THE UNIVERSITY OF ILLINOIS LIBRARY . >O AGRICULTURAL IIBRARV UNIVERSITY OF ILLINOIS Agricultural Experiment Station BULLETIN No. 204 GERM CONTENT OF MILK II. AS INFLUENCED BY THE UTENSILS BY M. J. PEUCHA, H. M. WEETER, AND W. H. CHAMBERS UEBANA, ILLINOIS, FEBRUARY, 1918 CONTENTS OF BULLETIN No. 204 PAGE 1. INTRODUCTION 217 2. PREVIOUS STUDIES ON UTENSILS '. 218 3. METHODS OF STUDY 219 4. PART I. INFLUENCE SHOWN BY DIRECT EXAMINATION OF UTENSILS 221 Bacteria Found in Freshly Washed Cans 221 Bacteria Found in Cans Thirty Hours after Being Washed 226 Bacteria Found in Cans Washed and Returned to the Farm 229 Sources of Bacteria in Washed Cans 231 Milk as the Source of the Bacteria 231 Wash Water as a Source of the Bacteria 233 Bacteria Found in Bottles Freshly Washed and in Bottles Standing Twenty-four Hours 241 5. PART II. INFLUENCE SHOWN BY EXAMINATION OF THE MILK 245 Collective Influence of Utensils at the Barn 245 Influence of Unsteamed Bottle Filler upon Germ Content of Milk .... 248 Collective Influence of Utensils at the Barn and at the Dairy 250 Influence of Individual Utensils at the Barn and at the Dairy 252 6. SUMMARY 255 7. CONCLUSIONS . ..257 GERM CONTENT OF MILK II. AS INFLUENCED BY THE UTENSILS BY M. J. PEUCHA, ASSISTANT CHIEF IN DAIRY BACTERIOLOGY H. M. WEETER, ASSISTANT IN DAIRY HUSBANDRY, and W. H. CHAMBERS, ASSISTANT IN DAIRY BACTERIOLOGY INTRODUCTION The interval during which milk will remain sweet is an important element of its value, and one for which the producer has been held mainly responsible. iMilk sours because of the growth in it of plant life bacteria. ) The problem of protecting the keeping quality of milk becomes one of preventing the entrance of bacteria, of destroying them after they enter, or of keeping them so cold as to check their growth. The first interest of the producer is to restrict the number of bacteria getting into the milk, so far as is consistent with the costs involved. ; To do this he must know the relative importance of the various avenues thru which they may enter. Additions to our knowledge regarding the relative importance of the various avenues thru which bacteria enter milk have been fur- nished by a series of experiments conducted at the New York (Geneva) 3 and the Illinois 2 Agricultural Experiment Stations. The most striking result of these studies has been to establish the fact that ordinarily barns have little or no measurable influence upon the germ content of the milk produced in them. . The need of further study to determine the mode of entrance of the large number of bacteria that are regularly found in the public milk supply, being recognized, this investigation, begun in the fall of 1913, was directed toward determining the influence that the various utensils in which milk is normally handled exerts upon the germ con- tent of the milk. 'Harding, H. A., Wilson, J. K., and Smith, G. A. Milking Machines : Effect of Method of Handling on the Germ Content of Milk. N. Y. (Geneva) Agr. Exp. Sta, Bui. 317. 1909. Harding, H. A., Wilson, J. K., and Smith, G. A. The Modern Milk Pail. N. Y. (Geneva) Agr. Exp. Sta. Bui. 326. 1910. Harding, H. A., Ruehle, G. L., Wilson, J. K., and Smith, G. A. The Effect of Certain Dairy Operations upon the Germ Content of Milk. N. Y. (Geneva) Agr. Exp. Sta. Bui. 365, pp. 198-233. 1913. Harding, H. A., and Wilson, J. K. A Study of the Udder Flora of Cows. N. Y. (Geneva) Agr. Exp. Sta. Tech. Bui. 27. 1913. Ruehle, G. L. A., and Kulp, W. L. Germ Content of Stable Air and Its Effect upon the Germ Content of Milk. 1ST. Y. (Geneva) Agr. Exp. Sta. Bui. 409, pp. 418- 474. 1915. ^Prucha, M. J., and Weeter, H. M. Germ Content of Milk: I. As Influenced by Factors at the Barn. 111. Agr. Exp. Sta. Bui. 199. 1917. 217 218 BULLETIN No. 204 [February, PREVIOUS STUDIES ON UTENSILS In 1889, H. W. Conn 1 made the following comment on the influence of utensils upon bacterial contamination of milk : x< ' Vessels in which milk and cream are to be kept are a great source of contamination of bacteria. The latter gather upon the sides and in the joints and de- velop in the minute portions of milk, grease, and other matter from which it is difficult to free the vessels completely by washing. ' '^ Five years later H. L. Russell, 2 in his studies on milk contamina- tion, examined two covered pails. One pail was steamed for half an hour and the other was cleaned in the ordinary way but not steamed. The milk received into the sterilized pail had a germ content of 165 bacteria per cubic centimeter, while that received into the pail not steamed contained 4,265 bacteria per cubic centimeter. In commenting later on the contamination of milk by utensils, this author 3 states that ' ' dirty vessels are a prolific source of trouble. ' ' ^ In 1898, Backhaus and Cronheim 4 observed that passing milk over a certain cooler raised its germ content from 11,500 to 33,000 bacteria per cubic centimeter. In 1904, Bergey 5 concluded from his studies on milk contamination that the greater portion of the bacteria with \vhich milk becomes contaminated is derived from the utensils. In the following year, Erf and Melick 6 reported that cream separators flushed with hot water at night after being used, when used the fol- lowing morning added to the germ content of the milk passing thru them, some millions of bacteria per cubic centimeter of milk. In 1906, Stewart 7 reported that the utensils invariably harbor a considerable number of bacteria. He found that' it is difficult to free the utensils from germ life short of treatment with steam under pressure. * Russell and Hoffmann 8 found that when milk bottles were washed and steamed and allowed to stand twenty-four hours, the bacteria multiplied in the remnants of water resulting from the condensation of the steam. , H. W. Bacteria in Milk and Its Products. Storrs Agr. Exp. Sta. Bui. 4. 1889. 2 Russell, H. L. Sources of Bacterial Infection and the Eolation of the Same to the Keeping Quality of Milk. Wis. Agr. Exp. Sta. Ann. Bpt. 11, p. 152. 1894. 'Eussell, H. L. Tainted and Defective Milks: Their Causes and Methods of Prevention. Was. Agr. Exp. Sta. Bui. 62. 1897. 4 B(ackhaus, W., und Cronheim, W. Tiber aseptische Milchgewinnung. Ber. Landw. Inst. Univ. Konigbs., 1, Heft. 2, pp. 12-32. 1898. 5 Bergey, D. H. Sources and Nature of Bacteria in Milk. Penn. Dept. of Agr. Bui. 125. 1904. Erf, O., and Melick, Chas. "W. Care of Dairy Utensils. Kans. Agr. Exp. Sta. Bui. 131. 1905. T Stewart. A. H. Cleansing of Milk Vessels: Eelative Value of Washing Powders. Amer. Med., 2, pp. 241-244. 1906. 8 Eussell, H. L., and Hoffmann, Conrad. Bacteriological Test of Bottle-Wash- ing Device. Wis. Agr. Exp. Sta. Ann. Ept. 22, pp. 227-231. 1905. 1913} GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 219 The various studies upon the milking machines by Harrison, 1 by Hastings and Hoffmann, 2 Stocking and Mason, 3 Meeker, 4 and Harding, Wilson, and Smith 5 have shown that the germ content of milk may be astonishingly increased thru the influence of the milking machine, tho it is possible to keep the influence of the machine within fair limits provided it is properly handled. METHODS OF STUDY MT "Washing of Utensils. The cans used in this study were from two different dairies. In both dairies the method of washing was similar in that each can was placed in a vat containing one-percent warm solution of sodium-carbonate washing powder, and scrubbed with a brush. There were, however, some differences in the conditions and in the methods employed in the two dairies. In Dairy A the milk handled in the cans had usually a low germ content ; the number of cans washed in the same lot of wash water was from 20 to 30; the amount of wash water used was 60 gallons, and the cans were rinsed after being washed. In Dairy B the milk handled in the cans invaria- bly had a high germ content ; from 60 to 80 cans were washed in the same lot of wash water ; the amount of the water used was about 25 gallons, and the cans were not rinsed after they were washed. All other utensils studied were washed in Dairy A. In the case of some of the utensils, such as the bottle filler, the above method of washing could not be employed ; and in some of the experiments with cans, the method of washing was intentionally altered. Such changes are described in connection with the respective experiments. The cans in Dairy A were of eight-gallon capacity ; those in Dairy B were of five-, eight-, or ten-gallon capacity ; and the bottles were the regular quart size. Determining Number of Bacteria in Utensils. Two methods were used in this study for determining the number of bacteria in the uten- sils. In the experiments reported in Part I a given quantity of sterile water, usually one liter, was poured into the utensil and after a thoro shaking, a sample of this water was taken and the number of bacteria Garrison, F. C. Machine Drawn Versus Hand Drawn Milk. Centbl. Bakt. (etc.), 2 Abt., 5, 183-189. 1899. "Hastings, E. G., and Hoffmann, Conrad. Bacterial Content of Machine Drawn and Hand Drawn Milk. Wis. Agr. Exp. Sta. Ann. Ept. 24, pp. 214-223. 1907. 'Stocking, W. A., Jr., and Mason, C. J. Milking Machines: Part I. Effect upon Quality of Milk. Storrs Agr. Exp. Sta. Bui. 47. 1907. 4 Meeker, E. B. Bacterial Efficiency of the Milking Machine. Penn. Agr. Exp. Sta. Ann. Ept. for the year 1907-1908, Part II. pp. 146-159. 1908. "Harding, H. A., Wilson J. K., and Smith, G. A. Milking Machines: Effect of Method of Handling on the Germ Content of Milk. N. Y. (Geneva) Agr. Exp. Sta. Bui. 317. 1909. 