Outlines of Dairy Bacteriology, 8th edition / A Concise Manual for the Use of Students in Dairying

if these sources of infection are thoroughly recognized they can in large measure be prevented, and so the troubles which they engender overcome.

is well adapted to nourish bacterial life. Not only does it contain all the necessary nutritive substances bu

ed upon by proteid-dissolving enzyms like trypsin which may be secreted by bacteria. The fat is relatively resistant to change, although a few fo

lthy cow germ life is not found. Only when the gland is diseased are bacteria found in any abundance. In the passage of the milk from the secreting

of milk showing relative size

e of bacterial changes involved. This of course does not exclude the possibility of contamination in the factory, but usually milk is so thoroughly seeded by the time it reaches the factory that the infection which occurs here plays a relatively minor r?le to that which happens earlier. The great majority of the organisms in milk ar

ral sources, which may be grouped under the following heads: unclean dairy utensils, fore milk, coat of animal, and gen

idered, although such material is often present in cracks and angles of pails and cans. Unless cleansed with especial care, these are apt to be filled with foul and decomposing material that suffices to seed thoroughly the milk. Tin utensils are best. W

becomes broken and the can is rusty, the quality of the milk is often profoundly affected. Olson[1] of the Wisconsin

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l cleaned. Where water is run through the machine to rinse out the milk particles, gross bacterial contamination occurs and the use of the machine much i

g of the vats and tanks. Too frequently the cans are not cleaned immediately upon arrival at the farm, so that the conditions are favorable for rapid fermentation. Many of the taints that bother factories are directly traceable to such a cause. A few dirty patrons will thus seriously infect the whole supply. The responsibility for this de

mentations or even contagious di

used for the fresh milk, the probabilities are strongly in favor of some of the cans being contaminated and thus infecting the milk supply of the patrons. If the organism is endowed with spores so that it can withstand unfavorable conditions, this taint may be spread from patron to patron simply through the infection of the vessels that are used in the transportation of the by-products. Co

followed in the Swiss cheese factories, here in this country, as in Switzerland, is fully as reprehensible as any dairy custom could well be. In Fig. 7 the arrangement in vogue for the disposal of the whey is shown. The hot whey is run out through the trough from the factory into the large trough that is placed over the row of barrels, as seen in the foreground. Each patron thus has allotted to him in his individual barrel his portion of the whey, which he is supposed to remove day by day. No attempt is made to clean out these receptacles, and the inevitable result is

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is handled. Each patron's share is placed in a barrel, from which i

f solution. One is to use another separate set of receptacles to carry back these products to the farm. This method has been tried, and while it is deem

sed for this purpose to

necessary. In most factories steam, generally exhaust, is used directly in the milk, and experience has shown that such milk, without any cooling, will keep sweet for a considerable number of hours longer than the untreated product. It is noteworthy that the most advanced and progressive factories are the ones that

e most fundamental and important problems in dairying. All such apparatus should be so constructed as to permit of easy cleaning.

the milk. Then wash thoroughly in hot water, using a good washing powder. The best washing powders possess considerable disinfecting action.[5] Strong alkalies should not be used. After washing rinse thoroughly in clean hot water. If steam is available, as it always is in c

hat come in contact with the milk must be kept equally clean. Cloth strainers, unless attended to, are objectionable, for the fine mesh

niences which are generally to be found on the farm has led in some cas

ng will be subject to great fluctuations; but, nevertheless, such determinations are of value as giving a scientific foundation for practical

y steaming. Before milking, the udder was thoroughly cleaned and special precautions taken to avoid rais

er cc. Hours b

pail 1

y pail

water and numerical determinations of this rinsing water made. In poorly cleaned cans, the average germ content was 442,000; in cans wa

a sterile swab to remove dirt. Then repeat the process twice or more with fresh rinsing waters,

a in differ

. Total No

450,000 49,0

3,400 35,

05,000 61,4

ore milk, i. e., the first few streams from each teat, and that which is subsequently withdrawn, generally reveals a very much larger number of organisms in the fore milk.[7] Not infrequently will this part of the milk when drawn under as careful conditions as p

t at different p

2000th cc. 4300th cc.

