(Study pages 29-55)

If the Food Course is being taken, some of the experiments here suggested might better be postponed until the lessons on Principles of Cookery or Food and Dietetics.

Starch

The blue color produced by a tincture of iodine (obtained at the drug store) on the faintest trace of starch is a very delicate test for starch. Cooked starch shows the test much better than uncooked. Note that the blue color is destroyed by heat, but appears again when the test is cool. Test various foods - grains, vegetables, fruits, and nuts for starch.

The conversion of starch into dextrin may be shown by heating a little flour or corn starch in a hot oven for half an hour or so, or until it becomes a deep yellow color. Dissolve in a little cold water, filter out the unchanged starch by pouring through absorbent cotton in a funnel; test the filtered liquid to see if there is still any unchanged starch in it. Add double the quantity of alcohol to a part of the liquid. The dextrin will be precipitated, i. e., thrown out of solution and will settle as a fine powder,because dextrin is not soluble in alcohol. The water solution should be concentrated by boiling if much is used.

That the starch is changed by heating with butter or other fat may be shown by adding two teaspoonfuls of flour to one teaspoonful of very hot butter, stirring for some time. Remove a drop on a piece of white paper and test it with tincture of iodine.

Make starch paste by mixing a quarter of a teaspoonful of laundry or corn starch with a spoonful of water and adding it to a cup of boiling water and boil. To about half a glass of this when it has cooled to body temperature (ioo° F) add a half teaspoonful of saliva. Keep the mixture warm (not hot) for some time by placing it in warm water. From time to time test small portions with iodine solution as it grows clearer. Add saliva to a portion of hot starch; to a cold portion testing as before.

Gluten

May be the gluten separates from flour as described on page 49, or better as described in "Food and Dietetics" page 41. Bake part of it in an oven.

Experiments with other proteids also described on pages 41 and 43 of "Food and Dietetics."

Experiments with yeast described on page 45 of "Household Bacteriology," Part I.

"Digestion is Synonymous with Solution"

This statement is made on page 35. To show the relation of the length of time required to make a solution, take two equal portions of any crystals, such as washing soda or alum, and pulverize one portion. Stir each in a glass of water and observe the time for each in dissolving. Note that the time required for complete solution is determined by the largest crystal.

This experiment shows how important a part of digestion chewing is and that the teeth are primarily digestive organs.

Cooking Meat

See experiment on pages 50 and 51.

Mineral Matter - Gelatin See experiments on page 53.

References: Chemistry of Cookery, by Mattieu Williams Pages 19-31. Albumen. ($1.50, postage 16c.) Chemistry of Daily Life, by Lassar-Conn. Pages 56-66. Digestion of Food. ($1.50, postage 10c.)

(Select and send to the School a composite set of answers to Test Questions on Part I, and report on supplemental work and experiments.)