220 BULLETIN No. 204 [Felruary, in it determined. This obviously falls considerably short of demon- strating the full amount of germ life present in the utensils. In the experiments reported under Part II, samples were taken of the milk after it was actually poured into the utensils in the ordinary opera- tions of the dairy, and the difference in the germ content of the milk handled in steamed utensils and that handled in unsteamed utensils was taken as the measure of the germ content of the unsteamed uten- sils. This method evidently more closely measures the true influence of the utensils upon the milk, but it is ordinarily a more difficult and expensive form of experimentation. The plate method was used for counting the bacteria in these sam- ples. Usually two or three dilutions were made from each sample, and three plates were poured from each dilution. Every count recorded in this study is an average of the counts from at least three plates. The medium used in making these counts had the following composition: Agar shreds 15 grams Liebig 's meat extract 3 grams Witte 's peptone 10 grams Lactose 10 grams Distilled water 1 liter The reaction of this medium was adjusted to one percent normal acid to phenolphthalein. The plates were incubated seven days : five days at 20 C. and two days at 37 C. It should be understood that this method of counting the bacteria does not show the total number present. It was used because among the available methods of making such determinations this one seemed best suited to the problem. 1918] GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 221 PART I. INFLUENCE SHOWN BY DIRECT EXAMINATION OF UTENSILS Six experiments are recorded in this part of the study, five of them devoted to cans and one to bottles. The aim in these experi- ments was, first, to determine the number of bacteria in freshly washed but unsteamed cans and bottles ; second, to determine whether bacteria increase in utensils that are washed and then kept for a period of time before being filled with milk ; and third, to determine the source of these bacteria. BACTERIA FOUND IN FRESHLY WASHED CANS This experiment included a study of 170 cans that had been used in shipping sweet milk from the farm to the dairy. The cans re- ported upon in Tables 1, 2, and 3 came to Dairy A from three differ- ent farms, and those in Table 4 came to Dairy B from thirty-four different farms. In both dairies the cans were washed immediately after the milk was poured from them. The methods of washing fol- lowed in these two dairies and the method of determining the germ life remaining in the cans have already been described (page 219). The length of time intervening between the washing of the cans and the plating of the water with which^they were rinsed varied from one- half to four hours. That such rinsing did not remove all the bacteria from the uten- sils is self evident. In this experiment, therefore, an attempt was also made to determine approximately the accuracy of the method. For this purpose each can in Tables 1, 2, and 3 was rinsed more than once, and the relation between the number of bacteria removed by the first rinsing and that removed by subsequent rinsings was calculated. The cans in Table 1 were rinsed twice with 1,000 and 1,500 cc. of sterile water, respectively; those in Table 2 were rinsed four times with successive one-liter portions of sterile water; those in Table 3 were rinsed four times with successive two-liter portions of sterile .water ; and those in Table 4 were rinsed once with one liter of sterile water. ^Calculations are also presented which show what the increase in the germ content of milk would have been had the total number of bacteria removed from each can been added to a can of milks Arhe results of this experiment are significant in that the numbers of bacteria removed from the washed cans by rinsing them with a small quantity of sterile water were large and variable./ More than one billion bacteria were removed from each of 39 of the 114 cans washed in Dairy A, and from each of 38 others the number was more than one hundred million. Even larger numbers were removed from the 56 cans washed in Dairy B ; in which dairy, it will be recalled, the 222 BULLETIN No. 204 [February, milk as it was received had a higher germ content than that received at Dairy A, a greater number of cans were washed in a smaller amount of water, and the cans were not rinsed after being washed. More than one billion bacteria were removed from each of 42 of the cans in this dairy, and in only 4 cans was the number smaller than one hundred million. The largest number removed from a single can in either dairy was 96,666,000,000, and the smallest was 5,981,000. The influence of such large numbers of bacteria on the milk may be estimated approximately by calculating the increase in the germ content of a can of milk if these numbers were added to it. The two above cans with the maximum and minimum numbers were of ten- and eight-gallon capacity, respectively. If the minimum number, 5,981,- 000 bacteria, were added to eight gallons of milk, its germ content TABLE 1. NUMBER OF BACTERIA IN FRESHLY WASHED CANS, AS DETERMINED BY Two SUCCESSIVE EINSINGS: DAIRY A No. of can Number of bacteria removed by each rinsing Total number of bacteria removed Increase in germ content of can of milk, per cc. Percentage of bacteria removed by 1st rinsing Binsed with 1,000 cc. of sterile water Einsed with 1,500 cc. of sterile water 1 16 400 000 547 000 16 947 000 559 97 2 16 560 000 530 000 17 090 000 564 97 3 38 840 000 3 370 000 42 210 000 1394 92 4 14 570 000 680 000 15 250 000 503 96 5 229 750 000 11 320 000 241 070 000 7960 95 6 312300000 33 500 000 345 800 000 11425 90 7 9 157 000 000 810 000 000 9 967 000 000 329 100 92 8 603 400 000 122 000 000 725 400 000 23950 83 9 61 000 000 1 500 000 62 500 000 2064 98 10 61 360 000 1 550 000 62 910 000 2097 98 11 13 000 000 000 1877000000 14 877 000 000 491 300 87 12 681 400 000 308 600 000 990 000 000 32700 69 13 16 040 000 812 000 16 852 000 556 95 14 50 470 000 2 412 000 52 882 000 1746 95 15 168 800 000 30 000 000 198 800 000 6564 85 16 83 560 000 19 500 000 103 060 000 3404 81 17 20 580 000 000 3 150 000 000 23 730 000 000 783 600 87 18 40 280 000 12 075 000 52 355 000 1729 77 19 2-0 940 000 1 102 000 22 042 000 727 95 20 52 000 000 2 467 000 54 467 000 1799 95 21 3 986 500 000 317000000 4 303 500 000 142 150 93 22 4 898 000 000 485 000 000 5 383 000 000 177 750 91 23 1 212 000 000 57 700 000 1 269 700 000 41930 95 24 4 302 000 000 362 000 000 4 664 000 000 154 000 92 25 2 413 000 000 213 000 000 2 626 000 000 86720 92 26 5 324 000 000 370 000 000 5 694 000 000 188 000 94 27 145 950 000 30 775 000 176 725 000 5836 83 28 104 500 000 60 200 000 164 700 000 5439 63 29 7 631 000 000 1120000000 8 751 000 000 289 000 87 30 80 640 000 11 125 000 91 765 000 3030 8-8 31 123 500 000 58 750 000 182 250 000 6018 68 32 33 290 000 3 130 000 36 420 000 1202 91 1918} GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 223 TABLE 2. NUMBER OF BACTERIA IN FRESHLY WASHED CANS, AS DETERMINED BY FOUR SUCCESSIVE EINSINGS WITH ONE LITER OF STERILE WATER: DAIRY A No. of can Number of bacteria removed by Total number of bacteria removed Increase in germ content of can of milk, per cc. Percent- age of bacteria removed by 1st rinsing 1st rinsing 2d rinsing 3d rinsing 4th rinsing 1 339 633 000 61767000 33 133 000 21 119 000 455 652 000 15 048 75 2 10 466 000 1271000 589 000 282 000 12 608 000 416 83 3 796 499 000 190 299 000 143 299 000 60 826 000 1 190 923 000 39324 67 4 34 733 000 6 433 000 2 378 000 160 000 43 704 000 1443 79 5 11 366 O'OO 959 000 244 000 161 000 12 730 000 420 89 6 19 433 000 893 000 999 000 173 000 21 498 000 709 90 7 16 700 000 1 360 000 618 000 411 000 19 089 000 630 87 8 514 500 000 243 300 000 157 660 000 61 000 000 976 460 000 32245 53 9 20 850 000 1 520 000 259 000 185 000 22 814 000 753 91 10 427 850 '000 60 000 000 25 830 000 19 466 000 533 146 000 17600 80 11 2 863 333 000 701 716 000 436 000 000 37 666 000 4 038 715 000 133 370 71 12 95 000 000 5 500 000 1 700 000 1 266 000 103 496 000 3418 92 13 29 233 000 6 096 000 2 919 000 1 932 000 40 180 000 1326 73 14 6 549 333 000 633 088 000 489 166 000 302 213 000 7 973 800 000 263 300 82 15 64 400 000 11 300 000 6 338 000 3 200 000 85 238 000 2814 78 16 86 150 000 22 400 000 10 900 000 6 516 000 125 966 000 4159 68 17 2 800 000 1 800 000 989 000 382 000 5 981 000 197 47 18 18 800 000 3 190 000 2 541 000 1 246 000 25 777 000 851 73 19 2 370 000 000 1 216 000 000 706 100 000 44 244 000 4 336 344 000 143 170 55 20 668 000 000 199 600 000 95 150 000 50 600 000 1 013 350 000 33450 66 21 88 000 000 15 150 000 5 890 000 1 244 000 110 284 000 3639 80 22 175 000 COO 26 900 000 18 560 000 14 195 000 234 655 000 7747 . 75 23 368 000 000 83 000 000 49 200 000 27 900 000 528 100 000 17430 70 24 3 620 000 000 890 000 000 3.32 300 000 20 200 000 4 882 500 000 161 200 74 25 2 170 '000 000 416 000 000 304 600 000 342 930 000 3 233 530 000 106 800 67 26 1 610 000 000 171 000 000 82 000 000 37 000 000 1 900 000 000 62 740 85 27 97 450 000 9 475 000 10 870 000 5 570 000 123 365 000 4075 79 28 20 133 000 000 2 843 000 000 886 600 000 895 000 000 27 757 000 000 916 600 73 29 403 500 000 59 850 000 52 800 000 27 900 000 544 050 000 17965 74 30 3 590 000 000 715 000 000 174 700 QOO 150 100 000 4 629 800 000 152 990 78 31 525 500 000 51 500 000 28 400 000 22 100 000 627 500 000 20740 84 32 159 500 000 14 100 000 5 120 000 3 040 000 181 760 000 6002 88 33 222 000 000 14 400 000 6 825 000 3 800 000 247 025 000 8156 90 34 7 650 000 000 2 720 000 000 314 200 000 410 700 000 11 094 900 000 366 400 69 35 1 330 000 000 134 350 000 49 700 000 39 800 000 1 553 850 000 51320 86 36 1 557 000 000 125 500 000 91 900 000 39 933 000 1 814 333 000 59900 86 37 222 000 000 15 000 000 6 485 000 3 700 000 247 185 000 8161 90 38 32 930 000 000 918 000 COO 377300000 36 888 000 34 262 180 000 1 131 000 96 39 109 333 000 98 667 000 61 600 000 57 533 000 327 133 000 10 800 33 40 561 333 000 171 667 000 73 400 000 554 000 806 954 000 26710 69 41 78 133 000 23 983 000 11 750 000 6 010 000 119876000 3958 65 42 2 150 667 000 431 333 000 201 000 000 125 000 000 2 908 000 000 96040 74 43 154 000 000 78 867 000 43 467 000 28 866 000 305 200 000 10080 51 44 216 000 000 70 667 000 19 633 000 21007000 327 367 000 10810 66 45 528 666 000 47 044 000 28367000 29 833 000 633 910 000 20930 83 46 350 000 000 77 933 000 35 000 000 30 733 000 493 666 000 16300 71 47 1 036 667 000 286 667 000 119600000 84 133 000 1 427 007 000 47120 73 48 1 710 000 000 612007000 219033000 180 750 000 2 722 450 000 89800 63 49 1 935 333 000 461 333 000 209 533 000 158 667 000 2 764 866 000 91300 70 50 2 720 '000 000 756 000 000 213 200 000 272 000 000 3 961 200 000 130 800 69 224 BULLETIN No. 204 [February, would