500 1,700

00 1,650 40

hat too small quantities of milk were used in the examinations and so erroneous conclusions were drawn. This marked diminution in numbers indicates that the larger proportion of the organisms found in t

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ior with the milk cistern. Milk sinuses are mostly shown in cross se

e or less tightly closed by the circular sphincter muscles, thus preventing the milk from flowing out. The mucous membranes of the milk duct and cistern are naturally moist. The habits of the animal render it impossible to prevent infection of the external opening at the end of the teat and there is no mechanical reason why bacteria cannot readily find their way along the moist lining membrane for som

he region of the milk-secreting tissue than in the lower portion. Ward's conclusions are "that milk when secreted by the glands of a healthy udde

occasional intervals. Moore[9] in the examination of 9 udders found 20 different forms, and of these only 3 species predominated, all of which proved to be micrococci. S

rms allied to the colon bacillus. Such findings are, however, due in all probability to accidental in

ion answers the origin of the cocci that are so generally found in the upper portion of the udder is questionable. The statement is ordinarily made that the inner tissues of healthy organs are bacteria-free, but the studies of Ford[15] seem to indicate that 70 per cent. of such organs, removed under aseptic conditions from guinea pigs, rabbits, dogs and cats contained living organisms. Others have reported similar result

ophytic forms, such as B. prodigiosus, lactic acid bacilli and others. In no case has it appeared evident that actual growth has occurred, although the introduced organism has been demonstrated in diminishing numbers for 5-6 days. Even the common lactic acid germ and a yellow liquefyi

ed by Fokker[19] that this same property was found in freshly drawn milk. This peculiarity h

Nothing is known as to the cause of this apparent germicidal action. The question is yet by no means satisfactorily settled, although the facts on which the hypothesis is based are not in controversy. If such a peculiarity belongs to milk, it is not a

is worth while, except in the case of "sanitary" dairies where milk is produced with as low a germ content as possible. The intrinsi

isms are derived from the surrounding air and the utensils in which the milk is received and stored. The number of organisms which find their way into the milk depends largely upon the ch

rectly traceable to the animal herself and the condition of the milk utensils. Fortunately both of the

lation. Such a view has no foundation in fact as bacteria absorbed into the circulation are practically all destroyed in the tissues by the action of the body fluids and cells.[23] While organisms cannot pass readily from the intestine to the

the fecal matter is in part dependent upon the character of the food. The more nitrogenous rations with which animals are now fed leads to the production of softer fecal

l attention is paid to the removal of the manure. All dairy stalls should be provided

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gelatin surface. The adherent bacteria developed readily in this medium, and the number of bacteria t

placed with every movement of the animal. Every hair or dirt particle so dislodged and finding its way into the milk-pail adds its quota of organisms to the liquid. This can be readily demonstrated by placing cow's hairs collected with care on the moist surface of gelatin culture plates. Almost invariably, bacteria will be found in considerable numbers ad

his undissolved residue bespeaks filthy conditions as to milking. From actual tests made, it is computed that the city of Berlin, Germany consumes about 300 pounds of such dirt and filth daily. Renk has laid

he species is of even greater import. Derived primarily from dirt and fecal matter, it

g is to be condemned. The milker's hands should be washed immediately before milking in clean water and dried. A pinch of vaseline on hands is sometimes used to obtain a firmer grasp and prevents the ready dislodgment of scales.[25] It must also be borne in mind that the milker may spread disease through the milk. In typho

ne but found a much higher germ content than with hand-drawn milk. The recent introduction of the Burrel-Lawrence-Kennedy machine has led to numerous tests in which very satisfactory results have bee

