EXPERIMENT 86: GROWTH OF MOLDS ON OTHER FOODS.—Place a piece of cheese and a piece of meat on separate saucers and cover each with a glass dish. After two days examine. Have molds grown upon these foods? Account for the growth of molds upon these foods when no moisture was added to them. Devise a method for keeping cheese free from mold. Give the reasons for your method.
EXPERIMENT 87: GROWTH OF MOLD UPON WOOD.—Soak a bit of wood in water for at least 15 minutes. Cover it with an earthen dish and let it stand at room temperature for several days. Examine. Have molds grown upon the wood? What has caused the molds to grow upon the wood? From this give directions for the care of the wooden part of the dasher of an ice cream freezer. Draw conclusions concerning the care of pastry and bread boards and butter paddles after scrubbing. Draw conclusions concerning the scrubbing, drying, and airing of wooden floors.
EXPERIMENT 88: GROWTH OF MOLDS UPON CLOTH.—Sprinkle a bit of cloth with water. Cover with an earthen dish. Let stand a few days at room temperature. Examine. Have molds (mildew) grown upon the cloth? What caused the molds to grow? From this draw a conclusion concerning the care of washed clothes, wet dish-cloths, towels, and wash-cloths.
EXPERIMENT 89: CONTAMINATION OF FRESH FOOD BY MEANS OF MOLDY FOOD.—Dip a piece of bread in water and place it on a saucer. With a knitting needle, place bits of mold at several points on the surface of the bread. Cover with a glass dish. After several days examine. At what points on the bread have the molds started to grow? What conclusion can you draw from this concerning the placing of moldy food with fresh food? When fruit is falling to the ground, tell how an orchard should be cared for. Explain.
The following experiments show the growth of bacteria on food:
EXPERIMENT 90: GROWTH OF BACTERIA.—Into test tubes put one of the following foods: (1) bit of uncooked meat; (2) small quantity of egg; (3) piece of bread; (4) crushed peas or beans; (5) sugar or syrup. Add a little water to each tube. Set aside in a warm place. After several days, examine. What change in appearance do you note? What has caused the foods to spoil?
EXPERIMENT 91: EFFECT OF BOILING ON THE GROWTH OF BACTERIA.—Place a little chopped meat in two test tubes. Add lukewarm water to each. Boil the contents of one of the tubes for several minutes. Set both aside. After 24 hours, examine. What difference is there in the condition of the meat in each tube? Explain this difference. From the result of this Experiment draw conclusions regarding the boiling of food to prevent spoiling.
EXPERIMENT 92: EFFECT OF PRESERVATIVES ON THE GROWTH OF BACTERIA.—Beat slightly an egg white. Add to it 1/2 cupful of water. Pour a little of the diluted egg white into four test tubes. To three of the test tubes add one of the following: (1) salt; (2) sugar; (3) vinegar. Put all of the tubes in a warm place. After several days, examine. What is the condition of the egg white in each tube? Explain. Draw inferences regarding the use of "safe" preservatives to prevent foods from spoiling.
THE PRINCIPLES OF PRESERVING FOOD.—Food may be preserved by opposing the growth of microorganisms or by destroying them. Low temperatures, certain preservatives, and drying destroy microorganisms or retard their growth.
[Illustration: From Household Bacteriology, by Buchanan