MILK ADULTERATION AND CONTROL. The milk supply of towns and cities has for many years been regulated by laws and ordinances, and sub jected to inspection. The objeet of this was for merly to prevent adulteration, but of recent years the inspection has often extended to the herds and stables and all that relates to the milk trade. It has conic to be realized that such fac tors as the health of the cows, hygienic condi tion of the stables, and cleanliness in the hand ling of the milk are quite as essential to pure wholesome milk as freedom f adulteration. Hence the veterinary inspection. which has been introduced in some cities, should he extended. Milk is most often tampered with by removing a part of the cream, or by diluting it with water or skim milk. Coloring matter is sometimes added to make it appear richer. but the addition of chalk. burnt sugar. or similar substanees is now rare. Preservative's, such as formaldehyde, borax, and salicylic acid, are sometimes added to prevent milk souring. Opinions differ as to the injuriousness of these preservatives, but their use is generally condemned on the ground that they are unnecessary in pure milk. and that they are a cloak for unsanitary practices in the dairy. The standards for milk adopted by different States vary from 11.5 to 13 per cent. for total solids and from 2.5 to 3.5 per cent. for fat. Milk found below these standards is held to be adul terated. A standard of 12.5 per cent. of total solids and at least 3 per cent, of fat seems fair.
Various means of testing milk as to its qual ity have been suggested from time to time. Of these the lactometer is the simplest, and has been extensively used by milk inspectors who have a large number of samples to examine daily, to detect watering or skimming. it is a form of hydrometer. which shows the specific gravity of milk upon a graduated scale. But there are so many factors that affect the specific gravity, and this may vary so much in pure milk, that the lactometer reading is only an indi cation and cannot la. relied upon as final. The most reliable and satisfactory of the simple milk tests is the Babcock test, which has come into very widespread use in the milk inspection of towns and cities. and in determining the fat con tent of milk as a basis for paying fur the prod uct at creameries. (See CREAMERY: BurrEn MAKING. ) This test is made in a special bottle
having a narrow graduated neck. A definite quantity of milk is treated in the bottle with snlphurie acid to dissolve the curd and set the fat free. The bottle is then whirled rap idly in a centrifugal apparatus for a few min utes. to aid in separating the fat hot water is added to bring the fat up into the neck, after which the bottle is whirled a second time and the column of fat read off on the graduated scale. The reading gives the percentage of fat without calculation. A large number of samples may be tested simultaneously. and the method has been shown to be very accurate after a little practice. It shows only the fat content, which is the com moo measure of richness; but from it and the lactometer reading the total solids and other constituents can be calculated. A bacteriological examination is rarely made in connection with the ordinary milk inspection.
NItti: As Fool). .Milk is peculiarly adapted to be a food for man principally because it contains the four classes of nutrients—protein, fat, car bohydrates, and mineral matter—in more nearly the primer proportions to serve as a complete food than perhaps any other single food material. (See Foon.) A quart of milk contains about four ounces of nutritive material, or about the same as three-quarters of a pound of beef or six ounces of bread. Although these quantities of milk, beef, and bread supply like amounts of total nutrients, their nutritive values arc not the same. In other words, they would not be equally useful as food, owing to the relative proportion in which the nutrients are present. Protein, fat. and car bohydrates occur in milk in about equal propor tions. The ehief nutrients in bread are carbo hydrates and protein. and in meat protein and fat. Either milk o• bread eaten alone would make a better balanced food for 1113n than meat. In general, milk and cream together furnish to the diet of average American families about 20 per cent. of the total food, II per cent. of the total protein, and also of the total fat, and about 5 per cent. of the total carbohydrates. Dairy products (milk. cheese, butter. and cream) furnish over 22 per cent. of the total fond, 12 per cent. of the protein. :32 per cent. of the fat, and 5 per eent. of the earbohydrates.