C. Whipping Cream.

1. Put empty test bottle c on the scales and proceed as for ordinary cream. 9 grams may also be used and the per cent multiplied by 2. What is the per cent of butter fat in

whipping cream?

D. Skimmed Milk.

1. Use test bottle d with two necks, the larger to deliver materials into the smaller, to read the fractions of per cents as the fat rises. What is the per cent of butter fat in skimmed milk?

E. Canned Milk.

1. Pour out entire contents of the can and mix well.

2. Weigh 9 grams into test bottle a. Add 9 cc. of water. Mix thoroughly in the test bottle. Add enough concentrated sulfuric acid to turn the contents dark brown. Proceed as before.

3. If the canned milk is sweetened special precautions may be necessary. (See Leach.) What is the per cent of

butter fat in the milk tested?

REFERENCES:

EXPERIMENT 49

Beverages-Tea, Coffee, Cocoa

1. Olsen, Pure Food, pages 110-112.

2. Sherman, Food Products, pages 465-466.

3. Bailey, Sanitary and Applied Chemistry, Chapter XXII.

MATERIALS. Tea, coffee, chocolate, cocoa, ferric chloride, chloroform, iodine solution, sulfuric acid, Fehling's solution, Millon's reagent.

APPARATUS. Beakers, funnels, filter paper, test tubes, graduate, teaspoons, tablespoons, separatory funnel.

A. Tannin in Tea.

Tea

1. Boil 50 cc. of water in a beaker. Add a level teaspoonful of tea and remove from the flame at once. Allow it to stand just five minutes, then filter. Place 5 cc. of the filtrate in a test tube, add 1 cc. of ferric chloride, 25 cc. of water from your graduate. Stir. Keep this test for comparison. What is the dark precipitate?

2. To 50 cc. of boiling water in the beaker add a level teaspoonful of the same tea and boil for five minutes, then filter. Place 5 cc. of the filtrate in a test tube of the same size as that used in A, 1. Add 1 cc. of ferric chloride solution and then 25 cc. of water. Stir. Compare the intensity of color with that of A, 1 and explain. What is the best method of preparing tea? Why?

B. Theine or Caffeine in Tea. (Instructor's Experiment.)

1. Boil three teaspoonfuls of good tea in 100 cc. of water for five minutes, filter, cool, and add 20 cc. of chloroform. Place the mixture in a separatory funnel, shake well for one minute, and then allow the chloroform to settle. Draw it off into a clean beaker and allow it to evaporate at room temperature. Note the pleasant smelling, silky crystals of theine or caffeine. (They are the same chemically.)

C. Questions on Tea.

1. How is green tea prepared for market? Name some varieties of green tea on the market.

2. How does black tea differ from green tea? Name some varieties of black tea on the market.

3. Which contains more tannin, the black or the green tea? Give the reason for your answer.

D. Tannin in Coffee.

Coffee

1. To 200 cc. of cold water in your large beaker add one tablespoonful of well-ground coffee. Slowly bring this to the boiling point and boil for three minutes. Filter. Treat 5 cc. of the filtrate as in A, 1. Keep the test for comparison. 2. Repeat D, 1, but boil for fifteen minutes. Filter and treat 5 cc. of the filtrate as in A, 1. Compare the intensity of color with that of D, 1 and explain. What is the best method of preparing coffee? Why?

E. Caffeine or Theine in Coffee.

(Instructor's Experiment.)

1. Add two tablespoonfuls of coffee to 250 cc. of cold water. Bring slowly to the boiling point and boil five minutes. Filter. Cool the filtrate and repeat B, 1. Note the pleasant smelling, silky crystals of caffeine or theine. What is the effect of caffeine or theine upon the human system?

F. Questions on Coffee.

1. How is coffee prepared for market?

2. Why is the coffee bean roasted?

Chocolate and Cocoa

G. Fat in Chocolate and Cocoa.

1. Test both chocolate and cocoa for fat by treating 10 grams of each with 50 cc. of gasoline. Shake well and filter through a dry filter. Allow the gasoline to evaporate. Which contains the most fat?

H. Questions on Chocolate and Cocoa.

1. How is chocolate prepared from the bean for market? 2. How is the beverage made from chocolate?

3. How does the preparation of cocoa on the market differ from that of chocolate?

4. Which beverage is the more nourishing, chocolate or cocoa? Why?

5. For what other purposes are chocolate and cocoa used?

Note: If possible visit a manufacturing house where chocolate and cocoa are prepared from the unroasted beans.

XIII. FOOD ADULTERANTS

The most important food adulterants may be divided into three classes: (1) Substitutes. (2) Artificial Coloring. (3) Preservatives.

REFERENCES:

1. Leach, Food Inspection and Analysis.

2. E. M. Bruce, Detection of the Common Food Adulterants. 3. Woodman, Food Analysis.

4. Olsen, Pure Foods.

MATERIALS.

EXPERIMENT 50

Adulterants in Milk

Milk containing borax or boric acid, another sample containing formaldehyde, limewater, hydrochloric acid, turmeric paper, ferric ammonium alum, concentrated sulfuric acid. APPARATUS. Evaporating dish, test tubes.

A. Substitutes.

1. Cream may be removed and water added until the specific gravity is that of pure whole milk. What should be the per cent of water in whole milk? How can the per cent of water in milk be determined? (See Experiment 47.)

B. Artificial Coloring.

Milk is seldom colored artificially. Annatto or turmeric might be used as in the case of butter and they would be detected in the same way.

C. Preservatives.

1. Borax and boric acid in milk may be detected as follows: Place 20 cc. of milk in an evaporating dish. Add 5 cc. of limewater. Evaporate to dryness. Continue to heat the dish till only a white residue remains. If borax or boric acid was in the milk it will be present in this ash. Dissolve the residue in 1 cc. of dilute hydrochloric acid. Dip a strip of turmeric paper in the solution and dry at 100° on a test tube of boiling water. A bright red color indicates the presence of boric acid or borax. The red color is changed to dark green by a drop of ammonium hydroxide.

If there is much borax or boric acid present, the test may be simplified. Acidify the milk with hydrochloric acid. Dip in the turmeric strip. Dry at 100° on a test tube of boiling water. A bright red color will appear.

2. Formaldehyde in milk may be detected as follows: Dissolve a crystal of ferric ammonium alum (about the size of a pea) in about 1 cc. of water. Carefully add 1 cc. of concentrated sulfuric acid. Pour this solution carefully down the side of an inclined test tube containing about 10 cc. of the milk to be tested. A violet coloration is produced at the junction of the two liquids if formaldehyde is present. Warm over the Bunsen burner if necessary.

If possible visit a large dairy or creamery and note particularly the precautions taken for the sake of cleanliness.