be increased by 197 bacteria per cubic centimeter. If 96,666,- 000,000 bacteria, the maximum number found in a single can, were added to ten gallons of milk, its germ content would be increased by 2,557,000 bacteria per cubic centimeter. If all the bacteria removed from the 32 eight-gallon cans listed in Table 1 were added to 256 gallons of milk (the total capacity of the cans), its germ content would be increased by 87,657 bacteria per cubic centimeter. Corresponding calculations for Tables 2, 3, and 4 would show an average increase in the germ content of the milk, of 87,059, 47,863, and 291,790 bacteria, respectively. Of the 170 cans recorded in these tables, 54, or 31.8 percent, would have added more than 100,000 bacteria per cubic centimeter of milk ; TABLE 3. NUMBER OP BACTERIA IN FRESHLY WASHED CANS, AS DETERMINED BY FOUR SUCCESSIVE EINSINGS WITH Two LITERS OF STERILE WATER : DAIRY A No. of can Number of bacteria removed by Total number of bacteria removed Increase in germ content of can of milk, per ce. Percent- age of bacteria removed by 1st rinsing 1st rinsing 2d rinsing 3d rinsing 4th rinsing 1 35 334 000 2 466 000 f 1 466 000 1066000 40 332 000 1331 87 2 122 666 000 18 866 000 17 000 000 12 068 000 170 600 000 5634 72 3 374 666 000 192 666 000 109 334 000 104 666 000 781 332 000 25800 48 4 300 000 000 87000000 33 466 000 33 614 000 454 200 000 14990 66 5 28 666 000 4 666 000 2 666 000 1 066 000 37 064 000 1224 77 6 5 146 666 000 1 888 000 000 1 237 334 000 858 666 000 9 130 666 000 301 500 56 7 40 666 000 1 134 000 600 000 334 000 42 534 000 1404 95 8 111 000 000 13 666 000 7868000 4 634 000 137 168 000 4530 81 9 25 334 000 2 400 000 934 000 932 000 39 600 000 1307 85 10 37 666 000 5 000 000 2000000 1 800 000 45 466 000 1502 80 11 1 746 666 000 320 000 000 233 334 000 148 666 000 2 448 666 000 80840 71 12 1 016 666 000 238 666 000 263 334 000 138 968 000 1 657 634 000 54720 61 13 594 666 00-0 282 000 000 179 600 000 151066000 1 207 332 000 39880 49 14 80 666 000 8 200 000 2 866 000 2 068 000 93 800 000 3098 86 15 54 666 000 1 200 000 1 532 000 466 000 57 864 000 1910 94 16 5 310 000 000 997 000 000 536 000 000 414 666 000 7 357 666 000 242 960 73 17 46 000 000 2 934 000 600 000 532 000 50 066 000 1652 92 18 234 000 000 4 414 000 3 800 000 934 000 293 268 000 9685 96 19 4 320 000 000 714 000 000 582 000 000 351334000 5977334000 197 080 72 20 13 334 000 1 800 000 1 266 000 400 000 16 800 000 554 79 21 42 666 000 2 344 000 724000 466 000 46 200 000 1524 92 22 78 000 000 7 866 000 3 266 000 2 334 000 91 466 000 3020 85 23 3 186 666 000 574 000 000 466 000 000 354 000 000 4 780 666 000 157 840 71 24 78 666 000 6 800 000 4 400 000 2 734 000 92 600 000 3058 85 25 2500000000 462 666 000 327 000 000 194 000 000 3 483 666 000 115 020 72 26 766 666 000 186 000 000 204 134 000 45 600 000 1 203 000 000 39740 64 27 55 000 000 4 534 000 2 134 000 2 400 000 64 068 000 2116 86 28 322 666 000 41 334 000 18 000 000 20 066 000 402066000 13274 80 29 637 000 000 128*14000 64 034 000 58 168 000 888 136 000 29320 72 30 170 666 000 8 400 000 10 600 000 3 600 000 193 266 000 6384 88 31 78 666 000 7 066 000 1 800 000 1 800 000 89 332 000 2950 88 32 3 226 666 000 928 666 000 575 334 000 293 334 000 5 004 000 000 365220 64 GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 225 54 would have added more than 10,000 and less than 100,000 bacteria; and 62 cans, or 36.4 percent, would have added less than 10,000. The data in Tables 1, 2, and 3 demonstrate that when milk cans are rinsed more than once, the first rinsing always removes a larger number of bacteria than any subsequent single rinsing. When four rinsings were made in succession, in 78 out of 82 cases the first rinsing alone removed more bacteria than all three subsequent rinsings. The data also indicate, with only fifteen exceptions, that any one of the consecutive rinsings of a can removes more bacteria than any subse- quent rinsing. If the total number of bacteria removed from each can by all the rinsings is taken as 100 percent, the calculations will show that from 110 of the 114 cans the first rinsing removed more than 50 percent of the bacteria. The highest percentage removed by the first rinsing was 97, and the lowest was 33. The average percentage removed by the first rinsing of the cans rinsed only twice, once with 1,000 cc. and once with 1,500 cc. of water (Table 1), was 89; for the cans rinsed TABLE 4. NUMBER OF BACTERIA IN FRESHLY WASHED CANS, AS DETERMINED BY ONE EINSING WITH ONE LITER OF STERILE WATER: DAIRY B No. of can Capac- ity, gal. Number of bacteria re- moved by rinsing Increase in ?erm content of can of milk, per cc. No. of can Capac- ity, gal. Number of bacteria re- moved by rinsing Increase in germ content of can of milk, per cc. 1 5 7 360 000 000 389 400 29 10 7 133 000 000 188 700 2 8 I 960 000 000 64730 30 5 30 000 000 000 1587300 3 8 490 000 '000 16180 31 10 17 466 000 000 462 080 4 10 3 680 000 000 97350 32 5 1 853 000 000 98040 5 5 1 430 '000 000 75660 33 10 96 666 000 000 2 557 000 6 8 1 390 000 000 45900 34 8 886 000 000 29260 7 8 1 590 000 000 52500 35 5 4 366 000 000 231 000 8 5 5 690 000 000 301 050 36 5 806 000 000 42640 9 5 222 000 000 11740 37 8 60 000 000 1981 10 8 2 310 000 000 76290 38 5 90 000 000 4760 11 . 8 2 940 000 000 97100 39 8 2 240 000 000 73970 12 8 11070000000 353360 40 5 2 486 000 000 131 540 13 10 8 550 000 000 226 180 41 8 8 883 000 000 293 360 14 8 38 670 000 000 1 277 000 42 8 190 000 000 62740 15 8 8 730 000 000 288 300 43 5 1 500 000 000 79360 16 5 1 596 000 000 84450 44 5 2 690 000 000 142 330 17 10 330 000 000 8730 45 8 143'000 000 4722 18 8 7 446 000 000 245 900 46 8 2 533 000 000 83650 19 5 8 860 000 000 468 800 47 10 14 000 000 000 370 300 20 8 8 566 000 000 282 880 48 8 6 200 000 000 204 740 21 5 736 000 000 38940 49 5 4 186 000 000 221 480 22 5 250 000 000 13230 50 8 18 830 000 000 621 800 23 5 256000000 13540 51 10 9 133 000 000 241 600 24 5 2 560 000 000 135 450 52 8 19 666 000 000 649 400 25 5 16 360 000 000 865 600 53 10 11 233 000 000 297 150 26 5 83 000 000 4390 54 8 66 000 000 2179 27 5 2 106 000 000 109 000 55 8 3 100 000 000 102 370 28 5 23 660 000 000 1 251 800 56 8 3 160 000 000 104 350 226 BULLETIN No. 204 [February, four times with one liter of water (Table 2), it was 74.6 ; and for the cans rinsed four times with two liters of water (Table 3), it was 77. The results of these observations on 170 cans suggest that milk cans when washed in the ordinary manner contain sufficient germ life to heavily inoculate the milk later placed in them. The results of successive rinsings with sterile water suggest that while the germ life removed by the first rinsing amounts to a considerable fraction of the germ life in the can, it is by no means the entire germ life present. Accordingly, the germ content as determined in this manner is dis- tinctly below the true number of bacteria actually present in the uten- sil under investigation. BACTERIA FOUND IN CANS THIRTY HOURS AFTER BEING WASHED In the preceding experiment it was shown that freshly washed cans invariably harbored large numbers of bacteria. In dairy practice the utensils, however, are not commonly used for milk immediately after they are washed. This is especially true of cans in which milk is shipped from the farm to the dairy. Such cans are washed and usually steamed at the dairy ; then covered with the lids and returned to the farm, where they are frequently used for milk without any further treatment. At times, one or even two days will elapse be- tween the washing of the cans and their use. f This experiment was designed, therefore, to determine the germ life in cans at the time they would ordinarily be used. % Thc 160 eight- gallon cans examined were washed in Dairy A. One hundred of these were steamed, while sixty were left unsteamed. The steaming consisted of holding each can over a jet of steam at 15 pounds pressure for 25 seconds. The pressure of the steam was measured by a gage placed between the valve and the' jet opening. Other experiments upon steaming cans in this manner showed that if cans so treated were filled with milk immediately afterward,, they rarely added more than 2 bacteria per cubic centimeter to the milk. Fifty of the steamed cans and fifty of those not steamed were inverted en a rack with the lids off. The other fifty steamed cans and the ten not steamed were closed immediately after washing. All the cans were then kept th'irty hours in a room having a humidity of 40 per- cent and a temperature of 60 to 70F. The number of bacteria found in each can is shown in Table 5. The fifty cans that were washed, steamed, and then held thirty hours uncovered and inverted on a rack were dry and free from bad odor. The number of bacteria found in them was small in all cases. Only 3 of the fifty cans had more than one million bacteria and 36 of them had less than 100,000. If the bacteria found in these fifty cans were added to 400 gallons of milk, the germ content of this 1918} GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 227 TABLE 5. NUMBER OF BACTERIA IN STEAMED AND IN UNSTEAMED CANS HELD THIRTY HOURS AFTER TREATMENT: DAIRY A (As determined by rinsing with one liter of sterile water) Steamed cans held 30 hours Unsteamed cans held 30 hours Uncovered and inverted on a rack Covered with their lids Uncovered and inverted on a rack Covered with their lids No. of can No. of bacteria No. of can No. of bacteria No. of can No. of bacteria No. of can No. of bacteria 1 20000 51 10000 101 164 000 000 151 6 910 000 000 2 20000 52 60000 102 148 000 000 152 5 520 000 000 3 20000 53 66 000 000 103 6 000 000 153 4 150 000 000 4 30000 54 6 800 000 104 170-000 000 154 4 300 000 000 5 30000 55 3 260 000 105 190 '000 000 155 6 000 000 000 6 20000 56 15 000 000 106 17 000 000 000 156 2 1-00 000 000 7 40000 57 10 600 000 107 7 300 000 000 157 1 400 000 000 8 10 '000 58 11 600 000 108 44 000 000 158 6 250 000 000 9 20000 59 21300000 109 3 000 000 159 1 900 '000 000 10 240 000 60 220 000 110 22 000 '000 160 450 000 000 11 100 000 61 60 000 000 111 10 100 000 000 12 290 000 62 210 000 112 1 000 O'OO 13 700 000 63 110 000 113 135 000 000 14 40000 64 30000 114 1 000 000 15 60000 65 