Commercial yeast is placed on the market in two forms–moist and dry. Each of these yeasts has its advantages, so that the one to select depends on the method preferred for the making of bread as well as the time that may be devoted to the preparation of this food.

Moist yeast, which is usually called compressed yeast, consists of the pure yeast culture, or growth, mixed with starch to make a sort of dough and then compressed into small cakes, the form in which it is sold. The moist condition of this kind of commercial yeast keeps the plants in an active state and permits of very rapid growth in a dough mixture. Consequently, it proves very useful for the rapid methods of making bread. It is soft, yet brittle, is of a grayish-white color, and has no odor except that of yeast.

Since the plants of compressed yeast require very little moisture to make them grow, an unfavorable, or low, temperature is needed to keep the yeast from spoiling; in fact, it is not guaranteed to remain good longer than a few days, and then only if it is kept at a temperature low enough to prevent the plants from growing. This fact makes it inadvisable to purchase compressed yeast at great distances from the source of supply, although it may be obtained by parcel post from manufacturers or dealers.

Dry yeast, the other form of commercial yeast, is made in much the same way as moist yeast, but, instead of being mixed with a small amount of starch, the yeast culture is combined with a large quantity of starch or meal and then dried. The process of drying kills off some of the plants and renders the remainder inactive; because of this, the yeast requires no special care and will keep for an indefinite period of time, facts that account for its extensive use by bread makers who are not within easy reach of the markets. However, because of the inactivity of the yeast plants, much longer time is required to produce fermentation in a bread mixture containing dry yeast than in one in which moist yeast is used. Consequently, the long processes of bread making are brought about by the use of dry yeast. If moist yeast is used for these processes, a smaller quantity is required.

Liquid Yeast.–Some bread makers are so situated that they find it difficult to obtain commercial yeast in either of its forms; but this disadvantage need not deprive them of the means of making good home-made bread, for they can prepare a very satisfactory liquid yeast themselves. To make such yeast, flour, water, and a small quantity of sugar are stirred together, and the mixture is then allowed to remain at ordinary room temperature, or 70 degrees Fahrenheit, until it is filled with bubbles. If hops are available, a few of them may be added. When such yeast is added to a sponge mixture, it will lighten the whole amount. Before the sponge is made stiff with flour, however, a little of it should be taken out, put in a covered dish, and set away in a cool, dark place for the next baking. If properly looked after in the manner explained, this yeast may be kept for about 2 weeks.

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