Part 73 (1/2)

REVIEW--MEAL COOKING

MENU

Rolled Beef Steak Stuffed Baked Potato Drop Biscuits

See Lesson XIV for suggestions regarding the preparation of the lesson.

LESSON Cx.x.xIV

HOME PROJECTS [Footnote 108: See Lesson IX.]

SUGGESTIONS FOR HOME WORK.--Plan and cook meals.

From the Table of 100-Calorie Portions estimate the fuel value of the meals you prepare.

SUGGESTED AIMS: To compare the fuel value of the meals with the energy requirements secured in answering the _Questions_ in Lesson Cx.x.xI. To use these comparisons as a basis on which to plan meals more nearly approaching the desired energy requirements.

DIVISION THIRTEEN

YEAST BREADS: STIFF DOUGHS

LESSON Cx.x.xV

YEAST--LOAF BREAD

EXPERIMENT 77: CONDITIONS FOR GROWTH OF THE YEAST PLANT.--(_a_) Mix 1 tablespoonful of flour, 1 tablespoonful of sugar, 3/4 cake compressed yeast, and 5 tablespoonfuls of cold water. Put 1 tablespoonful of the mixture in a test tube and mark the tube ”_a_.” Fill the tube nearly full of lukewarm water and stand in a warm place for 15 minutes. Examine, noting especially the appearance at the top of the test tube. What kind of substance (gas, liquid, or solid) has been formed by the growth of the yeast plants?

(_b_) Put 1 teaspoonful of the yeast mixture in a test tube, and fill nearly full of boiling water. Label it ”_b_” and after 15 minutes examine. Is there any change in the contents of the tube? What has happened to the yeast plants?

(_c_) Put 1 teaspoonful of the yeast mixture in a test tube, fill nearly full of cold water, and label it ”_c_.” Surround it with cracked ice or, if the weather is cold, place it out of doors. After 15 minutes examine. Is there any change in the contents of the tube? Why do not the yeast plants grow?

(_d_) Surround the tube marked ”_c_” with lukewarm water and stand in a warm place. After 15 minutes examine. Are the yeast plants growing? Does freezing kill yeast plants?

(_e_) Mix 1/8 cake yeast with a little lukewarm water. Stand in a warm place and after 15 minutes examine. Will yeast grow in water alone?

(_f_) Mix 1/8 cake yeast, 1 tablespoonful of sugar, and a little lukewarm water. Set aside in a warm place so that the yeast plants may grow. Then examine under the microscope. Are there any budding yeast cells? Make a drawing of the plants as they appear under the microscope.

Draw at least two practical conclusions from these experiments as to the use and care of yeast for bread making

[Ill.u.s.tration: From _Farmers' Bulletin 398_ FIGURE 86--GROWING YEAST PLANTS]

PROPERTIES OF YEAST.--Yeast consists of a ma.s.s of microscopic plants (see Figure 86). When placed under proper conditions these plants grow rapidly, and in so doing they separate the sugar that exists in flour into carbon dioxide and alcohol. The carbon dioxide lightens dough. The alcohol pa.s.ses off as vapor in baking.

Plants need moisture, warmth, light, and the food that is furnished by the air and soil for their growth. Yeast plants require all of these except light. They are not green plants, hence they need no light. Moisture is obtained from the water, milk, or other liquids used in bread dough. Yeast thrives at a temperature of 90 degrees F. It is killed by a temperature above 130 degrees F. Hence the yeast is mixed with lukewarm water. The other liquids that are added to it are of the same temperature. Also, the dough is placed in a warm place while it is rising, or while the yeast plants are growing. The food required for the rapid growth of the yeast is obtained from the protein and carbohydrates in the flour.

_Compressed yeast cakes_ which are wrapped in tinfoil and received fresh at the market every day or two are the most satisfactory to use.