y grooming lessens very much the grosser portion of such contamination, but with a dry, hairy coat, fine scales and dust particles must of necessity be dislodged.[28] Ordinarily the patron thinks all evidence of such dirt is removed if the milk is strained, but this process only lessens t

contributes to instead of diminishing the germ life in milk. The strainer cloths unless washed and thoroughly sterilized by boiling harbor multitudes of organisms from day to day and may thus actually add to the organisms present

below upward. The filtering substance is washed in hot water immediately after use and then steamed and finally baked. While it is possible to remove the solid impurities in this way, the germ content cannot be gr

dirt, hairs, epithelial scales and cells, also some of the casein, making what is known as centrifuge slime. This conglomerate mass is incomparably rich in germ life and the natural inference would be that the bacterial content of the milk would be greatly reduced by this procedur

tion of much organic matter and bacteria, such clarifi

uch milk. This practical disadvantage together with the increased expense of the operation and the failure to materially enhance the keeping quality of

coat of the animal thus subserving the double purpose of cleaning the animal and preventing in large measure the continual dislodgment of dust particles. After these parts have been well carded to remove loose hairs and dirt particles, the skin should be thoroughly mo

er[35] who found that the actual amount of dirt dislodged from udders of apparently clean animals during the milking process was three and one-half times as much as when the cow's udders were washed

animals it was reduced to 192. From numerous tests made in the writer's laboratory, it is evident that the germ content of the milk in the pail is increased from

s have been devised for this purpose. In one case the pail is smaller at the top than bottom, but in most of them the common form is kept and the exposed area is lessened by means of a cover, the milk being received through a narro

ed to diminish the introduction of

ed from passing into the milk. Eckles examined one in which the germ content was found to be 3200 per cc. as against 43200 per cc. i

life floating in the air. Dust may vary much in its germ content depending upon its origin. Fraser found the dust from corn meal to contain only about one-sixth to one-eighth as much germ life as that from hay or bran.[36] In time most of these dust particles settle to the floor, but where the herd is kept in the barn, the constant movement of the animals keeps these particles more or less in motion. Much can be done by forethought to lessen the germ content of stables. Feeding dry feed should not be done until

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developed from the bacteria which fell in 30 seconds on the surface of the gelat

y into milk. Where the manner of milking and handling is designed to exclude the largest number of organisms possible, the bacteria appearing in the fore milk make up the major portion remaining. By putting into practice the various suggestions that have been made with reference to diminishing the bacterial content of milk, it is possible to greatly reduce the number of organisms found therein, and at

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olony growing on gelatin plate. Compare with Fig. 13, where same quantity o

milk that was used in making the culture indicated by Fig. 13. The first plate was inoculated with milk drawn under good conditions, the germ content of which was f

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content is shown by smaller number of colonies (330 bacteri

recommendation of the board of examining physicians. Thus, the Pediatric Society of Philadelphia requires all children's milk that receives its recommendation to have not more than 10,000 bacteria per cc. Such a standard has its value in the scrupulous cleanliness that must prevail in order to secure these results. This in itself is practically a guarantee of the absence of those bacteria liable to produce trouble in children. The number of organisms found in such milks is surprisingly low when compared with ordinary milk. Naturally, there is considerable fluctuatio

n in 1900, milk and cream from several such dairies in the United States were shipped to Paris, arriving in good condition after 15 to 18 days transit. When milk has been handled in su

epends largely upon the way in which the product is used. To the milk-man engaged in the distribution of milk for direct consumption, all bacterial life is more or less of a detriment, while to the butter-maker and cheese-maker some forms are a direct necessity. It is unnecessary and impracticable to require the same degree of care in handling milk destined to be worked up into f

words of the eminent German dairy scientist, Prof. Fleischmann, when he says that "all the results of scientific investigation which have found such grea

ter of fact, growth does not begin at once, even though the milk may be richly seeded. At ordinary temperatures, such as 70° F., no appreciable increase is to be noted for a period of 6-9 hours;

