation of _stewing_ there is less of this transfer made; and,
besides, as the medium is scarcely kept at a boiling heat, less of the
nutritive juices are dissolved. When, however, the broth or gravy in
which meat is _boiled_ is made use of, as well as the meat itself,
boiling is the most economical practice; for though nothing be added
except the water, this itself, if it contains no nourishment, at least
fills the stomach, and serves to diffuse more widely the nutritive
juices of the meat which it holds in solution or in mixture.
But though boiling be thus the most economical practice, it is not
always to the taste of individuals, or even of whole nations to use the
broth or soup. The English and Irish, for example, rarely follow this
practice, while the Scots, French, and Germans, prefer it to all other
modes of cooking. In general, then, it should seem, that roasting as it
is the simplest, is also the best mode of rendering the flesh of animals
fit for human food. Roasted meat is wholesome and highly nourishing; and
when there is not too much of the empyreumatic crust formed, it is for
the most part easily digested. In these respects, broiled meat differs
little from such as is roasted. What is fried is always less tender. It
is often found that roasted or broiled meat sits more easily on the
stomach, and is sooner digested by those whose digestive organs are
feeble or diseased, than fried or boiled meat, or broths and stews.
The effects of the processes of cookery on vegetable substances, though
usually very slight and simple, are in some instances both striking and
unexpected. For example, some sorts of vegetables are extremely acrid
and even poisonous in their crude state, and altogether unfit for human
food; yet, by simply boiling them in water, they become bland, sweet,
and wholesome. Several species of _arum_ (cuckoo-pint), which are very
acrid, and would be dangerous to use raw, become quite palatable
pot-herbs when boiled. Their acrimony must reside in a very volatile
principle, which, during the boiling, makes its escape, or is chemically
altered; but the nature of this principle has not yet been accurately
investigated by chemists. A more familiar example than this is found in
onions, leeks, and garlick, whose acrimony and strong odour can be
almost destroyed, or rather driven off by a sufficiently long
application of heat, either directly, or through the medium of water.
Many other instances could be given, but we shall content ourselves with
one more.
Every body knows that potatoes, in a raw state, are nauseous and
unpalatable. It is not, perhaps, so generally known that the potatoe,
(_solanum tuberosum_,) belongs to the night-shade genus of plants, which
are all more or less poisonous. If potatoes were used raw, in any
quantity, they would be deleterious to man; nor does it disprove this
that cattle eat them with impunity, as sheep and goats eat plants much
more strongly poisonous to man, such as hemlockdropwort, [_oenanthe
crocata_;] and waterhemlock, [_phelandrium aquaticum_].
By boiling or roasting, however, all the unpalatable and all the
unwholesome qualities of the potatoe are changed, and it becomes
farinaceous, wholesome, digestible, and highly nutritious. Yet, although
this change is remarkable, and could scarcely have been anticipated,
very little is lost and nothing is added to the potatoe by either
roasting or boiling, yet its immediate constituent parts have evidently
suffered a very great chemical alteration, chiefly, in consequence it
should seem, from the farinaceous substance being acted on by water.
Vegetables, when used as food, are most commonly boiled, and seldom
baked or roasted. Salads, indeed, are eaten raw, without any application
of heat. The chemical action of heat on pot-herbs, on esculent roots,
and leguminous seeds, does not appear to be confined to the mere
softening of their fibres, or to the solution or coagulation of some of
their juices and component parts; for we have just now seen that their
flavour, and other sensible qualities, as well as their texture, suffer
a remarkable chemical change, which greatly improves their alimentary
properties.
In the cooking of vegetables, saccharine matter is often formed, or
mucilage and jelly extracted; and the whole substance is on that account
rendered more palatable, wholesome, and nourishing. These effects are
very well exemplified in the changes which take place in flour when
converted into bread;[24] which differs materially from flour paste,
insomuch that the constituent parts of the unbaked dough can no longer
be separated by the processes employed in chemical analysis.
[24] A treatise on the _art_ of making good and _wholesome_ bread of
wheat, oats, rye, barley, and other farinaceous grain, exhibiting the
alimentary properties and chemical constitution of different kinds of
bread corn, and of the various substitutes used for bread, in
different parts of the world, p. 58, 1821.
Vegetable substances are most commonly boiled or baked; or, if
occasionly fried or roasted, there is always much water present, which
prevents the greater action of the fire from penetrating below the
surface. The universal effect of cookery by boiling upon vegetable
substances, is to dissolve in the water some of their constituents, such
as the mucilage and starch, and to render those that are not properly
soluble, as the gluten and fibre, softer and more pulpy.