CALIFORNIA AGRICULTURAL EXTENSION SERVICE CIRCULAR 69 NOVEMBER, 1932 SANITARY CARE, OPERATION, AND INSTALLATION OF MILKING MACHINES J. L. HENDERSON, C. L. ROADHOUSE, AND A. FOLGER Cooperative Extension work in Agriculture and Home Economics, College of Agriculture, University of California, and United States Department of Agriculture cooperating. Distributed in furtherance of the Acts of Congress of May 8, and June 30, 1914. B. H. Crocheron, Director, California Agricultural Extension Service. THE COLLEGE OF AGRICULTURE UNIVERSITY OF CALIFORNIA BERKELEY, CALIFORNIA DIRECTIONS FOR CLEANING AND STERILIZING MILKING MACHINES (1) Draw iy 2 gallons of cold water through each milking ma- chine unit in the barn immediately after milking the last cow. Move the teat cups in and out of the water several times to break the vacuum and secure an air-brush effect. (2) Draw V/ 2 gallons of hot water (165°-170° F) through each unit. Washing powder may be added to this water. (3) Disconnect the rubbers from the claw and head of the machine and wash them in warm water containing wash- ing powder, using brushes or ramrods of appropriate size for each size of tube. Repeat this procedure after each milking. (4) Rinse again in warm water to remove the washing so- lution. (5) Sterilize by heating in water to 185° F; let stand for 20 minutes, without addition of more heat. Drain the water from the container and leave it covered until the next milking. If the tank is not used, the rubbers may be assembled on a claw and hung in the milk house or refrig- erator away from flies and dust. (6) Thoroughly wash and brush the metal parts of the ma- chine after each milking and sterilize them in steam in a farm sterilizer. (7) Regularly once a week, rinse the pipe lines and sterilize with steam if possible. SANITARY CARE, OPERATION, AND INSTALLATION OF MILKING MACHINES J. L. HENDERSON,i C. L. ROADHOUSE^ and A,. FOLGER3 INTRODUCTION A survey of the number of milking machines used by members of cow- testing associations in the leading dairy counties of California made early in 1932 shows that 42 per cent of these dairy farmers are using milking machines. This wide use of machines, coupled with a lack of uniformity in their sanitary care, as found on many dairy farms, makes it seem desirable to have a standard procedure for their care and oper- ation. The recommendations made in this circular are based largely on studies conducted for a period of two years, during which methods of cleaning, sterilization, operation, and installation of milking ma- chines were investigated. The procedure adopted conforms to the provisions of the California State Dairy Laws. Many years of experience have shown that milk drawn with the aid of machines may be produced as low in bacterial content as that pro- duced with the most scrupulous care in hand milking, provided that proper methods of cleaning, sterilization, and operation are carried out. Few, however, have succeeded in producing milk of low bacterial count 4 throughout a long period with milking machines, without occasional irregularities in the bacterial content. The cause has usually been im- proper cleaning, sterilizing, and operating of the machines rather than any fault of the machine. One common objection to the use of milking machines has been the belief that the udders of the cows were ruined and that milk production was decreased. In recent years numerous workers have reported that modern types of milking machines, when properly operated, have no ill effects on the cow's udder or on milk production. i Research Assistant in Dairy Industry. 2 Professor of Dairy Industry and Dairy Technologist in the Experiment Station. 3 Supervisor of Official Advanced Registry Tests. * The term ' ' bacterial count ' ' refers to the number of bacteria found in a cubic centimeter of milk, which is about 16 drops. California Agricultural Extension Service t ClR - 69 CLEANING MILKING MACHINES Immediately after milking, the surfaces of the rubber parts of the machine should be rinsed before the milk solids have dried upon them and become difficult to remove. Cold or lukewarm water should be used for this first rinse because hot water would cause the milk proteins to adhere to the surfaces of the rubbers and render proper cleaning difficult. The best practice is to make this cold rinse a part of the milking procedure and to draw IV2 to 2 gallons of clean cold water through the machine by vacuum imme- diately after the last cow has been milked. An air-brush effect can be secured by alternately lifting the cups out of the water and then immersing them in a pail of water while the vacuum remains connected. Machines that do not have long milk tubes and claws cannot be so rinsed; and it is recommended, therefore, that immediately after the last cow has been milked a machine of this type be taken to the milk house, where the rubbers should be disconnected from the pail and placed in a tank or pail of cold water (fig. 3) . Hot water at a temperature between 165° and 170° F should next be drawn through the machine by vacuum. This second rinse of IV2 to 2 gallons of water is used to remove the remaining milk. The water should be drawn through the machine by continuous rather than inter- mittent suction. If no vacuum connection is available in the milk house, a vacuum may be drawn on the pail in the barn after the cold water rinse, and the pail then removed to the milk house, where hot water may be drawn through the rubbers by the vacuum remaining in the pail (%. 