These agents are of
three classes, namely, _organic, physical_, and _chemical_. The organic
agent is the oldest recognized leavening material, it being the one that
is used in the making of yeast breads; but as a complete discussion of
this class of leavening agents is given in _Bread_ and as it is not
employed in the making of hot breads, no consideration need be given to
it here. Physical leavening is accomplished by the incorporation of air
into a mixture or by the expansion of the water into steam, and chemical
leavening agents are the most modern and accurate of all the agents that
have been devised for the quick rising of flour mixtures.
PHYSICAL LEAVENING
4. PHYSICAL LEAVENING consists in aerating, or incorporating gas or air
into, a mixture that is to be baked, and it is based on the principle
that air or gas expands, or increases in volume, when heated. It is
definitely known that when air is incorporated into dough and then
heated, the air increases 1/273 of its own volume for each degree that
the temperature is increased. For instance, if the temperature of an
aerated mixture is 65 degrees Fahrenheit when it is put into the oven,
the air or gas will have doubled in volume by the time it has reached
338 degrees Fahrenheit. Thus, the success of aerated bread depends to
some extent on the temperature of the mixture when it goes into the
oven.
Pages:
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296