2 13 000 '000 115 303 '000 000 16 600-00 66 39 000 000 116 76000000 17 600 000 67 550 000 117 8 000 000 18 1 450 000 68 48 000 000 118 9 000 O'OO 19 50000 69 14 100 000 119 94 000 000 20 430 '000 70 2 180 000 120 59 000 000 21 90000 71 2 260 000 121 14 000 000 22 30000 72 4 800 000 122 3 000 O'OO 23 30000 73 210 000 123 42 000 000 24 5000-0 74 110 000 000 124 22 000 000 25 330 000 75 14 500 000 125 278 000 000 26 150 000 76 210 '000 126 4 700 000 000 27 90000 77 35 500 000 127 48 000 000 28 30000 78 7 000 000 128 2 000 000 29 80000 79 1 310 000 129 10 000 000 30 30000 80 35 '000 000 130 21 000 000 31 30000 81 130 000 131 8 000 000 32 60000 82 4 380 000 132 1 000 000 33 50000 83 78 000 000 133 1 000 000 34 90000 84 240 000 134 17 000 O'OO 35 60000 85 12 500 000 135 1 000 000 36 20 000 86 89 000 000 136 48 000 000 37 2 720 000 87 43 000 000 137 1 000 000 38 30000 88 1 190 000 000 138 3 000 000 39 120 000 89 33 000 000 139 1 000 000 40 30 000 90 67 000 000 140 3 000 '000 41 3 700 000 91 240 000 141 2 000 000 42 100 000 92 50 000 000 142 2 000 000 43 50000 93 270 000 000 143 43 000 000 44 20 000 94 240 000 144 2 000 000 228 BULLETIN No. 204 [February, TABLE 5. Concluded Steamed cans held 30 hours Unsteamed cans held 30 hours Uncovered and inverted on a rack Covered with their lids Uncovered and inverted on a rack Covered with their lids No. of can No. of bacteria No. of can No. of bacteria No. of can No. of bacteria No. of can No. of bacteria 45 30000 95 149 000 000 145 5 000 000 46 40000 96 710 000 146 2 000 000 47 330 000 97 590 000 147 2 000 000 . 48 80000 98 16 000 000 148 3 000 000 49 60 000 99 550 000 149 5 000 000 50 30000 100 22 000 000 150 170 000 Average no. of bacteria per can 255,800 54 988 000 822 463 400 3 898 000 000 Average no. of bacteria per cc. in can of milk 8 1816 27164 128 730 amount of milk would be increased by 8 bacteria per cubic centi- meter. Whether any bacterial growth took place in these cans during the thirty hours is not certain, but the results show that cans so treated have a negligible effect upon the germ content of milk. The fifty cans that were washed, steamed, and then held thirty hours with the lids on, were still wet and most of them had a more or less pronounced odor. These cans had a much larger number of bacteria than those steamed, uncovered, and inverted. Only 3 of the fifty cans had less than 100,000 bacteria, and in 34 the number was over one million. If the bacteria found in these fifty eight-gallon cans were added to 400 gallons of milk, its germ content would be increased by 1,816 bacteria per cubic centimeter. The fifty cans that were washed but not steamed and were then held thirty hours uncovered and inverted, were dry. None of the cans had a bad odor, altho most of them were not what is called "sweet smelling." The number of bacteria in them was much larger than in the cans steamed and inverted. Only one of the fifty cans had less than one million bacteria, in 24 of them the numbers of bacteria were be- tween one million and ten 'millions, and 4 cans had over a billion bacteria each. If the bacteria found in all these cans were added to 400 gallons of milk, its germ content would be increased by 27,164 bacteria per cubic centimeter. It is, however, to be observed that this average number does not give an accurate idea of the condition of these cans since the total number of bacteria found in the fifty cans was 41,123,170,000, and of this number 39,100,000,000 were contri- buted by only 4 cans and 2,023,170,000 by the remaining 46 cans. The 191S] GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 229 germ content of milk in these 46 cans would have averaged only 1,336 bacteria per cubic centimeter. The destructive effect of the drying of the cans upon the germ life in them is evident from a comparison of these results with those obtained from the freshly washed cans reported in Tables 1, 2, and 3. The ten cans that were washed but not steamed and then were covered and held thirty hours had in all cases a decidedly bad odor and they also contained large numbers of bacteria. Nine of the ten cans showed over a billion bacteria each. If the total number of bacteria found in these ten eight-gallon cans were added to 80 gallons of milk, its germ content would have been increased by 128,730 bacteria per cubic centimeter. f It is evident from these results that pronounced bacterial growth took place in the cans that were covered and allowed to stand for thirty hours. Bacterial growth in general is conditioned by three factors : temperature, food, and moisture, jf All -the cans in this ex- periment were held at the same temperature and were washed in the same dairy by the same operator, so that the principal difference be- tween the covered and the uncovered cans was the persistance of moisture in the covered cans. These results point to the conclusion that it is very difficult to wash cans so that no bacterial food is left in them, and if the cans are then covered without being dried, and are allowed to stand for a period of time, the bacteria in them increase to large numbers. BACTERIA FOUND IN CANS WASHED AND RETURNED TO THE FARM This experiment was designed to measure the germ life in cans that were washed and returned to several dairy farms ready for use/ In order to maintain the usual conditions in this dairy (Dairy A), no interference was made in any of the usual operations and the men doing the- work were not aware of the experiment. No record could be obtained of the exact treatment of the individual cans, but in gen- eral each can was washed, rinsed, steamed over a jet, and covered with a lid. Casual observations indicated that the steaming of the cans varied from five to twenty seconds per can. The treatment of the cans at the farms was not uniform. At times they were inverted on a rack, with lids off, and at other times they were not opened until used. The time intervening between the wash- ing of the cans and their use varied from six to forty hours. Just before the cans were used for milk they were rinsed with one liter of sterile water and the germ content of this water was de- termined. Table 6 presents the results of the examination of 91 cans. As in the other experiments, the numbers of bacteria found in these cans were varied and in some cases large. Can 43, for example, showed 80.000 bacteria, and Can 66 showed 30,830,000,000 bacteria. Of the 230 BULLETIN No. 204 [February, TABLE 6. NUMBER OF BACTERIA IN CANS AFTER THEY WERE WASHED AND STEAMED IN THE DAIRY AND EETURNED TO THE FARM: DAIRY A (As determined by rinsing with one liter of sterile water) No. of can Number of bacteria in cans Increase in germ content of can of milk, per ce. No. of can Number of bacteria in cans Increase in germ content of can of milk, per cc. 1 56 950 000 1880 47 133 833 000 4420 2 636 500 000 21020 48 47 750 000 1577 3 388 000 000 12870 49 149 000 000 4920 4 1 400 000 46 50 675 000 000 22290 5 1 400 000 46 51 10 950 000 000 361 600 6 1 505 000 000 49 700 52 995 000 000 32860 7 107 500 000 3555 53 83 100 000 2744 8 4 550 000 150 54 520 000 000 17170 9 74750000 2468 55 16 720 000 552 10 42 700 000 1387 56 168 700 000 5570 11 26400000 871 57 19 570 000 646 12 21300000 703 58 26 500 000 875 13 11 375 000 375 59 90 640 000 2993 14 80 650 000 2633 60 988 000 30 15 37 000 000 1222 61 39 900 000 1317 16 162 025 000 5320 62 1 187 000 000 39190 17 37 225 000 1229 63 1 900 000 62 18 55 075 000 1819 64 1 949 000 000 64340 19 82 000 000 2708 65 581 000 000 19200 20 24 975 000 825 66 30 83-0 000 000 1 018 000 21 37 325 000 1233 67 30 280 000 1000 22 488 000 000 16110 68 82 900 000 2737 23 400 000 000 13210 69 41 025 000 1355 24 20 500 000 677 70 68 850 000 2273 25 36 000 000 1187 71 51 960 000 1716 26 102 000 000 3368 72 62 900 000 2077 27 22 -000 000 726 73 125 350 000 4140 28 17 000 000 561 74 56 210 000 1856 29- 2 045 000 000 67530 75 80 030 000 2642 30 382 000 000 12610 76 . 40 000 000 1340 31 63 500 000 2097 77 112 700 000 3722 32 36 000 000 1189 78 59 050 OO'O 1950 33 83 000 000 2742 79 506 700 000 16730 34 5 500 000 187 80 79 070 000 2611 35 4 500 000 148 81 28 820 000 951 36 354 500 000 11 700 82 1 698 000 000 56070 37 42 000 000 1387 83 42 730 000 1411 38 3 270 000 000 108 000 84 351 750 000 11611 39 200 000 7 85 17 320 000 572 40 18 766 000 620 86 46 270 000 1527 41 22 750 '000 751 87 173 750 000 5734 42 75 166 000 2482 88 80 060 000 2644 43 80000 3 89 432 000 000 14260 44 59 425 000 1963 90 1 015 000 000 33530 45 85 300 000 2817 91 6 530 000 215 46 44 716 000 1476 91 cans examined, 3, or 3.3 percent, showed less than one million bacteria ; 57 cans, or 62.6 percent, showed between one million and one hundred million bacteria ; and 31, or 34.1 percent, showed over one hundred million bacteria. 