ent is attributed to the germicidal

More or less development of all types go on, but soon the lactic species gain the ascendency, owing to their being better suited to this environment; they soon outstrip all other species, with the result that normal curdling generally supervenes. The g

ct on the rate of development. When milk is not artificially cooled, it retains its heat for some hours, and consequently the conditions be

c. in milk kept at di

F. 9

r milking 1

25,000 1

46,000

5,700,000

cooling milk on the

han the original infection of the milk itself. Milk which curdled in 18 hours at 98° F., did not cur

preciable amounts. Running well water can be used for cooling, if it is possible to secure it at a temperature of 48°-50° F. The use of ice, of course, gives better results, and in summer is

he cooled night milk to the warm morning milk sometimes produces more rapid changes in both. The explanation for this often imperfectly understood phenomenon is that germ growth may have gone on in the cooled milk, and when this mat

n be older. This is due largely to the more wide-spread use of ice for chilling the milk en route to market. Examinations have been made of various supplies with the following results: Sedgwick and Batchelder found in 57 tests of Boston milk from 30,000-4,220,000 per cc. Jordan and Heineman found 30% of samples of Chicago milk to range from 100,000 to 1,000,000 while nearly one half were from 1-20,000,000 per cc. The g

h a standard difficult. Some hold, as Park, that such a standard is feasible. The New York City Milk commission has set a standard of 30,000 bacteria per cc. for their certified milk and 100,000 per cc. for inspected milk. Rochester, N. Y. has attempted the enforcement of such a standard (limit, 100,000 per cc.) with good results it is

relationship between the development of acidity and the growth of bacteria, yet in a general way one follows the other at normal temperatures. Where the temperature is kept rather low, bacterial growth might go on without much acid development, but in the great majority

the proper quantity of the solution necessary to neutralize say, 0.2 per cent. lactic acid. Then, as the milk is delivered, the proper quantity is taken from each can to which is added the tablet solution. A retention of the pink color shows that there is not sufficient acid in the milk to neutralize the alkali used; a disappearance of color indicates an exces

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te tea cup. To this is added the quantity of milk by means of the cartridge measure which would just be neutralized if

and foreign matter the milk contains, the larger the number of varieties found in the same. While milk may contain forms that are injurious to man, still the great majority of

e producing no visib

king up the milk sugar with or

apable of rendering the casein of milk sol

ct the chemical characteristics of the milk somewhat, but not to the extent that it becomes physically percepti

ese organisms are the distinctively milk bacteria, although they do not predominate when the milk is first drawn. Their adaptation to this medium is normally shown, however, by this extremely rapid growth, in which they so

f resistance due to spores makes it difficult to eradicate this type, although they are materially held in subjection by the lactic bacteria. The number of different kinds that have been found in milk is quite co

lk, and transforming these in such a way as to produce by-products that impair the flavor or appearance of the liquid; or it may be produced by

ich milk possesses of being able to absorb volatile odors, the fat in particular, having a great affinity for many of these subs

odor and taste; sometimes this is apt to be bitter, at other times salty to the taste. It is a defect th

strong-flavored substances as garlic, leeks, turnips and cabbage. The volatile substances that give to these vegetables their characteristic odor are quickly diffused through the system, and if such foods are consumed some few

eless for human use. Troubles from such sources could be entirely obviated by feeding limited quantities of such material immediately after milking. Under such conditions the taint produced is usually eliminated before the next milking.

