CHAPTER II. THE HYGIENE OF HABITATIONS. (Part 10)

extracted from skim milk is also used for various purposes in the commer- cial manufacture of sizing for paper, etc. Standards. — The relative composition of milk and some of its products given above are only the aver- age composition, found after an examination of a great number of samples of milk, etc., with large variations in the relative composition. In order, however, to guard the welfare of the public and pre- vent substitution, adulteration, and selling inferior grades of products, municipalities. States, and the federal government have instituted certain minima of compositions or standards below which milk and its products must not go and must not be sold to the public. Solids. Per cent. Fat. Per cent. Solids not fat. Per cent. Water. Per cent Milk . . . 11.75 3.25 8.5 88.25 Skim milk 9.25 Condensed milk 28 . 00 7.00 72.00 Cream . 18.00 Butter . . . 82.50 Cheese 50.00 The New^ York State standard for milk was 12 per cent, solids and 88 per cent, water until 1910, when it was lowered by act of Legislature to 11.5 per cent, solids and 88.5 per cent, water. The New York City standard for milk is 12 per cent, solids, of which 3 per cent, must be milk-fat. MILK ruonrcrs 127 Other States and eilie> lia\f slight xariatioiis from these standards. "Standards are hased n|)nn data representing: niate- rial> pnxhiced nnder American conditions and are fixed as such that a dej)arture from above or below the minimum h'mit tlie' preserilx' is evideuee that such articles are ot" inferior (piaHt \ . 'I'he hmits fixed as standanis ai'e not necessarii- the extremes authen- tieally recorded for the articles in f|nestion, such extremes being (hie to al)normal conditions as a rule." iWili'v.) Official Definitions. — The followinjj; are the ofhcial definitions of milk and its products according to the liiited States Department of Agriculture: Milk. Milk is the fresh, clean lacteal secretion ol)taiiied by the complete milking of one or more healthy cows, proj)erly fed and kept, excluding that obtained within fifteen days before and ten days after eahing. Blended Milk. JJlended milk is milk modified in it> comi)osition so as to have a definite and stated percentage of one or more of its constituents. Skim Milk. Skim milk is milk from which a part or all the cream has been rem(»'ed. Coiulenscd or Kvaporatrd Mill:. ( 'ondensed or evaj)orate<l milk is milk from which a con>idcrable l)ortion of water has been e\aporated. Hiiftrnnill:. liuttermilk is the product which re- main> when butter i> rcmo\cd from milk or cream in the ])rocess of churning. Crrani. ("ream is that |)ortion of milk, rich in milk- fat, which ri^es to the >urface of milk on standing, or is separated from it by centrifugal force. 128 HYGIENE OF FOODS AND FOOD SUPPLY Buffer. — Butter is the clean, non-rancid product made by gathering in any manner the fat from fresh or ripened milk or cream into a mass, which also contains a small portion of the other milk constituents, with or without salt. Cheese. — Cheese is the sound, solid, and ripened product made from milk or cream by coagulating the casein thereof with rennet or lactic acid with or with- out the addition of ripening ferments and seasoning. Whey. — Whey is the product remaining after the removal of fat and casein from the milk in the process of cheese-making. Koumiss. — Koumiss is the product made by the alcoholic fermentation of cows' or mares' milk. Kefir. — Kefir is a product made by a specific yeast fermentation of milk. MILK ADULTERATION. Milk is adulterated in several ways: (1) By addi- tion of water; (2) by subtraction of cream; (3) by both addition of water and subtraction of cream; (4) by addition of coloring matter, thickeners, and certain harmless substances; (5) by addition of skim milk; (6) by addition of chemicals as preservatives. Addition of Water. — This is one of the most prevalent methods for the adulteration of milk. It is so easy, apparently difficult of detection, and changes the ap- pearance and general physical quality of the milk so little that it is often resorted to by dishonest dealers and producers. The addition of water to milk reduces its quality by diluting it, and the whole mass is less MILK ADri.TERATlOS 129 nutritions and has t'cwt-i' fond in^'ri'dionts than normal milk. 'I'his !