1918} GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 231 If the number of bacteria found in Can 43 were added to eight gallons of milk (the capacity of the can), the germ content of the milk would be increased by 3 bacteria per cubic centimeter; in the case of Can 66 it would be increased by 1,018,000 bacteria. If all the bacteria found in the 91 cans were added to 728 gallons of milk (the total capacity of these cans), the germ content of this milk would be increased by 23,523 bacteria per cubic centimeter. These cans were inspected prior to the bacteriological examination and were found to be free from any dirt and in most cases dry. It is impossible to state with certainty whether they were in a better or in a worse condition than the cans used for milk on farms in gen- eral. However, from somewhat extensive inspection of cans on a large number of farms and in dairies, the authors are of the opinion that these 91 cans were cleaner and in a better condition than the average can used for milk. SOURCES OF BACTERIA IN WASHED CANS The results already presented show that there are large numbers of bacteria in freshly washed cans, and that in some cans the num- bers are extremely large. Two of the possible sources of these large numbers of bacteria are the milk that was previously in the can and the water in which the can was washed. Milk as the Source of the Bacteria In this experiment samples for bacteriological study were taken from the milk of each of 153 cans. The cans were then emptied and washed and the number of bacteria in them was determined. The re- sults of these examinations are given in Tables 7, 8, and 9. An examination of these tables shows that the germ content of the milk in the cans, as it arrived at the dairies, was much higher in Dairy B than in Dairy A. The number of bacteria in the cans after they were emptied and washed was likewise higher in Dairy B than in Dairy A. When, however, the comparison is confined to the in- dividual cans in the same "dairy, the relation between the germ con- tent of the milk of a given can and the number of bacteria found in the can after it was emptied and washed, is not so evident. In a few cases, as is seen especially in the results from the cans numbering 85 to 106, a certain relation does exist, but in most cases it is not dis- cernable. How many of the bacteria found in a given washed can came from the milk held by the can previous to washing would naturally depend on the germ content of the milk and also on the amount of the milk left in the can after it was washed. It is self evident that after the 232 BULLETIN No. 204 [February, TABLE 7. GERM CONTENT OF MILK IN THE CANS, AND NUMBER OF BACTERIA IN THE CANS AFTER THEY WERE WASHED (Bacteria in cans determined by rinsing with one liter of sterile water) No. of can Germ content of milk in cans, per cc. No. of bacteria in the can after being washed No. of can Germ content of milk in cans, per cc. No. of bacteria in the can after being washed Dairy A 1 380 000 214000000 21 1400 5 900 000 2 342 000 60 000 000 22 1100 5 900 000 3 298 000 2 000 000 23 1000 7 400 000 4 175000 9 000 000 24 21200 2 000 000 5 51000 2 000 000 25 10 000 700 000 6 51000 1 000 000 26 8800 500 000 7 48000 2000000 27 7200 700 000 8 13000 2 O'OO 000 28 3600 2 000 000 9 4900 2 000 000 29 2300 2 600 000 10 5300 5 000 000 30 1300 800 000 11 3400 15 000 000 31 1100 4 900 000 12 213 000 9 000 000 32 59800 3 200 000 13 178 000 8 900 000 33 40300 3 600 000 14 176 000 9 100 000 34 23 600 363 000 000 15 152000 6 800 000 35 16700 9 100 000 16 130 000 3 400 000 36 11400 3 300 000 17 18000 6 300 000 37 3600 7 000 000 18 7400 4 400 000 38 1900 3 200 000 19 4-000 14 300 000 39 1800 4 500 000 20 2500 10 100 000 40 1000 3 800 000 Dairy B 41 101 300 000 113 670 000 000 74 40000 430 000 000 42 52 000 000 49 330 000 '000 75 ' 2 210 000 1 690 000 000 43 40 800 000 4 100 000 000 76 300 000 4 440 000 000 44 33 500 000 13 400 000 000 77 5520000 30 400 000 000 45 18 170 000 2 870 000 O'OO 78 350 000 18 650 000 000 46 18 000 000 6 060 000 000 79 10 830 000 5 670 000 000 47 13 200 000 7 970 000 000 80 14 500 000 8 400 000 000 48 9 370 000 930 000 OO'O 81 2 750 000 70 660 000 000 49 6 920 000 4 900 000 000 82 1 390 000 104 330 000 000 50 6 600 000 2 220 000 000 83 290 000 21 800 000 000 51 5 460 000 8 000 000 000 84 9 500 000 720 000 000 52 5 270 000 330 000 000 85 10000 140 000 000 53 4530000 51 330 000 000 86 550 000 1 200 000 000 54 4 490 000 1 660 000 000 87 1 970 000 26 970 000 000 55 3 950 000 3 160 000 000 88 710 000 4 680 000 000 56 3 400 000 40 000 000 000 89 350 000 12 600 000 000 57 3 000 000 690 000 000 90 20000 3 890 000 000 58 2 960 000 62 060 000 000 91 650 000 18 920 000 000 59 2 460 000 47 000 000 000 92 10000 200 000 000 60 2 010 000 9 470 000 000 93 1 500 000 19 070 000 000 61 1 990 000 7 600 000 000 94 220 000 3 460 000 000 62 1 820 000 650 000 000 95 40000 130 000 000 63 1 000 000 5270-000000 96 900 000 26 240 000 000 64 910 000 9 400 000 000 97 510 000 5080000000 65 800 000 110000000 98 170 000 2 080 000 000 66 620 000 43 000 000 000 99 10000 190 000 000 67 510 000 4 300 000 000 100 130 000 1 580 000 000 68 340 000 2 130 000 000 101 11500000 65 000 000 000 69 320 000 11 470 000 000 102 2 060 000 21 660 000 000 70 230 000 5 270 000 000 103 60000 650 000 000 71 160 000 3 070 000 000 104 420 000 16 400 000 000 72 70000 920 000 000 105 2 000 000 40 330 000 000 73 70 000 250 000 000 106 40000 270 000 000 1918] GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 233 can is emptied and washed, the amount of the milk still adhering to the walls of the can is extremely small.- That the milk held by a can previous to washing was not the prin- cipal source of the bacteria in the washed cans in cases where the num- ber of bacteria was large, may be shown by calculating the amount of the milk that would have been necessary to have supplied the num- ber of bacteria found in the washed cans. Cans 65 and 66 may be taken for this calculation. These two cans were washed in succession, within one minute of each other, in the same wash water. The germ content of the milk held by Can 65 w r as 800,000 bacteria per cubic centimeter, and the number of bacteria in this can after it was washed was 110,000,000. it would have required 137 cc. of the milk to have supplied the number of bacteria found in the can after it was washed. The germ content of the milk in Can 66 was 620,000 bacteria per cubic centimeter, and after the can was washed the number of bacteria found in it was 43,000,000,000. In this case it would have required 69,355 cc. (about 18 gallons) of the milk to have supplied this number of bacteria. It is seen from this experiment, therefore, that in dairies which receive milk with high germ content, the cans after being washed, and if not steamed, will have correspondingly large numbers of bacteria. On the other hand, the large numbers of bacteria in some cans after they are washed in the same dairy and in the same lot of wash water, must have some source other than the milk. Wash Water as a Source of Bacteria When milk is poured from a can, a small amount of it always ad- heres to the inner walls of the can. In the process of washing, these traces of milk are transferred to the wash water. It is evident that the germ content of the wash water may become very high if the milk was heavily seeded with bacteria, if the cans are dirty, or if a large number of cans are washed in the same lot of wash water. This ex- periment was therefore undertaken to determine the influence* of the wash water on the number of bacteria in the washed cans. All the cans reported in Table 8 were washed in one lot of wash water, and the same was true of those listed in Table 9. In Tables 10 and 11 a fresh lot of water was used for every set of cans, each set including from five to nine cans. In Table 8 the wash water contained one percent of sodium-car- bonate washing powder. In Table 9 the wash water contained no washing powder of any kind. In Table }0 each set of cans was washed first in one-percent washing-powder solution and, without using these cans for milk after this washing, they were washed again thirty min- utes later but only in plain water. In Table 11 the cans were treated exactly as in Table 10 except that the first washing was done in plain 234 BULLETIN No. 204 [February, water and the second washing in one-percent solution of washing powder. In Tables 8 and 9 the samples for bacteriological study were taken from the milk of each can just before the cans were emptied and washed. The samples from the wash water were taken from the vat : first, at the beginning of washing ; second, at certain intervals during the washing; and third, after all the cans were washed. In Tables 10 and 11, the milk samples were omitted, and the samples from the wash water in the vat were taken at the beginning and at the end of the washing of each set of cans. TABLE 8. GERM CONTENT OF MILK, OP WASH WATER, AND OP WASHED CANS (Cans washed in 25 gallons of water, with washing powder: Dairy B) No. of can Germ content of milk in cans, per ce. Bacteria removed from washed cans by one liter of rinse water Germ content of wash water, per cc. Before washing 100 000 1 2210000 1 690 000 000 2 300 000 4 440 000 000 3 5 520 000 30 400 000 000 4 350 000 18 650 000 000 5 10 830 000 5 670 000 000 6 14 500 000 8 400 000 000 7 2 750 000 70 660 000 000 8 1 390 000 104 330 000 000 9 290 000 21 800 000 000 10 9 500 000 720 000 000 11 10000 140 000 000 12 550 000 1 200 000 000 After 12 cans were washed 3 210 000 13 1 970 000 26 970 000 000 14 710 000 4 680 000 000 15 350 000 12 000 000 000 16 20000 3 890 000 000 17 650 000 18 920 000 000 18 10000 200 000 000 19 1 500 000 19 070 000 000 20 220 000 3 460 000 000 21* 40000 130 000 000 22 900 000 26 240 000 000 After 22 cans were washed 3 420 000 23 510 000 5 080 000 000 24 170 000 2 080 000 000 25 10000 190 000 000 26 130 000 1 580 000 000 27 11500000 65000000000 - 28 2 060 000 21 660 000 000 29 60000 650 000 000 30 420 000 16 400 000 000 31 2 000 000 40 330 OCO 000 32 40 000 270 000 000 After 32 cans were washed 5 100 000 1918} GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 235 After each can was washed it was allowed to stand twenty to thirty minutes; then one liter of sterile water was poured in and after thoro shaking, the germ content of this water was determined. In Tables 10 and 11 each can was washed twice in succession and the number of bacteria determined after each washing. All the cans in Tables 8 and 9, those in Table 10 numbering 21 to 43, and those in Table 11 numbering 27 to 44 came from Dairy B. The remaining cans in Tables 10 and 11 came from Dairy A. For the purpose of this experiment, however, the usual methods of wash- ing followed in these dairies were discarded and the cans in both dairies were washed "in the same way. About 25 gallons of warm water was run into the vat, and when washing powder was used, one percent of it was added to the water. Each can was placed in the water, scrubbed with a brush, and then inverted on a rack for about six seconds to drain. None of the cans in either dairy were rinsed with plain water after being washed. The germ content of the water supply in these dairies varied from 100 to 2,000 bacteria per cubic centimeter. It will be noticed from the above tables that when the water was run into the vat preparatory to being used for washing the cans, its germ content invariably in- creased. For example, in Table 8 before any cans were washed in the water the germ content was 100,000 bacteria per cubic centimeter. This increase was -apparently due to the bacteria present on the inner surface of the vat. TABLE 9. GERM CONTENT OF MILK, OF WASH WATER, AND OF WASHED CANS (Cans washed in 25 gallons of water, without washing powder: Dairy B) No. of can Germ content of milk in cans, per cc. Bacteria removed from washed cans by one liter of rinse water Germ content of wash water, per cc. Before any cans were washed 155 000 33 34 35 36 37 38 39 40 41 3 060 000 520 000 130 000 1 390 000 1 870 000 105 000 000 640 000 11 600 000 940 000 480 000 000 1 900 000 000 1 180 000 000 170 000 000 8 750 000 000 10 970 000 000 820 000 000 710 000 000 50 000 000 After 9 cans were washed 412 000 42 43 44 45 46 47 80000 80000 900 000 830 000 50000 6 300 000 720 000 000 490 00 000 1 170 000 000 . 