Blackberry juice, diluted with water. Infusion of tea in cold water) the solutions to be of equal Infusion of tea in hot water ) strength. Infusion of coffee in cold water ) the solutions to be of equal Infusion of coffee in hot water ) strength. Solution of cocoa. Add to each test tube a few drops of a solution of iron chloride or any soluble salt of iron. A black color or precipitate indicates the presence of tannin. II Effect of Tannin Into SIX test tubes pour about an inch of the following, respectively : Hydrated and dissolved gelatine. A solution of pepsin. White of egg. A solution of pancreatine. A solution of Liebig's extract. Some clear saliva. Add to each test tube a few drops of a strong solution of tannin. Note in which cases, and to what extent, precipitation takes place. Determine by the use of Millon's reagent whether protein bodies are present in the solutions of pepsin and pancreatine, and in the saliva. Millon's reagent is the test used to demonstrate the presence of small amounts of proteid in any substance, QUESTIONS 199 TOPICS FOR STUDY OR DISCUSSION 1. The history of tea, coffee, and chocolate. 2. The chief varieties of coffee; the great coffee planta- tions of the world; the manufacturing processes used in the preparation of coffee for the market. 3. The chief tea-producing countries. The effect on tea of climate, soil, and method of manufacture. 4. Cocoa, and the by-products of its manufacture — cocoa shells, cocoa butter, etc. 5. The chemical composition of coffee, tea, and choco- late. The difference between the cocoa and chocolate of commerce. 6. The effect on digestion of tea, coffee, and cocoa. The effect of these beverages on the nerves. 7. Common adulterants of tea, coffee, and chocolate. Food laws relating to these substances. 8. Races and nations which favor the use of each of the beverages studied. QUESTIONS 1. Which of the substances tested in Experiment I do you infer contains the largest amount of tannin? Which the smallest? 2. What fallacy is involved in prohibiting the use of tea and coffee and permitting the use of grape juice, black- berries, etc., in the diet? 3. On what grounds might tea and coffee be forbidden and other foods containing tannin be allowed? 4. Has the method of making tea and coffee any effect on the amount of tannin extracted? 5. Which would be easier of digestion, a gelatine jelly flavored with coffee, or one flavored with orange juice? Why? What is the effect of tannin on protein foods? on the digestive juices? 6. Compare the effect of drinking tea or coffee at the beginning of a meal, during the meal, or at its close. 7. What do you think was the cause of the discoloration of the potato in the work of Chapter II, page 10? 200 PRINCIPLES OF FOOD PREPARATION References Bailey. Sanitary and Applied Chemistry, Chap. XXII. Church. Food, Part IV. Hutchison. Food and Dietetics, Chap. XVIII. Lassar-Cohn. Chemistry in Daily Life, see Index. Lusk. The Science of Nutrition, see Index. Snyder. Human Foods, Chap. XIV. Thompson. Food and Dietetics, see Index. CHAPTER XX CAKES, PIES, AND PtJDDINGS

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Blackberry juice, diluted with water. Infusion of tea in cold water) the solutions to be of equal Infusion of tea in hot water ) strength. Infusion of coffee in cold water ) the solutions to be of equal Infusion of coffee in hot water ) strength. Solution of cocoa. Add to each test tube a few drops of a solution of iron chloride or any soluble salt of iron. A black color or precipitate indicates the presence of tannin. Effect of Tannin Into SIX test tubes pour about an inch of the following, respectively : Hydrated and dissolved gelatine. A solution of pepsin. White of egg. A solution of pancreatine. A solution of Liebig's extract. Some clear saliva. Add to each test tube a few drops of a strong solution of tannin. Note in which cases, and to what extent, precipitation takes place. Determine by the use of Millon's reagent whether protein bodies are present in the solutions of pepsin and pancreatine, and in the saliva. Millon's reagent is the test used to demonstrate the presence of small amounts of proteid in any substance, 1. The history of tea, coffee, and chocolate. 2. The chief varieties of coffee; the great coffee plantations of the world; the manufacturing processes used in the preparation of coffee for the market. 3. The chief tea-producing countries. The effect on tea of climate, soil, and method of manufacture. 4. Cocoa, and the by-products of its manufacture — cocoa shells, cocoa butter, etc. 5. The chemical composition of coffee, tea, and chocolate. The difference between the cocoa and chocolate of commerce. 6. The effect on digestion of tea, coffee, and cocoa. The effect of these beverages on the nerves. 7. Common adulterants of tea, coffee, and chocolate. Food laws relating to these substances. 8. Races and nations which favor the use of each of the beverages studied. 1. Which of the substances tested in Experiment I do you infer contains the largest amount of tannin? Which the smallest? 2. What fallacy is involved in prohibiting the use of tea and coffee and permitting the use of grape juice, blackberries, etc., in the diet? 3. On what grounds might tea and coffee be forbidden and other foods containing tannin be allowed? 4. Has the method of making tea and coffee any effect on the amount of tannin extracted? 5. Which would be easier of digestion, a gelatine jelly flavored with coffee, or one flavored with orange juice? Why? What is the effect of tannin on protein foods? on the digestive juices? 6. Compare the effect of drinking tea or coffee at the beginning of a meal, during the meal, or at its close. 7. What do you think was the cause of the discoloration of the potato in the work of Chapter II, page 10? References Bailey. Sanitary and Applied Chemistry, Chap. XXII. Church. Food, Part IV. Hutchison. Food and Dietetics, Chap. XVIII. Lassar-Cohn. Chemistry in Daily Life, see Index. Lusk. The Science of Nutrition, see Index. Snyder. Human Foods, Chap. XIV. Thompson. Food and Dietetics, see Index. CHAPTER XX

Principles of food preparation