CHAPTER III. COMPOSITION OF MILK.
The composition of milk, though frequently discussed, is not generally well understood. It is quite variable, not only in the milk from different cows, but in that from the same cow at different times, and in different conditions, but especially at different seasons of the year. It is more buttery in winter, and more cheesy in summer. A cow milked three times a day would give more in quantity but poorer in quality, than if milked twice; while one milked twice a day will yield more milk than if milked once a day, but one milking a day would be the richer. The first milk drawn from the udder is more watery than what follows; the last is the richest. The accumulation of milk in the cow's bag is influenced by the law of gravitation. The water being the heaviest ingredient, settles to the bottom, and is the first milked; the cream, which is the lightest, rises, and is the last milked. That is to say, a partial separation takes place in the udder, sufficient to make the "strippings" some ten or twelve times as rich in butter as the first milk drawn. We would, therefore, infer that the first third contains the most water, the second third the most cheese, and the last third the most butter. There is said to be a difference in the milk drawn from the compartments of the udder of the same cow, or from different teats.
The variation in the composition of milk, of course, is indicated by different chemical analyses, no two of which can be found to exactly agree. We give an analysis by Haidlen. He found that the specimen contained, in 1,000 parts, 873 parts of water, 30 of butter, 48.2 of cheese, 43.9 of sugar of milk, 2.31 of phosphate of lime, .42 of magnesia, .47 of iron, 1.04 of chloride of potassium, and .66 of sodium and soda. Other chemists have found albumen among the constituents of milk, and this ingredient is believed, by many, to be the one that first commences decaying, in hot weather, and produces, "tainted" milk, "floating" curds, and "huffy" cheese. Skimmed milk has been found, in some instances, to contain as high as 97 parts of water in 100, and only 3 per cent. of solids, or cheesy matter. "Swill milk" has been found to contain as low as 1½ per cent. of butter. An analysis of the first milk taken from a cow's bag after calving, showed it to consist of 15.1 per cent. of caseine, or cheese, 2.6 of butter, 2 of mucous matter, and 80.3 of water. Ordinary pure milk will average about 12½ per cent. of cream. But it is not unfrequently found to yield 15 to 20 per cent., and even as high as 25 per cent. of cream has been obtained. If milk yields less than 10 per cent. of cream, it is below the average, and unprofitable for butter-making.
We know of no single instrument that will at once indicate the quality of milk. What is called the lactometer, but is properly a hydrometer, will indicate the density of milk, and if its specific gravity in a pure state be known, it will show the amount of water added, if any. On an average, milk is about 4 per cent. heavier than water. That is, a hydrometer with a scale graded at 100 for milk at 60° Farenheit, ought to sink to 96 in water. The variation in the density of milk will be shown by an experiment given by Charles L. Flint, in his "Milch Cows and Dairy Farming." He says:
"For the purpose of showing the difference in the specific gravity of different specimens of pure milk, taken from the cows in the morning, and allowed to cool down to about 60°, I used an instrument graduated with the pure milk mark at 100, with the following results: The first pint drawn from a native cow stood at 101. The last pint of the same milking, being the strippings of the same cow, stood at 86. The mixture of the two pints stood at about 93½. The milk of a pure bred Jersey stood at 95, that of an Ayrshire at 100, that of a Hereford at 106, that of a Devon at 111, while a thin cream stood at 66. All these specimens of milk were pure, and milked at the same time in the morning, carefully labeled in separate vessels, and set upon the same shelf to cool off; and yet the variations of specific gravity amounted to 25, or, taking the average quality of the native cow's milk at 93½, the variations amounted to 17½."
It will be seen, by these experiments, that the richer the milk in butter, the less the specific gravity, thin cream being 30° below the water mark. The richer the milk in caseine, or cheese, the greater the specific gravity, the milk of the Devon indicating 15° above the water mark. Watering milk will of course reduce the specific gravity of milk rich in cheese, and by this means it can be made to indicate the average density of pure milk. In the same way, milk rich in butter may have its specific gravity increased until it nearly reaches that of water, but no amount of watering can make it indicate over 96°, which is the figure given for pure water. A little salt, or other ingredient, may be added to bring the density up to the pure milk mark. So the blueness of milk, produced by either skimming or watering, may be removed by the use of burnt sugar, which will give it a rich color. Or annotto may be used for the same purpose. Many expedients have been resorted to, from time to time, by the dishonest, for the purpose of disguising the impoverishment of milk by skimming and watering.
"But," says some one, "why tell dishonest men how they can skim and adulterate their milk?" We have not done so. We have told honest men some of the practices of the dishonest, with the view of enabling them to detect the fraud. True, the hydrometer is not an accurate or legal test; but it shows the exact density of the milk tried, and this is a very important point. When you have decided this, by the use of the cream-gauges, you can determine the amount of cream; and if you let the milk stand until it coagulates, and the cheese separates from the whey, you can tell the relative proportion of water and cheese. This may be a somewhat slow and clumsy process, but it is nevertheless decisive, and often repays the trouble. Foreign substances, so far as not held in solution by the water, or not entangled in the cheese or cream, will settle at the bottom of the glasses. Besides, with these evidences to start on, the ways of a suspected person can be watched, and he often be caught in the very act of violating the law, which we quote below:
§ 1. Whoever shall knowingly sell, supply, or bring to be manufactured to any cheese manufactory in this State, any milk diluted with water, or in any way adulterated, or milk from which any cream has been taken, or milk commonly known as skimmed milk; or whoever shall keep back any part of the milk known as "strippings;" or whoever shall knowingly bring or supply milk to any cheese manufactory that is tainted or partly sour from want of proper care in keeping pails, strainers, or any vessel in which said milk is kept, clean and sweet, after being notified of such taint or carelessness; or any cheese manufacturer who shall knowingly use, or direct any of his employes to use, for his or their individual benefit, any cream from the milk brought to said cheese manufacturer, without the consent of all the owners thereof, shall, for each and every offense, forfeit and pay a sum not less than twenty-five dollars, nor more than one hundred dollars, with costs of suit, to be sued for in any court of competent jurisdiction, for the benefit of the person or persons, firm or association or corporation, or their assigns, upon whom such fraud be committed.