10000000 280 000 000 14 690 000 000 After 15 cans were washed 457 000 236 BULLETIN No. 204 [February, TABLE 10. GERM CONTENT OF WASH WATER AND OF CANS WASHED TWICE IN SUCCESSION; FIRST IN WASHING-POWDER SOLUTION, THEN IN PLAIN WATER (New lot of 25 gallons of water used for every 5 to 9 cans) No. of can First washing washing powder Second washing plain water Bacteria removed from washed cans by one liter of rinse water Germ content of wash water, per ee. Bacteria removed from washed cans by one liter of rinse water Germ content of wash water, per cc. Dairy A Before washing 500 15400 1 2 3 4 5 7 000 000 24 000 000 17 000 000 1 000 000 3 000 000 500 000 400 000 100000 100 000 After 5 cans were washed 14 200 44 400 Before washing 28000 5600' 6 7 8 9 10 11 12 13 14 2 000 000 3 000 000 3 000 000 2 000 000 2 000 000 2 000 000 2 000 000 47 000 000 2 000 000 - 400 000 400 000 300 000 900 000 600 000 500 000 900 000 10 600 000 600 000 After 9 cans were washed 88 000 28 000 Before washing 21 800 7 500 15 16 17 18 19 20 500 000 700 000 600 000 700 000 1 600 000 700 000 490 000 600 000 900 000 410 000 640 000 620 000 After 6 cans were washed 40 000 47 000 Dairy B Before washing 28 000 17 000 21 22 23 24 25 190 000 000 100 000 000 3 190 000 000 10 400 000 000 240 000 000 30 900 000 20 100 000 723 000 000 787 000 000 14 600 000 After 5 cans were washed 20 000 000 1 400 000 Before washing 30000 7000 26 27 28 29 30 10 000 000 60 000 000 60 000 000 160 000 000 1 450 000 000 100 000 2 600 000 2 300 000 3 800 000 30 800 000 After 5 cans were washed 670 000 110 000 1918] GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 237 TABLE 10. Concluded No. of can First washing washing powder Second washing plain water Bacteria removed from washed cans by one liter of rinse water Germ content of wash water, per cc. Bacteria removed from washed cans by one liter of rinse water Germ content of wash water, per cc. Before washing 20500 5500 31 32 33 34 35 58 000 0-00 1 023 000 000 777 000 000 98 000 000 28 000 000 6 400 000 260 000 000 97 000 000 25 000 000 2 400 000 After 5 cans were washed 400 000 140 000 Before washing 19 000 18 200 36 37 38 39 40 41 42 43 40 000 000 3 000 000 5 700 000 000 753 000 000 194 000 000 1 153 000 000 4 400 000 000 173 000 000 17 600 000 1 000 000 2 830 000 000 96 600 000 11 000 000 250 000 000 1 066 600 000 10 100 000 After 8 cans were washed 14 000 000 450 000 As the process of washing proceeded, the number of bacteria in the wash water always increased. The thirty-two cans recorded in Table 8 were washed in water containing one percent of washing powder. Before any cans were washed, the water had 100,000 bacteria per cubic centimeter. After 12 cans were washed, the germ content of the water increased to 3,210,000 bacteria; after 22 cans were washed it increased to 3,420,000; and after 32 cans were washed it became 5,100,000. The water in which the cans in Table 9 were washed contained no washing powder. Its initial germ content was 155,000 bacteria per cubic centimeter, and after 15 cans were washed in it, its germ content increased to 457,000 bacteria. Similar results were obtained in Tables 10 and 11, where a new lot of wash water was prepared for every five to nine cans. In one case the initial germ content of the wash water was 28,000 bacteria per cubic centimeter, and after 5 cans were washed, its germ content increased to 20,000,000 bacteria. The number of bacteria added to the cans by the wash water de- pends naturally on the germ content of the water and also on the amount of the water left in the cans. Several trials on this point demonstrated that from 10 to 25 cc. of water adhere to the inner surface of a can. 238 BULLETIN No. 204 [February, TABLE 11. GERM CONTENT OF WASH WATER, AND OP CANS WASHED TWICE IN SUCCESSION ; FIRST IN PLAIN WATER, THEN IN WASHING-POWDER SOLUTION (New lot of 25 gallons of water used for every 5 to 9 cans) No. of can First washing plain water Second washing washing powder Bacteria removed from washed cans by one liter of rinse water Germ content of wash water, per cc. Bacteria removed from washed cans by one liter of rinse water Germ content of wash water, per cc. Dairy A Before washing 400 13 200 1 2 3 4 5 340 000 000 1 000 000 2 000 000 277 ooo ooo 4 000 000 \ 100 000 7 000 000 4 000 000 After 5 cans were washed 11 800 47 600 Before washing 500 15 400 6 7 8 9 10 7 000 000 24 000 000 17000000 1 000 000 3 000 000 500 000 400 000 100 000 100 000 After 5 cans were washed 14 200 44 400 Before washing 1 400 3 300 11 12 13 14 15 16 17 18 19 1 000 000 7 000 000 14 000 000 3 000 000 2 000 000 1 000 000 2 000 000 5 000 000 232 000 000 800 000 7 000 000 300 000 800 000 700 000 1 0-00 000 1 700 000 1 300 000 17 900 000 After 9 cans were washed 200 000 94 000 Before washing 12 900 6 100 20 21 22 23 24 25 26 9 000 000 1 000 000 1 100 000 1 200 000 1 300 000 400 000 1 200 000 620 000 580 000 620 000 770 000 700 000 790 000 830 000 After 7 cans were washed 09 000 1018] GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 239 TABLE 11. Concluded No. of can First washing plain water Second washing washing powder Bacteria removed from washed cans by one liter of rinse water Germ content of wash water, per ce. Bacteria removed from washed cans by one liter of rinse water Germ content of wash water, per ce. Dairy B Before washing 200 27 3 350 000 000 115 200 000 28 970 000 000 23 700 000 29 3 630 000 000 143 300 000 30 140 000 000 9 600 000 31 450 000 000 500 000 After 5 cans were washed 4 800 000 510 000 Before washing 1 400 28 000 32 1 084 000 000 783 000 000 33 11 000 '000 2 700 000 34 3 416 000 000 355 000 000 35 132 000 000 82 000 000 36 26 000 000 9 800 000 After 5 cans were washed 1 200 000 600 000 Before washing 107 000 37 37 000 000 82 700 000 38 55 000 000 66 000 000 39 184 000 000 64 700 000 40 748 000 000 123 300 000 41 33 000 000 10 300 000 42 563 000 000 100 300 000 43 25 000 000 22 000 000 44 47 000 000 14 800 000 After 8 cans were washed 14 400 000 450 000 'Cans 31 and 32 in Table 8 were washed in the same water within one minute of each other. In Can 31 the bacteria numbered 40,330,- 000,000 and in Can 32, 270,000,000. The germ content of the wash water at this point was 5,100,000 bacteria per cubic centimeter. If the number of bacteria in these two cans was due to the wash water alone, it would have required 53 cc. of the water to have sup- plied the number in Can 32, while in Can 31 it would have required 7,907 cc. of the water. Similar calculations for each can in these tables show that in some cans the relatively small numbers of bacteria correspond somewhat closely to the number of bacteria in the amount of the water that may adhere to them. However, in many of the cans the number is too large to be accounted for by the wash-water con- tamination alone. In addition, there appears to be no gradual in- crease in the germ content of the consecutively washed cans. This leads to the conclusion, therefore, that the exceptionally large numbers 240 BULLETIN No. 204 [February, of bacteria in the washed cans had some other source than the wash water. In 1889 Conn stated that ''bacteria gather upon the sides of the utensils and develop in the minute portions of milk, grease, and other matter from which it is difficult to free the vessels completely by washing." The data in this experiment support Conn's conclusion and further emphasize the striking capacity of the bacteria to mul- tiply in the extremely minute portions of the milk, fat, and other matter, and to adhere to the walls of the cans. The large numbers of bacteria found in cans may be accounted for on the ground that the cans are difficult to clean thoroly, and that in the traces of this dirt numerous bacteria are imbedded and then are loosened by the washing process and subsequently removed by rinsing. The purpose of this experiment was also to show the influence of the washing powder upon the germ content of the wash water and the washed cans. The cans listed in Table 8 were washed in water containing washing powder and those in Table 9 in plain water. Those shown in Tables 10 and 11 were washed twice in succession, half of them in washing-powder solution first and then in plain water, and half in plain water first and then in washing-powder solution. A perusal of these tables shows that the washing powder exerted no dis- cernable influence upon the germ content of the wash water or of the washed cans. The germ content of the wash water increased during the washing process to about the same extent in the plain water and in the washing-powder solution, and many of the cans in both cases had extremely large numbers of bacteria'. It is customary in some dairies to wash a large number of uten- sils in the same lot of wash water, and then not to rinse them suffi- ciently with clean water or not to rinse them at all. Such practice results in seeding the wash water with large numbers of bacteria which were present in the dirt and in the milk that adhere to the walls of the utensils. When utensils are washed in such a manner, some may contain a larger number of bacteria after they are washed than they contained before they were washed. Naturally the object of the washing process is to remove the dirt and the milk residues from the can, and the completeness with which it accomplishes this result is the true measure of its success. A re- duction of the germ life in the can is ordinarily accomplished at the same time, but this reduction cannot be carried to satisfactory limits by the washing process without an undue expense for water, heat, and washing powder. The destruction of the germ life in the cans is ordinarily accomplished more economically and more completely by the direct application of steam. 