The biscuits thus baked, are dried in lofts over the oven till they are perfectly dry, to prevent them getting mouldy when stored for use.
One-hundred and twelve pounds of flour produce one hundred and two pounds of perfectly dry biscuits.
Leavened Bread,
Or bread made with a portion of fermented sour dough, obtained by keeping some bread dough till the acetous fermentation takes place, when it swells, rarifies, and acquires a taste somewhat sour, and rather disagreeable. This fermented dough is well worked up with some fresh dough, which is, by that mixture and moderate heat, disposed to ferment; and by this fermentation the dough is attenuated and divided, carbonic acid is extricated, which being incapable of disengaging itself from the tenaceous and solid dough, forms it into small cavities, and raises and swells it; hence, the small quantity of fermented dough which disposes the rest of the mass to ferment is called leaven.
Most of the bread used by the people in the lower walks of life in France, Germany, Holland, and other European countries, is made in this manner.
Leavened bread, therefore, differs from unleavened bread, in being fermented by means of leaven, which is nothing more than a piece of dough kept in a warm place, till it undergoes a process of fermentation, swelling, becoming spongy, and full of air bubbles, and at length disengaging an acidulous vapour, and contracting a sour taste. Leaven must, therefore, be considered as dough which has fermented and become sour, but which is still in its progress towards greater acidity.
The addition of leaven, or this species of ferment to fresh dough, produces an important change in the bread, for when a small portion of leaven is intimately mixed with a large proportion of fresh dough, it gradually causes the whole mass to ferment throughout, a quantity of carbonic acid gas is extracted from the flour, but remaining entangled by the tenacity of the mass in which it is expanded by heat, this raises the dough, and as soon as the mass has acquired a due increase of bulk from the carbonic acid gas which endeavours to escape, it is judged to be sufficiently fermented and fit for the oven, the heat of which, by driving off the water, checks the fermentation, and forms a bread full of small cavities, entirely different from the heavy, compact, viscous masses, made by baking unfermented dough.
A great deal of nicety is required in conducting this operation, for if it is continued too long, the bread will be sour, and if too short a time has been allowed for the dough to ferment and rise, it will be heavy.
Bread raised by leaven is usually made of a mixture of wheat and rye, not very accurately cleared of the bran. It is distinguished by the name of rye bread; and the mixture of these two kinds of grain is called bread-corn, in many parts of the kingdom, where it is raised on one and the same piece of ground, and passes through all the processes of reaping, thrashing, grinding, &c. A mixture of one-hundred pounds of equal parts of wheat and rye flour, produce from one-hundred and fifty-four to one-hundred and fifty-six pounds of leavened bread.