MILK. 502 MILK. Dion mi-asure of riclincss; but from it and the laetoiiic'tcr reading the total solids and other const itui-nts can bt; calculated. A bacteriological examination is rarely made in connection with the ordinary milk inspection. Milk as Food. Milk is peculiarly adajiled 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 proper proportions to serve as a comjiletc food than perhaps any other single food material. (See Foot).) A quart of milk contains about four ounces of nutritive material, or about tlic same as lliree-(iuarters 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 are 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 chief nutrients in bread are carbo- hydrates and protein, and in meat |irolein and fat. Either milk or bread eaten alone would make a better balanced food for man than meat. In general, milk and cream together furnish to the diet of average American families about 20 per cent, of the total food, 11 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. an<l cream) furnish over 22 per cent, of the total food, 12 ]jer cent, of the protein. :i2 per cent, of the fat, and .5 per cent, of the carbohydrates. As regards the digestibility of all its ingredi- ents, milk is one of the most digestible of animal foods. It has been found that on an average an adult digests about i)7 per cent, of the pro- tein. 05 per cent, of the fat. and 98 per cent, of the carbohydrates of milk. According to American experiments, a child one year old eating milk digests on an average only about ilO per cent, of the protein. 96 per cent, of the fat, and 80 per cent, of the carboliydrates of cows' milk. When milk is taken into the stomach it is speedily curdled by the action of the pepsin and acid of the gastric juice. When eaten alone or in large quantities, the casein gathers in large lumps, which in some persons nuiy be ditricult to digest. This is particularly the case with in- fants and with adults whose digestion is weak. The casein of human milk is precipitated in more llocculcnt form than that of cows' milk, and is thus more easily digested and does not cause irritation. Lime, which tends to prevent the i-urdling of the casein of cows' milk in lumps, is frequently added as lime water to milk that is to be fed to infants or to adults of delicate diges- tion. The results of experiments uj)on the efTect of cooking milk arc conflicting. The more com- mon experience seems to indicate that cooking or heating the milk renders it more diflicult to digest. Sonic persons, however, cannot take fresh milk with comfort, but can digest boiled milk. .Milk is often said to !«> a 'perfect food.' It is so for the yoimg of the species of animal producing it, but there are three reasons why it cannot tie considered n perfect food for adults. ( 1 ) The proportion of water is so large that great quantities (from -I to ."j quarts) would have to he consumed each day in order to obtain the necessary nutrients. (2) The protein is present in rather large quantities as compared with the fats and carbohydrates. Thus the milk necessary to furnish the 0.2S pound of protein per day, estimated to be re(|uired by a man at moderately active work, would yield only 2700 calories of energy, while milk in suflicient quantity to fur- nish the 3400 calories estimated as necessary would yield 0.34 pound of protein. (3) It is a well recognized fact that the digestive functions require that food itself, besides the water taken with it, shall have a certain bvilk. Cattle cannot generally l)e maintained in health upon a con- densed ration such as grain; they seem to require a certain distention of the stomach, such as is brought al)OUt by the fibre (celhilose or woody matter) of grass or hay. In like manner it seems desiralile that man should have a certain amount of bulky material to produce distention or to pro- mote jieristaltic action of the intestines, or for other purposes not well understood. Of course, the nutritive constituents of milk, considered separately, are highly cemcentrated foods. While, therefore, milk alone caimot be considered as a perfect diet for adults, it is of special value as a food for invalids, because it is. as a rule, easily taken, easily digested, and does not generally ir- ritate the alimentary canal. Furthermore, a milk diet is more readily under the control of the ))hysician both as regards quantity and quality than a mixed diet is. If for any reason a child cannot be nourished on mother's milk, the most useful substitute is modified cows' milk. 'arious infant foods and milk substitutes have been proposed and are sold under divers trade names. As a food for adults cows' milk is unusually well adapted for use in connection with other foods, either in its uncooked form in tea and eollee, as a beverage, as bread and milk, etc., or incorporated and cooked with other materials. In many ctilinary (iroducts it can Ite used instead of water, . alysis of bread, rolls, etc.. made with milk would show about one-tenth more pro- tein and one-twentieth more fuel value than bread made with water. Milk is very generally used in many kinds of cake and i)astry and in custards. Where desirable from economical rea- sons, or as a means of increasing the ))ro])ortional amount of protein in a diet, skim milk can be advantageously substituted for whole milk. At the i)rice ordinarily jiaiil in our large cities milk is a food of reasonable cheapness, and at the prices ])revailing in small cities and country towns it is an economical food. Condensed milk is a more nutritious food, pound for ])ound, than fresh milk, since it has lieen concentrated by evaporation. It is, however, usually diluted be- fore it is used, aiul then approximates fresh milk more or less closely in composition and food valtic. If the condensed milk contains added sugar its carbohydrate content is, of course, high- er than that of unsweetened condensed milk, and when diluted, proportionally higher than that of fresh milk. Cream, which contains the greater part of the fat of the milk, as well as some pro- tein and carbohydrates, is chiefly valuable in the iliet as a source of energy. Curds obtained in the manufacture of cheese are eaten to a limited extent. They consist quite largely of the casein of milk, and hence supply the body with building material as well as energy'. Butter and cheese (qq.v. ), the principal milk products used as food, are of great importance as articles of diet.