1918] GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 241 BACTERIA FOUND IN BOTTLES FRESHLY WASHED AND IN BOTTLES STANDING TWENTY-FOUR HOURS ^ The washing of milk bottles is in a measure comparable to that of cans. Like cans, the bottles are washed in the same water in large numbers. They are returned to the dairy at times in dirty condition and frequently contain traces of milk with high germ content: In the dairy in which this experiment was conducted, it was the custom to wash from 150 to 200 bottles in a vat containing about 60 gallons of warm water to which was added 5 pounds of sodium-car- bonate washing powder. The bottles were scrubbed with a steam- driven brush, and then rinsed in another vat containing about 60 gallons of tap water; they were not steamed. For the purpose of this experiment two sets of the washed bottles, nine to fourteen in each set, were selected from each of fourteen different lots for study. In order to obtain two comparable sets of bottles, selection was made in the following manner: The first two bottles washed were taken, then the eleventh and twelfth, then the twenty -first and twenty- second, and so on until all the bottles were washed. Those having odd numbers constituted the first set and those with even numbers the second set. The bottles in the first set were examined immediately after being washed and those in the second set after they had been kept inverted twenty-four hours on a wire rack. The examination consisted in rinsing each bottle with 100 cc. of sterile water and de- termining the number of bacteria in the water. The results of the examination of 308 bottles are given in Table 12. The number of bacteria found in these bottles was variable and in some cases large. Among the bottles examined immediately after washing 25, or 16.2 percent, had more than one million bacteria, and 129, or 83.8 percent, had less than one million. The largest number of bacteria found in any one bottle was 40,660,000, and the smallest was 20,000. The bottles that were held twenty-four hours after they were washed were found to be dry and free from bad odors. Eighty-four of these, or 54.5 percent, had more than one million bacteria, and 70, or 45.5 percent, had less than one million. The largest number of bacteria found was 231,700,000, and the smallest number was 3,000. ' It will be observed that some of the bottles examined immediately after they were washed had a larger number of bacteria than some of the bottles held twenty-four hours. On the average, however, there was a decided increase in the number of bacteria in the bottles which were held twenty-four hours. This is brought out more clearly by calculating the average number of bacteria per bottle on each of the different days/- These averages are given in Table 13. The averages in Table 13 show that, in all cases, the set of bottles held twenty-four hours averaged more bacteria than the corresponding 242 BULLETIN No. 204 [February, TABLE 12. NUMBER OF BACTERIA IN BOTTLES FRESHLY WASHED. AND TWENTY-FOUR HOURS LATER: DAIRY A (As determined by rinsing each bottle with 100 cc. of sterile water) * Total number of bacteria in bottles Total number of bacteria in bottles No. of Freshly No. of 24 hours after No. of Freshly No. of 24 hours after bottle washed bottk washing bottle washed bottle washing June 20 June 20-21 June 21 June 21-22 1 3 800 000 2 47 000 000 25 110 000 26 3 040 000 3 6 000 000 4 68 300 000 27 110 000 28 36 500 000 5 5 200 00 6 120 000 000 29 140 000 30 61 330 000 7 4 700 000 8 123 000 000 31 110 000 32 11 800 000 9 4 300 000 10 107000000 33 90000 34 48 670 000 11 4 500 000 12 15 500 000 35 - 120000 36 22330000 13 15 000 000 14 36 000 000 37 110 000 38 29 330 000 15 7 900 000 16 231 700 000 39 490 000 40 36 330 000 17 6 100 000 18 18 700 000 41 140 000 42 68 000 000 19 11 300 000 20 64 600 000 43 40 660 000 44 72 330 000 21 8 000 000 22 27 700 000 23 6 600 000 24 163 000 000 June 22 June 22-23 , June 23 June 23-24 45 2 950 000 46 4 700 000 63 30000 64 2 290 000 47 100 000 48 100 000 65 2 730 000 66 1 280 000 49 340 000 50 5 130 000 67 40000 68 6 030 000 51 520 000 52 15 430 000 69 200 000 70 15 000 000 53 110 000 54 6 570 000 71 70000 72 8 570 000 55 270 000 56 20 670 000 73 120 000 .74 9 870 000 57 850 000 58 5 400 000 75 190 000 76 34 000 000 59 210 000 60 910 000 77 80000 78 1 830 000 61 780 000 62 180 000 79 100 000 80 3 190 000 June 26 June 26-27 June 27 June 27-28 81 630 000 82 360 000 101 43000 102 30000 83 410 000 84 30 500 000 103 315 000 104 2 700 000 85 320 000 86 430 000 105 83000 106 480 000 87 340 000 88 300 000 107 68000 108 210 000 89 760 000 90 30000 109 40000 110 10000 91 400 000 92 120 000 111 335 000 112 470 000 93 230 000 94 170 000 113 54000 114 160 000 95 590 000 96 140 000 115 48000 116 10000 97 250 000 98 350 000 117 303 000 118 1 490 000 99 220 000 100 120 000 119 71000 120 2 020 000 June 28 June 28-29 June 30 June 30 July 1 121 62000 122 370 000 139 305 000 140 830 000 123 295 000 124 80000 141 243 000 142 1 920 000 125 175 000 126 140 000 143 279 000 144 10000 127 901 000 128 230 000 145 30000 146 750 000 129 170 000 130 100 000 147 600 000 148 2 070 000 131 220 000 132 15 160 000 149 61000 150 630 000 133 333 000 134 80000 151 2 430 000 152 470 000 135 5 733 000 136 1 500 000 153 93 000- 154 250 000 137 1 130 000 138 90000 155 41000 156 320 000 157 61000 158 260 000 ISIS] GERM CONTEXT OF MILK AS INFLUENCED BY UTENSILS 243 TABLE 12. Concluded Total number of bacteria in bottles- Total number of bacteria in bottles No, of Freshly No. of 24 hours after No. of Freshly No. of 24 hours after bottle washed bottle washing bottle washed bottle washing Sept. 25, Sept. 25-26, Sept. 25, Sept. 25-26, a. m. a. m. p. m. p. m. 159 450 000 160 90000 183 43000 184 13 330 000 161 36000 162 3000 185 46000 186 1 926 000 163 40000 164 3 090 000 187 66000 188 2 826 000 165 26000 166 853 000 189 36000 190 3 026 000 167 50000 168 3000 191 66000 192 310 000 169 50000 170 250 000 193 43000 194 310 000 171 63000 172 43000 195 33000 196 930 000 173 36000 174 660 000 197 50000 198 350 000 175 40000 176 76000 199 30 000 200 630 000 177 . 53000 178 396 000 201 740 000 202 316 000 179 66000 180 1 300 000 203 66000 204 2 773 000 181 20000 182 206 000 205 80000 206 150 000 Sept. 27, Sept, 27-28, Sept. 27, Sept. 37-28, a. m. a. m. p. m. p. m. 207 83000 208 4 880 000 231 340 000 232 4 560 000 209 593 000 210 4 800 000 233 350 000 234 3 746 000 211 90000 212 110 000 235 540 000 236 5 300 000 213 276 000 214 4 226 000 237 396 000 238 11 400 000 215 276 000 216 4073000 239 1 553 000 240 6 933 000 217 283 000 218 8 600 000 241 300 000 242 1 753 000 219 110 000 220 313 000 243 740 000 244 3 700 000 221 100 000 222 320 000 245 540 000 246 2 950 000 223 163 000 224 13000 247 370 000 248 13 660 000 225 2 493 000 226 3 396 000 249 660 000 250 10 300 000 227 363 000 228 6000 251 1 043 000 252 1 336 000 229 570 000 230 660 000 253 1 090 000 254 12 330 000 Sept. 2?, Sept. 29-30, Oct. 2, p. m. Oct. 2-3, p.m. a. m. a. m. 255 6 986 000 256 6 400 000 285 73000 286 50000 257 280 000 258 9 530 000 287 57000 288 10000 259 3 160 000 260 2 670 000 289 99000 290 60000 261 450 000 262 2 100 000 291 77000 292 10 720 000 263 340 000 264 6 020 000 293 165000 294 80000 265 436 000 266 3 995 000 295 237 000 296 30 00.0 267 230 000 268 2 600 000 297 63000 298 110 000 269 513 000 270 4 606 000 299 46000 300 10000 271 253 000 272 3 853 000 301 44000 302 2 020 000 273 8 700 000 274 4 253 000 303 56000 304 270 000 275 350 000 276 3366000 305 74000 306 260 000 277 286 000 278 1 963 000 307 64000 308 110 000 279 400 000 280 60000 281 386 000 282 3000 283 296 000 284 26000 244 BULLETIN No. 204 [February, set of the same day examined immediately after the washing. The average number of bacteria in all the 154 bottles examined immediately after the washing was 1,271,950 per bottle, and in those held twenty- four hours it was 12,283,490 per bottle. One quart is approximately 950 cubic centimeters ; so that if these bottles had been filled with milk, the germ content of the milk would have been increased, on the average, by 1,339 bacteria per cubic centi- meter by the freshly washed bottles and 12,930 bacteria per cubic centimeter by the bottles held twenty-four hours after the washing. From these results it is evident that bottles washed but not steamed may have an appreciable effect upon the germ content of milk, espe- cially when they are held for some hours before being filled. TABLE 13. AVERAGE NUMBER OF BACTERIA IN WASHED BOTTLES Date, Number of Bottles freshly Bottles held 24 hours 1916 bottles washed after washing June 20 12 6 950 000 85 200 000 21 10 4 208 000 38 966 000 22 9 681 000 6 565 000 23 9 395 000 9 115 000 26 10 415 000 3 252 000 27 10 136 000 758 000 28 9 1 002 000 1 970 000 30- 10 414 000 751000 Sept. 25 a.m. 12 78 OOO' 581000 25 p.m. 12 108 000 2 240 000 27 a.m. 12 450 000 2 616 000 27 p.m. 12 660 000 6 497 000 29 a.m. 15 1 538 000 3 429 000 Oct. 2. p.m. 12 879 000 1 144 000 Average number of bacteria in 154 bottles. . 