>> a liiirmt'nl adnltcration hrt-ansi' it reduces the (|nalit,\ of the milk, and when fed to children proves injurious to their health. It is al>o a fraudulent adulteration hecau.se it substitutes an inferior product for the same price that the superior would .sell for. Extraction of Cream.- 'I'he extraction of cream, or what is called "skinuninj;," is also a frecpient mode of milk adulteration. It is perhajjs even more in vogue amont: dealers than sim|)le watering;, becau.se it is so much mi>rc profitaMe and difficult to detect. A forty-(|uart can of milk which sells for Sl.tiO will })ring the dealer hut 1() to 20 cents of additional i)rofit when he adds four or five quarts of water to the can. If, however, the dealer removes two quarts of cream of the six or seven which the can contains he gains the price of the two quarts of cream (40 to 60 cents) less the price of the two extracted quarts, which amount to only S cents. This shows that the skimming of milk is a very profitable procedure, even when it is hut partial. Indeed, a great deal of the milk in cans, which is >old at the markets and by grocers for a low price. i-« more or Ie^>. >kim milk. Skimming and Watering. - Skhnming of milk makes it heavier by subtraction of the fatty or lighter portion, thus increasing its specific gravity and density. A skim milk will read from 32 to .3S on th<' Qnevenne lactometer and from 1 10 to IIS on the Board of Health lactometer, according to the amount of cream taken oft". In order to disguise this higher specific gravity and to reduce it, dealers who make their own tests add sufficient water to reduce the density of the 9 130 HYGIENE OF FOODS AND FOOD SUPPLY skim milk, so as to make the readings on the lac- tometer about the normal, and thus try to deceive the inspector who relies too much on the lactometer examination alone. Skimming, as well as skimming and watering, reduces the nutritive quality of the milk and is a harmful as well as a fraudulent adulteration. Addition of Skim Milk. — The addition of skim milk to normal milk reduces the quality of the whole milk and is harmful as well as fraudulent. One of the principal reasons for the prohibition of the sale of skim milk in some cities is the tendency of dealers either to sell skmi milk for whole milk, or to reduce whole milk by the addition of the skimmed. Addition of Coloring Matter and Other Harmless Ingredients. — The addition of coloring matter is mostly practised to disguise the poor appearance of skim or watered milk and make it look richer. The coloring matter most commonly used is a vegetable coloring "annatto." The other colors used belong to the coal-tar family (azo-colors) and are harmful in comparison to coloring with "annatto," which is harmless. Their detection is possible only by chemical tests. Sodium bicarbonate is sometimes added to milk which is beginning to turn sour, in order to disguise the acid taste. In small quantities the addition of soda is harmless, but the procedure is dishonest in that its purpose is to palm off milk which is acid for fresh milk. Thickeners are ^Try seldom put into milk, more frequently into cream and condensed milk. Addition of Chemicals. — See p. 140. Ml l.l\ /7.7;.s7-7.'r.r/7N.V MILK PRESERVATION. Milk Deterioration. The milk scd'ction of noniial cows ^t'lll;liM-^ In ;i iior'iiKil state lor a coiiiparat i\ cjy short |)ci'io(j, ami iiii[>oi-taiit cliaiii^c^ occur wry soon. it' left iiii(li>tnrl)e(| at the iioi-iiial lioiix- tempera- ture fresh milk shows >ome physical cjiaii.^^es within si.x to twelxc liours, and hy tJiis time it has also passed tliroiif^h eortaiii eliemieohiolo^ieal changes. Tlie pliysical clianges are limited to the separation of the fat ulohules and the .sej)aration of the cream layer at the npj)cr portion of the vessel containinji; the milk. Tliei-e is also a reduction of the tonij)erature of the milk fi-om that at which it was ^•oi(jed to the tem- peratin-e of tlie room. The other ehan<;es which occur are a souring which is slight at first and later increases. If milk is left at the same tenii)eratnre for longer periods a distinct coagnlatioii or cnrdling dc-e|o])s, owing to the hardening and separation of the casein. .\t the same time there is some gas formation and a liitter taste in the milk may heconie noticealtle. .