4). The hot water rinse is very important in cleaning milking machines because it removes most of the adhering milk fat. At the temperature used for sterilization, rubber quickly absorbs any fatty substance, and its tensile strength is thereby reduced. In consequence, as two investi- gators 5 ' 6 report, the life of the rubber parts is materially shortened when the hot rinse is not used. After the milk has been thus removed from the surfaces, the re- mainder of the cleaning process may be delayed without detriment. 5 Burgwald, L. H. Cleaning milking machines. U. S. Dept. Agr. Farmers' Bui. 1315:1-16. 1923. 6 Lockhead, A. J., and C. K. Johns. Bacterial investigations of milking ma- chines. Canada Dept. Agr. Bui. 127. New series p. 1-37. 1929. 1932 J Care of Milking Machines 5 Brushing the rubber parts is the third step in the proper cleaning of milk machines. For this purpose, a two-compartment washing and rinsing tank is recommended, and warm water containing washing- powder should be used. With the claw- type machines, the short milk tubes and short air tubes should be disconnected from both the claw and the metal teat cups, and a brush passed through them after each milking. The teat cups and the long milk tubes should also always be cleaned with brushes of appropriate size. Metal cleaners for milk tubes, resembling ramrods with a bur at one end, may be used in place of brushes in cleaning the long and short milk tubes. The metal cleaners are especially useful if the brushes have been permitted to become worn or have not been kept in a sanitary condition. With some types of machines, the inflation rubbers should be removed from the metal casings after each milking ; with others this may be done once a week, when the insoluble material that may have accumulated around the ring may be removed and the inflation rubbers trimmed to the proper length, if necessary, and reversed in the metal casings. In any case, the insides of the inflation rubbers should be thoroughly brushed and washed after each milking and should then be rinsed in clean, warm water to remove the cleaning solution. The metal parts (i.e., the head, claw, and pail) must also be thoroughly washed and brushed after each milking (figs. 5, 6, and 7) . A uniform daily procedure in cleaning the milking machines will facilitate the work and insure a thorough cleaning. STERILIZATION OF MILKING-MACHINE RUBBERS Sterilization is the next and most important step in the procedure of producing milk of low bacterial count when milking machines are used. As a clean machine is not necessarily bacteria-free, sterilization is necessary to destroy the bacteria which are liable to be present in dairy equipment. The metal parts are easily sterilized by steaming them in a sterilizer or by immersing them in boiling water. Rubber tubes and inflation rubbers, however, will deteriorate rapidly when held at a high tempera- ture for a long time. ' ' Sterilization ' ' as usually applied to dairy equip- ment refers to the destruction, either by heat or by chemicals, of most of the bacteria present in the equipment after washing. Both heat and chemical sterilization have been investigated by the authors as to the effi- ciency and reliability of the two methods in destroying bacteria and the effect on the life (period of usefulness) of the rubbers. 6 California Agricultural Extension Service [ Ci R- 6 9 Heat sterilization was found to give consistently the lowest bacterial counts and to be the most reliable method of sterilizing milking-mauiine rubbers when the temperature and time of holding recommended in this circular were observed. The California State Dairy Law requires that all dairy apparatus be sterilized by heating to a temperature ^ ^ least 170° F and holding it at that temperature for a period of nc than 15 minutes. It was shown that heating the rubbers to a temperature of 185° F, holding them for 20 minutes in the heating tank without applying addi- tional heat, and then draining out the water, gave the lowest bactr^*ial counts and did not materially shorten the life of the rubbers as com- pared with heating at lower temperatures. This comparison was made by sterilizing the rubber tubes at 170° F for 20 minutes. In this latter method the application of heat had to be continued for 15 minutes to prevent the temperature from falling below the 170° F minimum re- quired by the California Dairy Law. The lower temperature of heat- ing is not so satisfactory because of the additional attention required to keep above the minimum requirement of the law, and the bacterial content of the rubbers was somewhat higher thereafter. The life of the inflation rubbers was 9 weeks with the lower temperature of heating, that of the short milk tubes, 19 weeks. When the rubber parts were heated to 170° F, held at that tempera- ture for 20 minutes, and left in the water to cool gradually between milkings, their bacterial content was considerably increased, the life of the inflation rubbers on the average was decreased 1 week (i.e., from 9 to 8 weeks), and that of the short milk tubes was decreased 9 weeks (i.e., from 19 to 10 weeks) . In addition, thermophilic bacteria developed in the water and caused objectionable additional contamination. The container in which the rubbers were heated (fig. 1) was a gal- vanized tank 50 inches long, 12 inches wide, and 12 inches high, fitted with a sloping tray which held the rubbers in a slanting position so that no air pockets would occur in the long milk tubes and which permitted them to drain out well when the water was removed from the tank. The water was heated by means of a steam pipe that ran the length of the tank and which was