1 271 950 12283490 1918} GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 245 PART II. INFLUENCE SHOWN BY EXAMINATION OF THE MILK The four experiments reported in this part were designed to ascer- tain the influence of the various unsteamed utensils upon the germ content of milk, in actual dairy operations. This influence was measured by the difference in the germ content of milk handled in steamed and in unsteamed utensils. The utensils were washed as described on page 219. The steaming consisted in holding the utensils in a chamber filled with flowing steam, for about an hour, with the exception that some of the pails and cans were held over a jet of steam for two to three minutes. The thoroness of the steaming of the utensils was always tested bacteriolog- ically and found to be satisfactory. COLLECTIVE INFLUENCE OF UTENSILS AT THE BARN This experiment was designed to measure the collective influence on the germ content of milk of unsteamed pails, strainers, and cans used at three dairy barns. In each barn the milk was drawn into small-topped pails and strained thru a combination cloth and wire strainer into eight-gallon cans. After each milking, the utensils were washed in water containing washing powder, rinsed in a vat of tap water, and placed on a rack. At each milking a new strainer cloth was used. The utensils were used, as a rule, in from six to twelve hours after being washed, altho in a few cases cans were held twenty- four to thirty-six hours. Normally, the utensils were steamed after being washed at these dairy farms ; but in order to bring out the influence of unsteamed uten- sils, the steaming was omitted on some days. The samples of milk were removed from the cans for bacteriological examination within one hour after milking, both when the utensils had been steamed and when they had been left unsteamed. The results of bacteriological examination are given in Tables 14 to 19. These tables present a striking contrast between the germ content of milk handled in steamed utensils and that handled in unsteamed utensils. When the pails, the strainers, and the cans were steamed, only 4 cans of milk out of 34 in Barn I, and 3 out of 35 in Barn II had a germ content above 10,000 bacteria per cubic centimeter. The average germ content for all the milk handled in steamed utensils was 4,865 bacteria per cubic centimeter in Barn I and 3,157 in Barn II. The results from Barn III were somewhat higher, the average germ content being 12,400 per cubic centimeter for steamed utensils. On the other hand, when the utensils were not steamed, the germ content of the milk became higher and more variable. Of the 117 cans 246 BULLETIN No. 204 [February, of milk from the three barns, 7 had more than one million bacteria per cubic centimeter, 81 had above 100,000, and only 2 had less than 10,000. The highest germ content in a single can was 2,623,100 and the lowest was 7,100. The average germ content for all the milk handled in unsteamed utensils was 311,000 for Barn I, 326,880 for Barn II, and 218,930 for Barn III. The bacteria that were found in the milk in these cans were con- tributed by all the sources of contamination to which the milk was exposed on its way from the udder to the cans. The difference between the germ content of the milk handled in the steamed utensils and that TABLE 14. GERM CONTENT CF MILK HANDLED IN. STEAMED PAILS, STRAINERS, AND CANS: BARN I No. of can Oct. 3, 1914, a.m. Oct. 4, a.m. May 12, 1915, a.m. May 13, a.m. May 21, a.m. May 22, a.m. May 25, a.m. Number of bacteria per cc. of milk in cans 1 2 3 4 5 6 7 1904 2486 3280 2502 1690 1267 6805 5727 5542 7290 10720 3617 3482 3032 1660 3500 15522 6200 4950 8885 12075 1170 5285 3952 4997 4652 2555 826 2600 3592 10510 2712 5837 4600 TABLE 15. GERM CONTENT OF MILK HANDLED IN UNSTEAMED PAILS, STRAINERS, AND CANS: BARN I No. of can May 3, 1915, p.m. May 4, a.m. May 5, p.m. May 6, a.m. May 6, p.m. May 7, a.m. Number of bacteria per cc. of milk in cans 1 2 3 4 5 6 78700 38400 4560-0 130 500 7100 28800 624 500 887 500 763 100 57100 18200 2 623 100 9200 108 000 779 000 120 000 39100 23200 30200 31200 90400 TABLE 16. GERM CONTENT CF MILK HANDLED IN STEAMED PAILS, STRAINERS, AND CANS: BARN II No. of Oct. 3, 1914, a.m. May 12, 1915, a.m. May 12, p.m. May 13, a.m. June 1, p.m. June 3, p.m. can Number of 1 Bacteria per cc. of milk in cans I o 4 5 8 7 785 610 837 235 770 5960 1500 2187 19400 ' 886 850 1985 1616 1722 1977 4027 2 456 1605 1820 2077 1040 6015 2816 6507 1297 11837 4515 4692 1237 942 785 1205 1777 10667 8 1837 1918] GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 247 of the milk handled in the unsteamed utensils gives approximately the number of bacteria contributed by the unstcamed pails, strainers, and cans. From the foregoing figures this difference is seen to be 306,135 bacteria per cubic centimeter for the milk handled in Barn I ; 323,723 bacteria per cubic centimeter for the milk handled in Barn II ; and 206,530 bacteria per cubic centimeter for the milk handled in Barn III. In other words, the unsteamed pails, strainers, and cans added to the milk 64 times as many bacteria as all the other sources of con- tamination at Barn I, 103 times as many in Barn II, and 18 times as many in Barn III. TABLE 17. GERM CONTENT OF MILK HANDLED IN UNSTEAMED PAILS, STRAINERS, AND CANS: BARN II No. of April 27, 1915 a.m. April 28, p.m. April 29, p.m. May 3, a.m. May 3, p.m. May 4, a.m. can. Number o; bacteria pe ;r cc. of mi] k in cans 1 2 3 4 5 6 7 212 000 310 000 97300 123 500 120 000 124 700 133 700 89200 363 500 275 800 111 200 123 600 422 500 485 000 18400 52800 21500 32800 35 100 62 300 73500 828 000 852 000 410 500 1 124 000 369 000 703 000 118 700 77100 83900 195 800 61500 111 100 143 200 426 200 575 000 254 700 237 000 554 000 445 000 May 4, p.m. May 5, a.m. May 5, p.m. May 6, a.m. May 6, p.m. May 7, a.m. j. 2 3 4 5 6 75000 65300 114 100 158 300 62500 348 O'OO 538 000 172 200 762 500 630 500 139 000 208 500 127 600 399 700 170 200 223 700 434 500 1 135 000 1 347 200 544 600 356 500 1 053 700 392 500 127 400 159 500 298 400 221 100 107 500 286 400 690 000 393 700 127 700 127 900 1 520 000 374 000 7 271500 195 700 279 000 TABLE 18. GERM CONTENT OF MILK HANDLED IN STEAMED PAILS, STRAINERS, AND CANS: BARN III No. of can May 11, 1915 p.m. May 12, a.m. May 12, p.m. May 13, a.m. June 1, p.m. June 3, p.m. Number of bacteria per cc. of milk in cans 1 2 8295 7980 41150 10737 9652 3782 17 405 4833 5442 13112 6027 20490 TABLE 19. GERM CONTENT OF MILK HANDLED IN UNSTEAMED PAILS, STRAINERS, AND CANS: BARN III No. of can May 3, 1915 a.m. May 3, p.m. May 4, a.m. May 4, p.m. May 5, a.m. May 5, p.m. May 6, a.m. May 6, p.m. May 7, a.m. Number of bacteria per cc. of milk in cans 1 2 130 000 25400 40000 37 200 39800 75400 51700 121 700 154 700 214 200 109 000 1 538 500 335 500 495 500 183 400 94100 210 500 84100 248 BULLETIN No. 204 [February, INFLUENCE OF UNSTEAMED BOTTLE FILLER UPON GERM CONTENT OF MILK The bottle filler used for this experiment was the "double-end, four-quart and five-pint filler" shown in Fig. 1. It consisted of a tank and nine valves, each valve having a stem, a sleeve, an air tube, a wire coil spring, and a rubber washer. In washing the bottle filler the valves were taken apart and placed inside the filler tank. The tank and all the parts were then scrubbed with a brush and washing powder and rinsed with a hose. After the bottler was cleaned in, this manner, it remained standing in the milk room about twenty hours before it was used again. When it was to be steamed, it was covered with a galvanized iron lid, the valve openings were stopped with corks, and the steam was allowed to flow into it for thirty minutes. The steaming was done about one hour before bottling, and its thoroness was always tested by a bac- teriological examination. The milk bottles were steamed in all cases. From 300 to 400 quarts of milk were pasteurized and bottled each day. The milk was pasteurized in a vat ; then cooled in the same vat by passing brine thru a coil revolving in the milk; and then it was bottled immediately. Samples of the milk were taken from the pas- teurizing vat just before bottling, and then during the process, from the first bottle filled, thru one of the four valves and then from every ninth bottle filled thru the same valve. Since there were four valves in the bottle filler, every ninth bottle filled thru one valve was actually every thirty-sixth bottle filled. Table 20 gives the germ content of the milk when the bottle filler was steamed, and Table 21 when it was washed but not steamed. The bottles in both cases were steamed before being used. TABLE 20. GERM CONTENT OF PASTEURIZED AND BOTTLED MILK WHEN BOTTLE FILLER AND BOTTLES WERE STEAMED: DAIRY A Samples of milk from: Jan. 4, 1916 Jan. 5 Jan. 6 Jan. 7 Jan. 8 | Average Number of bacteria per cc. of milk Pasteurizer 1832 1887 2782 2165 2257 2250 2 167 265 420 260 305 255 320 230 1497 1270 1310 1637 1287 . 2027 1 182 100 65 40 80 50 60 395 922 1432 1225 916 1090 832 1 180 923 1015 1123 1021 969 1098 1 031 1st bottle 36th 72d 108th 144th 180th Table 20 shows that when the bottle filler was steamed shortly before use, the germ content of the bottled milk was approximately the same as that in the pasteurizing vat. If any increase took place, it was not measurable. When, however, the bottle filler, which had GKRM CONTENT OF MILK AS INFLUENCED BY UTENSILS 249 PH P I *OOOOO,OOO|OOOO oooooooooo OOC^OOCQO5t~C.-^lOi IOJ(MT-(iHr-l O r-l rH r-t IOOOOOOOOOOO OOOOOO > O O C> O> CD O -O O O O O o O OOOOOOO < CO <>J rH rH & -a 250 BULLETIN No. 204 [February, stood for twenty hours after washing, was hot steamed, a conspicuous increase in the germ content of the bottled milk took place. Table 21 for instance, shows that on December 18 the germ content of the milk in the pasteurizing vat was but 60 bacteria per cubic centimeter while in the first bottle filled it was increased to 209,600 bacteria. The averages shown in the last column in Table 21 present a striking illustration of the effect of the unsteamed bottle filler on the germ content of the milk passed thru it. The average germ content FIG. 1. BOTTLE FILLER USED IN THE EXPERIMENT of the milk before bottling was 84 bacteria per cubic centimeter ; of the first bottle filled it was 96,900 ; and of the last bottle, 2,288. There was evidently a gradual washing out of the bacteria of the bottle filler by the milk' passed thru it, the greatest proportion being removed by the first milk. However, the effect of the unsteamed bottler was evi- dent even in the last bottle filled. COLLECTIVE INFLUENCE) OF UTENSILS AT THE BARN AND AT THE DAIRY In the barn and in Dairy A, in which this study was conducted, about 100 to 200 quarts of milk came into contact with the utensils during the process of milking. The utensils used comprized five pails, two strainers, two weighing pails, one sanitary tube fifteen feet long, 1918} GERM CONTENT OF MILK AS INFLUENCED BY UTENSILS 251 (M cq b- cq ^ b- CO O OS OS CO rH CO cq ic cq os ic co i * * Tt< cq O .. .. .. 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