\ll these changes are included in the term "deterioration"" of milk. These j)henomena arc only the outward and noticeahle changes; the real physical, chemical, and biological cliant,'-cs arc, of course, more complex, and camiot he so easily detected. To what arc these changes in the milk due? Causes of Deterioration. The separation of the cream is easily acconnteil for l»y the coni|iarat i\ c lightness of the fat glohulcs which coalesce and rise to the top. The other noted <lianges are i[U' to the micro- 132 HYGIENE OF FOODS AND FOOD SUPPLY organisms. A perfectly sterile milk, that is, one abso- lutely free from bacteria, has never been obtained. Microorganisms are found in the ducts of the teats and udder of the cow, and even milk obtained by cannula already contain a certain number of germs. Immediately after secretion the milk begins to be contaminated with numerous germs from the air in the stable, the hands of milkers, the udder and teats of the cow, the surfaces of strainers, pails, etc., so that by the time the milk is taken out of the stable it contains a very large number of bacteria. The number of bacteria usually remains stationary for a few hours owing to the so-called " germicidaV' power which the milk possesses at this initial stage of its existence outside the cow. Sooner or later, according to the condition of temperature, the bacteria begin to develop and multiply, so that after a certain time they are so numerous as to be counted by the million in the cubic centimeter. The number of the bacteria is not the most impor- tant factor, but their importance lies in the kinds of the multiplying germs. These bacteria which get into and develop in milk are of several kinds. In the first place there is the group of germs named "lactic acid" bacteria. By acting upon the lactose they convert it into lactic acid and thus favor the gradual souring which on reaching a certain stage causes coagulation of the casein with consequent curdling of the milk. Another group is composed of the "gas-forming" or "aerogenous" bacteria which are said to cause the gas formation in deteriorated milk. The butyric- and proteid-decomposing bacteria may L Mii.K i'ifi:si':R.\r/(>\ 133 also (U'voloj) siiiiult;iiic(m>ly with the hictic iicid germs. There arc imiiicrdiis ntlier jierins wliicli may at the same time act u)uu tlic milk. The lactic acid hacteria are important hecaiise they cause the souring of the milk and its sul)se(jucnt cunllini:. As far as health and food value are concerned, lactic acid for- mation is not necessarily a harmful process. The ingestion of even very large (juantities may not be harmful to health; indeed, in many cases it is even beneficial. Buttermilk and whey contain enormous quantities of the lactic acid germs, but are drunk with profit to health. They also possess another beneficial action in that they counteract other more harmful bacteria. While lactic acid fermentation is active and at its height, it is germicidal to other bacteria, which camiot develop in an acid mediiun. In may there- fore be said with truth that the lactic acid fermenta- tion process is not per se a harmful ])rocess. The gas-producing, tlie l)ut\ ric- and i)rotein-decom- posing germs are of more importance to health, because they are of harmful character. They produce putre- faction and decomposition, they develop a bitter taste ami foul odors, and may also j)roduce certain toxins, which max- become very harmful to those higesting tlic fluid. Conditions Favoring and Retarding Bacterial Growth in Milk.— In view of the rai)idity of the growth and the various characters of bacteria, it is important to nr)te the conditions which favor and retard their growth and development, (ienerally, low tempera- tures, very high temperatures. al)solute dryness, and certain chemicals are unfavorable to the life and irrowth of germ life. 134 HYGIENE OF FOODS AND FOOD SUPPLY Moisture and a temperature })etween G0° and 100° F., on the other hand, are very favorable. Dryness. — ]\Ioisture is necessary for germ hfe, and bacteria develop very slowly, if at all, in a dry medium. It is, of course, difficult to obtain absolute dryness, which alone is inimical to bacterial life, but if milk is dried and kept in the form of a powtler it may be preserved for some time, although this applies more to milk-powder from skim milk than to powdered whole milk, as the cream is said to become rancid if in powder form. Low Temperature. — By low temperature is meant any temperature between 50° F. and