provided with numerous holes at regular intervals along its underside, thus assuring uniform heating of the water. After the water was drained out, the rubbers were left in the tank between milkings in order to protect them from flies and dust. When the rubbers are placed in an ordinary wash boiler or milking pail for sterilization, they may afterwards be hung in the refrigerator or in a cabinet to protect them from contamination. For successful heat sterilization, an 1932] Care of Milking Machines accurate thermometer must be used each time the water is heated. The rubbers should not be left in the water too long, or they will lose their elasticity. An accurate thermometer should be used to determine the tempera- tir ; of heating for each sterilization. In large dairies, a recording ther- nt iieter may be installed in the heating tank. This serves as a check upon the work of employees and should give more satisfactory results. Ghemical sterilization is not acceptable for the treatment of milking- machine parts or other dairy apparatus in California unless it is accom- panied by heat sterilization. Experience has shown, and the experiments Fig. 1. — Tank used for heat sterilization. 1, Galvanized iron tank 12x12x50 inches. 2, Corrugated iron tray used to hold rubber parts. The sloping surface pre- vents air pockets in the long tubes and permits them to drain when the water is drained from the tank. 3, Cover of tank with hole at center for inserting a recording thermometer. 4, Assembled teat cups on tray. 5, Long milk tube on tray. 6, Steam connection to tank. 7, Drain pipe. conducted by the writers support the conclusion, that heat sterilization as recommended in this circular gives very satisfactory results ; the use of chemical sterilization, in addition, is therefore unnecessary. • Results indicate that chlorine solutions of proper strength are ex- cellent for sterilizing clean metal or rubber surfaces. One must remem- ber, however, that crevices form in rubbers which have been used for some time and provide a lodging place for milk solids. These solids combine with chlorine and render it ineffective in the destruction of bacteria. A chlorine solution, furthermore, loses its strength readily in the presence of milk solids, in sunlight, and at warm temperatures. Hence, unless its strength is protected, its efficiency in destroying bacteria cannot be depended upon. The solution should be frequently tested for available chlorine in order to determine its sterilizing value. During the warm summer months the chlorine solution may lose its strength so rapidly that bacteria in the rubber tubes are not destroyed. At such times, the strength of the chlorine solution may well be doubled 8 California Agricultural Extension Service [Cir. 69 at the time it is prepared, since this precaution has proved effective in avoiding irregularities in the bacterial content of the rubbers. One investigator 7 has used sodium hydroxide or lye solution as a satisfactory chemical sterilizing agent for milking machines. Our results with the use of this chemical show that sodium hydroxide of 0.4 to 0.5 Fig. 2. — Homemade chlorine or sodium hydroxide sterilization rack. A brown glass bottle should be used for chlorine solution in order to protect it from light. per cent strength will kill most of the bacteria present in milking ma- chine rubbers but that the bacterial content, on the average, will be somewhat higher than when chlorine solution is used of a strength of 200 parts per million. Lye solutions should not be used on machines having aluminum parts. The bacterial content of the milking machine rubbers was checked by passing sterile distilled water through the assembled units, consisting of the claws and rubbers, and then plating the water with standard agar after its agitation in the rubber tubing. 7 Parfitt, E. II. A study of methods of cleaning milking machines. Purdue Univ. Agr. Exp. Sta. Bui. 348:1-24. 1931. 1932] Care of Milking Machines 9 The bacterial counts of the rubbers sterilized by the recommended heat method averaged 3 bacteria per cubic centimeter of rinse water, while chlorine sterilization averaged 45, and sodium hydroxide aver- aged 148. INFLUENCE OF CHEMICAL AND HEAT STERILIZATION ON THE RUBBER PARTS The life of milking machine rubbers depends on many factors, such as quality and age of rubber, number of cows milked per day, numbers of sterilizations per day, treatment during sterilization, thoroughness of cleaning the rubbers, and size of teats of cows milked. In the investiga- tions referred to, factors influencing the life of rubber parts were kept as constant as possible. When the recommended method of heat steriliza- tion was used, and the cows were milked twice a day, the teat-cup rubbers had a life of 8 weeks, the short milk tubes 16 weeks, the short air tubes 23 weeks, and the long milk tubes 46 weeks. When the rubbers were sterilized twice a day with the chlorine solution, the teat-cup rub- bers lasted 13 weeks. Chlorine sterilization of the machines used three times a day resulted in a life of 11 weeks for the teat cup inflations, 14 weeks for the short milk tubes, 31 weeks for the short air tubes, and nearly a year for the long milk tubes. The life of the long milk tubes depends largely on the number of times they are stepped on by the cows and the number of times the ends are trimmed. Chlorine and sodium hydroxide sterilizations are almost equal in their effect upon the teat- cup inflation rubbers. OPERATION AND INSTALLATION OF MILKING MACHINES Before milking, the machines may be assembled and tested for air