The San Francisco call., 1899-12-23
XII. THE SCIENCE OF COOKERY

| lStry, physics, botany and DacterlOlOBy
all play their part in the preparation OF
| the food we eat.
We can hardly overestimate the impor-
tance OF chemistry in the kitchen, but
hitherto IN the study OF foods IT often has
been given an undue prominence While
other sciences have been neglected. Or
ganic chemistry is so complex that as
yet the best chemists are unwilling to
| give US many positive statements about
foods and the Transformation which Ihcy
undergo in digestion, and while a single
| food material may be studied with COM
| parative case, complications arise from
Many changes once attributed TO chemi-
cal action are now found to be caused by
| bacteria.
Many household processes can be used
| to illustrate science study in the schools
and the principles which are learned there
may be applied at home. Physics teaches
US the laws OF fire and water upon which
changes Of matter mainly depend. With
out heat and moisture cookery would be
impossible, and the laws that rule those
forces are the same in the kitchen as
elsewhere. We must learn that heated
matter expands: that substances In fine
particles or in solution change form more
rapidly than they could do otherwise;
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place under the influence OF heat; that at
sea level II boils at a fixed temperature
| C212 degrees Fahrenheit or 100 degrees
| centigrade) and cannot then be made hot
ter under ordinary conditions.
The upward tendency of heated air
gives the clew to the most mysterious ar
rangements OF dampers and draughts in
kitchen range. The contraction and ex-
pansion OF different metals and their
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bearing upon the chemical changes which
| take place in foods cooked in different
utensils.
Bright now tin reflects heat and is best
suited TO baking In gas and kerosene
ovens where the heat below is intense;
the blackened tin or sheet iron absorbs
heat and should be used where an oven
does not bake we'll at the bottom. A
knowledge of the range OF temperature
required for cooking common foods Is
indispensable to the housekeeper who
would feed her family properly.
The mechanical effects of heat and cold
are also important. Gelatin sometimes
perplexes the cook by refusing TO harden
properly. This may be due to some fer
ment or bacterial action. but is more often
the result OF a too high degree OF tenn
perature. Once try this experiment and
the thing is plain: Strain a coffee or lem
on jelly into several small molds. leave
one in a warm place, put another IN a
pan of cold water, a third in a dish Of
cracked ice and surround a fourth with
| ice and salt. The last hardens rapidly and
| II left long enough will freeze, as the
temperature Of the ice and salt will be
considerably below the freezing point.
The others will cool more slowly. though
the first will not begin TO harden for a
| long time.
The use of oil in salad dressings and OF
butter and kindred fats in pastry and
cakes is also subject to the laws OF heat
and cold. ANY dough to be rolled thin.
| like cookies or piecrust. should be very
cold. A thermometer with wide range OF
temperature is a useful kitchen appliance.
Economic botany teaches us the times
and seasons OF plant foods. and the like
ness OF members of the same families Of
plants. Molds and yeasts, their habits
and effects upon food substances, must
be studied by the methods Of the botanist
Some knowledge of the new science Of
bacteriology is essential for the guardian
of cellar and refrigerator. This science
is associated not only with the ever-pres-
ent dust and all the danger arising from
IL but also with the preparation and pres
ervation of foods. The souring Of milk.
the flavor of butter, the ripening Of
cheese. fruit cakes and mince pies, the
spelling of canned goods and the decay
of fruits, vegetables and meats are all
due primarily 10 the micro-organisms
known as bacteria.
Bringing his knowledge gained through
many patient experiments to the aid OF
the housewife, the bacteriologist tells her
that clean foods keep better than dirty
ones; that sterilization, which consists Of
subjecting any substance for a sufficient
time TO the temperature OF boiling water
or. better still, TO higher point by dry
heat or superheated steam, will render
suspected water or food comparatively
harmless.
Because most bacteria do their work
more easily in liquids. concentrated or
drier substances are more easily pre-
served. Fruit juices in the form Of jellies
rendered solid with sugar require less
protection than fruits with liquid juices:
the latter must not only be thoroughly
sterilized but also kept in air-tight jars.
The consumer sometimes objects to the
change in form and color often caused by
a high degree of heat, hence the profess
sonal food packers frequently use certain
chemicals 10 retard bacterial action. The
use of preservatlves and chemical colors
and favors is a serious question at the
present time. Few housekeepers have the
time, knowledge or appliances for food
analysis but all can take suspected arti-
cIes TO the local or State Board OF Health.
Ii takes a well trained chemist TO detect
fraud, and legal authority 10 fight IL.
Fortunately. most of the common adul-
teration of food is what is termed sophis-
tication, or the substitution OF a harmless,
cheap substance for a more costly one.
every purchaser should be sufficiently
familiar with food values TO recognize
the impossibility of selling the real arti-
clos az The prices for which they are
sometimes offered.
The principal chemical changes which
take place in food while cooking may be
described in few words. but before this
can be done the foods must be classified
The substances in all foods may be
grouped under five divisions-water. min
cral matter, proteid. fat and carbohy-
drates These substances are combined
in varying proportions in foods or nat
ural form as well as in the compounds OF
! the cook.
Charts have been published by the
United States Government which explain
this classification and show the compost
ton of common foods
Water is the universal carrier OF solid
substances throughout the human system
as IL is over the surface OF the earth.
Mineral matter Is found in all foods in
minute quantities and is essential for
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