stor oil, sulfur, turpentine, jalap, croton oil, and many others have been used as medicine. Such mineral poisons as arse

fter being drawn from the animal, it will absorb them readily, as in the barn, where

nder either condition, it absorbs volatile substances with considerable avidity. In this test fresh milk was exposed to an atmosphere impregnated with odors of various essential oils and other odor-bearing substances. Under these conditions, the cooler milk was tainted very much less than the milk at body temper

inconsistent with proper dairy practice, and in the light of the above

rb odors as seen where the same is stored in a re

sh milk, it is relatively easy to distinguish between taints caused

dicines. If, however, the intensity of the taint grows more pronounced as the milk becomes older, then it is probably due

ed is preferable) by inoculating same with some of the original milk. Not all abnormal fermentations are able though to compete

is often possible to materially improve its condition. Thorough aeration has been frequently recommended, but most satisfactory results have been obtained where a combined process of aeration and pasteurization was resorted to. Where the

een given already under the respective sources of infectio

and Storch in Denmark have both experimented on the influence of aeration in butter making, but with negative results. Marshall and Doane failed to observe any material improvement in keeping quality, but it is true that odors are elimina

ll some distance so that it is brought intimately in contact with the air. This latter process is certainly much more effective if carried out under conditions which preclude in

rely solved when the milk is delivered to the factory or creamery, although it might

leaning pumps and pipes. The difficulty of keeping these utensils clean often leads to neglect and subsequent infection. In Swiss cheese factories, the custom of using home-made rennet solutions is responsible for considerable factory infection. Natural rennets are

e reason that the floors and wall are, as a rule, quite damp, and hence germ life cannot easily be dislodged. The majority of organisms found under such conditions come from the person of the operators and attendants. Any infection can easily be prevented by having the ripe

ut and especially under the factory. The emanations from these give the peculiar "factory odor" that indicates fermenting matter. Not only are these odors absorbed directly, but germ

such numbers that the normal course of fermentation may be changed. The quality of the water, aside from flavor, can be best determined by making a curd test (p. 76) which is done by adding some of the water to boiled milk and incubating the same. I

urized milk succeeded in producing the undesirable flavor. The danger from ice is much less, for the reason that good dairy practice does not sanction using ice directly in contact with milk or cream. Then, too, i

TNO

Rept. Wis. Exp

Bull. 131, Kan. Exp

h has the property of decomposing hydrogen peroxid. If milk is heated to 176° F. (80° C.) or above, this enzym is destroyed so that the above reaction no longer takes place. If potassium iodid and starch are adde

Y. Prod. Rev.,

79, Md. Expt. S

ept. Ont. Agr'l Co

l Expt. Stat., Jan. 1899; Ward, Bull.

1896, p. 108; Moore, 12 Rept. Bur. Anima

ia in Milk, N. Y.

Cent. f. Bakt., II

Rept. Ont. Agr. Co

ll. 147, Mich. Ex

Bull. 158, Cornell Ex

Stat., p. 277. Bolley (Cent. f. Bakt., II Abt., 1: 795, 1895), in 30 experiments found 12 out of 16 species to be

urn. of Hyg.,

enreich, l

l. 42, Storrs Expt

205, 1898. Appel, Milch Zeit., No. 17, 1900. Harrison and Cumming, Journ. Ap

Zeit. f. Hyg.

h, Ann. de Micro

. 197, Cornell Expt

Cent. f. Bakt., II

hough Ford (Journ. of Hyg., 1: 277, 1901) claims to hav

Milch Zeit.,

ich, Die Bakte

l. 42, Storrs Expt

nt. f. Bakt., II

h. and Agr. Soc. Scotland

in the Copenhagen filters while in the more extended work of Dunbar and Kister (Milch Zeit., p

onheim, Journ. f. La

es, Bull. 159 Iowa E

, p. 753, 1899. Harrison and Streit

l. 88 Md. Expt.

oard's Dairyma

Bull. 91, Ill

. 91, Ill. Expt.

l. 42, Storrs Expt

Landw. Inst. Univ. K

tz, Nat. Med. Re

Soc. Amer. Bact

h, Ann. de Micro

ll. 26, Storr

supplied with milk tha

Y. Univ. Bull.

. 59, Iowa Expt.

. 59, Iowa Expt.

Rept. Wis. Expt.

o. 9, U. S. Dept. Ag

mmissioner of Agr., Canad

Hoard's Dairyma