the freezing-point. A low temperature does not destroy, but stops growth and development of bacteria. Their number remains the same, but they are in stunned form, always cap- able of doing mischief, even under these conditions. Thus it is known that typhoid fever bacilli may be alive for long periods even in ice or frozen milk, and such milk may therefore produce the disease. While bacteria do not grow in frozen milk, they do grow in milk kept at temperatures between 34° and 50° F., but only very slowly. The varieties which grow at these low temperatures are not the lactic acid bacteria, but those wdiich are likely to do harm if the milk is kept too long at these temperatures. Milk kept at temperatures between 34° and 50° F. may be preserved for several days to a week and more, the lower the temperature the longer. The milk will not become sour, but it may become unfit for use because of the development of the other bacteria and their products. ^f 1 1. K i'h'i:si:h' .\ tion i :i") Miiiii I' iiijirrdtnif. Tlir «'ir('ct upon milk kvpt at tt'iiiiMTaturcs lu'twccM .")(l° and 100° I-\ xarics acford- ini; To the (Iri^rcc of tcnipcrat urt' ami (IcjH'ndN upon tlic kind of hartt-ria which tiio trrnjx'ratnrcs I'axor in growth and dovolopniont and nuiltiplicution. 'ari()us bacteria have a ditt'erent and varying point of thermal deatli. as well as a temperature at which growth and develo|)ment are most abundant. Lactic aciil bacteria, for instance, develop most rapidly at a temjHTatnre of i&#123;)° to 70° F., at which they multiply more tjuickly than any other species. As their devel- opment is inimical to the growth of other germs, milk kept at ()0° to 70° F. will sour and contain lactic acid l)acteria to the exclusion of almost all others. At the higher temperatures between S0° and 100° F., the lactic acid bacteria clo not always gain a pre- dominance, but often others, especially the gas-pro- ducing bacteria, gain the upper hand and then in addition to the acid bacteria the milk contains other less desirable germs. High Temperatures. — High temperatures, /. e., tem- peratures above 100° V., are inimical and unfavor- able to the life and growth of bacteria, and the various bacteria have their own thermal death-point. Some are destroyed at temperatures of from 120° to 140° F., kept up for a certain period; to destroy others requires, for an hour or more, a tcmj)erature above the boiling- |)<»int of water. l''xcci)t for a few sj)ecies, bacteria cease growing when the temperature is raised above 100° F. and begin to die when it is above 120° to 140° F., according to time of exposure to heat. At higher temperatures the bacteria arc more (|uickl>' destroyed 136 HYGIENE OF FOODS AND FOOD SUPPLY and in less time. Bacteria which bear spores are the most difficult to kill, and sometimes must be subjected to a very high temperature for a long time before they are destroyed. Most of the active germs, including the pathogenic bacteria of most common diseases, like typhoid, diphtheria, and tuberculosis, are killed at temperatures of 140° F. kept up for twenty minutes, and at higher temperatures kept up for less time. Chemicals. — Certain chemicals are inimical to bac- terial life and growth, although the number of these chemicals applicable to milk is, comparatively, very small (see page 141). Milk Preservation by Cold. — As previously indicated, cold, /. e., a temperature of from 32° to 50° F., does not destroy the germs in milk but merely inhibits and stops their growth and multiplication and thereby keeps the milk from becoming sour and decomposed. The length of time for which milk may be preserved by cold depends upon the number and the kind of germs originally in the milk before its temperature was reduced. It may vary from twenty-four hours to a week; frozen milk has been known to keep for longer periods, and is an article of commerce in Siberia and other northern countries. While the souring of the milk is undoubtedly postponed, it is not certain that its decomposition by other bacteria is avoided. Thus milk kept under low temperatures may keep sweet, and yet at the same time develop dangerous qualities. The main advantages of cold as a preserva- tive are that it does not change the appearance and composition of the milk, and is valuable as an aid in preserving clean milk for a moderately short time. It MILK rh'i:si:h'.'no.\ i:i7 must