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  Honey—Adulterations of—General observations—Cane sugar—Commercial glucose syrup—Gelatin.   Maple Syrup—Adulterations of—General examination—Glucose. CHAPTER IX   Spices 51   Mustard—Adulterations of—Flour—Coloring matter—Turmeric—Martius yellow or analogous coal-tar coloring matter—Cayenne pepper.   Pepper—Adulterations of—General test—Ground olive stones—Cayenne pepper. CHAPTER X   Vinegar 55   Adulterations of—Preparation of sample—General observations—Free mineral acids—General tests—Sulfuric acid—Hydrochloric acid (free)—Malic acid—Coloring matter—Caramel—Coal-tar colors—In wine vinegar—Free tartaric acid—In wine vinegar. CHAPTER XI   Fats and Oils 60   Lard—Adulterations of—Cottonseed oil—Cottonseed stearin—Beef stearin.   Olive Oil—Adulterations of—General test—Cottonseed oil—Peanut oil—Sesame oil—Rape oil. CHAPTER XII   Beverages 65   Coffee—Adulterations of—General test—Coloring matter—Imitation coffee beans—Chicory.   Tea—Adulterations of—Foreign leaves—Exhausted tea leaves—Lie tea—Facing—Catechu.

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PURE FOOD TESTS

CHAPTER I
DAIRY PRODUCTS

MILK

Milk is adulterated by watering, removing the cream or by adding some foreign substance. Formaldehyde, boric acid or salicylic acid may be added to preserve the milk. Annatto, caramel or some coal-tar dye is added, sometimes to improve the color of the milk, and at other times to cover up traces of watering. Gelatin and starch are added for the same purpose, though they are not frequently used.

ARTIFICIAL COLORING MATTER

Annatto

Add acid sodium carbonate to a sample of the milk until it shows a slight alkaline reaction. Immerse a piece of filter-paper and leave it in for 12 or 15 hours. If annatto is present, there will be a reddish-yellow stain on the paper.

Caramel

Leach’s Method.—Warm 150 cc. of the sample and add 5 cc. of acetic acid, then continue heating it nearly to the boiling point, stirring while it is being heated. Separate the curd by gathering it with the stirring rod or by pouring through a sieve. Press out all the whey from the curd and macerate the latter for several hours (10 to 12 hours) in 50 cc. of ether. It is best to do this in a tightly corked flask, shaking it frequently. If the milk was uncolored or colored with annatto the curd when thus treated will be white. If the curd is a dull brown color caramel was probably used to color the milk. Confirm its presence by shaking a portion of the curd with concentrated hydrochloric acid (sp. gr. 1.20) and gently heating. If the acid solution turns blue while the curd does not change its color, caramel was used to color the milk. (Remember that the ether-extracted curd must be brown.)

Coal Tar Colors

Lythgoe’s Method.—Mix in a porcelain vessel about 15 cc. each of the sample of milk and hydrochloric acid (sp. gr. 1.20) and break up the curd into coarse lumps by shaking gently. If an azo-color was used to color the milk this curd will be pink, but the curd of normal milk will be white or yellowish.

Starch

The presence of starch in milk may be detected by heating a small quantity of the milk to boiling. When it has cooled add a drop of iodin in potassium iodid, and if starch is present there will be a blue coloration.

Gelatin

A. W. Stokes’ Method.—Dissolve 1 part by weight of mercury in 2 parts of nitric acid (sp. gr. 1.42). Add 24 times this volume of water. Mix equal volumes (about 10 cc.) of this reagent and the milk or cream, shake well and add 20 cc. of water. Shake again and, after standing 5 minutes, filter. When a great quantity of gelatin is present the filtrate will be opalescent instead of perfectly clear. To a little of this filtrate in a test tube add the same volume of a saturated aqueous solution of picric acid. If much gelatin is present a yellow precipitate is produced, smaller amounts produce a cloudiness. If the filtrate is perfectly clear gelatin is absent and picric acid may be added without producing any noticeable effect.

PRESERVATIVES

Formaldehyde

Hehner’s Sulfuric Acid Test.—Put 10 cc. of the suspected milk in a wide test tube and pour carefully down the side of the inclined tube about 5 cc. commercial sulfuric acid so that it forms a separate layer at the bottom. A violet coloration at the union of the two liquids indicates the presence of formaldehyde. If the commercial acid is not available, the pure acid may be used, but a few drops of ferric chloride must be added. Sometimes the charring effect of the acid makes it advisable to use the following test:

Hydrochloric Acid Test.—2 cc. of 10 per cent ferric chloride is added to one liter of commercial hydrochloric acid sp. gr. 1.2 (or any quantity in this proportion). To 10 cc. of this mixture add 10 cc. of the milk to be tested. Heat the mixture slowly nearly to the boiling point, in an evaporating dish, but agitating it all the while to prevent the curd collecting in one mass. If formaldehyde is present, there will be a violet coloration. It is said that by this test as small a quantity of formaldehyde as 1 part in 250,000 parts of milk can be detected. It is not so sensitive in sour milk.

Boric Acid

Turmeric Paper Test.—Incinerate some of the milk, and acidulate the ash with a very few drops of dilute hydrochloric acid and afterwards dissolve it in a few drops of water. Place a strip of turmeric