leaks by connecting them with the vacuum line. Air leaks, if present, can be detected by sound. Directions given by the various milking machine companies for the placing of teat cups on the animal and applying the vacuum should be carefully followed. Unless the teats are cleaned before milking, the dirt on them will be mixed with the milk while the machines are being operated. The udder of the cow should also be washed and wiped clean, or the hands of the milker will become soiled and will contaminate the milk when applying the teat cups to the teats and while stripping. One of the objections to machine milking is the difficulty in detecting abnormal milk produced from cows with defective udders. By drawing a stream of milk from each teat into a separate container before apply- ing the machine, one may detect abnormal milk and thus prevent con- 10 California Agricultural Extension Service [ Cir - 69 tamination of the machine and the milk. Such cows should be milked by hand after the milking of the other cows is completed. As a precaution against the teat cups dropping from the teats, a cord may well be passed over the cow's back and beneath the claw of those machines so equipped. This supports some of the weight and lessens the probability of the teat cups being displaced. Such a precaution is especially desirable when the cow's teats are small or when the rubber teat-cup inflations lose their elasticity. In case the teat cups should become disconnected and drop to the floor, the vacuum line should be closed immediately to prevent drawing con- taminating material off the floor, and the cups should be rinsed in cold, and then hot water, before milking is resumed. After the milk ceases to flow in a constant stream or when the bulk of the milk has been removed, the vacuum is turned off, and the teat cups are drawn from the teats. Stripping in a small-top pail will markedly reduce the contamination from the udder. When a pail is used to milk two or three cows without emptying and becomes filled, milk or foam is sometimes drawn into the stanchion hose and air line. Milk may also enter the stanchion hose and vacuum line as a result of improperly connecting the teat cups with the claw. If the short milk tubes and air tubes are reversed, milk will be drawn into the vacuum line. Since this may happen, the stanchion hose should be brushed regularly with washing solution to remove the milk solids. The stanchion hose does not require sterilization but may be hung in a clean place to dry. In the same way, milk may be drawn into the vacuum pipe line. As an aid in cleaning, the pipe line should be installed on the stanchion with a slope from one end of the barn to the other, and it may slope either to or away from the vacuum pump. A moisture drain valve at the lower end of the pipe line will permit accumulated milk to drain from the vacuum line as soon as the vacuum pump is shut off (fig. 3) . When the vacuum line is installed on the stanchions, the pet cocks used for connecting the stanchion hose should be placed in a position near the top of the pipe line, and the pet cock made to turn downward (fig. 3) . This precaution will prevent the drainage of milk from the pipe line into the stanchion hose during milking. If the vacuum line is not cleaned at intervals, milk solids will accumu- late, dry on the surface, and in time partially or completely close the pipe line, thus producing an insanitary condition and preventing the securing of sufficient vacuum at the ends of the lines for proper opera- tion of the machines. The pipe line should be rinsed at least once each 1932] Care of Milking Machines 11 week with clean water, preferably by the use of a hose ; and if a steam boiler is in use, a connection should be installed in the barn and the pipe line steamed after being rinsed with water once each week. If steam is not available, a solution prepared with warm water and dairy washing powder may be used for cleaning the pipe line. The pipe line should be filled and the solution allowed to remain for one hour before being drained out. If the solution is drawn through the pipe line by vacuum after soaking in the line, its volume should not be greater than that of the moisture trap. Inflation rubbers, tubes, and other necessary parts that may have to be replaced should be kept in stock to avoid delays and inconveniences. Inflation rubbers may become cracked in the seams or perforated as a result of wear and require immediate replacement. Similarly, the claws and other parts may become damaged by being stepped on by the animals. The keeping of extra parts, therefore, will save a good deal of annoyance in the operation of milking machines. Flat-bottomed pails used on concrete floors may wear and the bottoms become perforated. In that case, dirt and moisture may be drawn from the floor into the pail, thus causing objectionable contamination. Care in preventing such occurrences is necessary to secure satisfactory results. Pulsators should never be put into the water. Once each month the pulsator should be cleaned by rubbing the surfaces with a cloth mois- tened with kerosene. ACKNOWLEDGMENTS Acknowledgment is made to the Division of Animal Husbandry for the facilities provided at the dairy barns for conducting the experiments upon which this publication is largely based. The authors wish also to acknowledge the cooperation of Mr. Orval Borland, who carried out the regular cleaning and sterilization of the milking machines. 12 California Agricultural Extension Service [Cm. 69 s n 1 im 1 *"* : - ■sr Hi jf^ B r % K ■ '"': - ..- : . I (VAT] : -' : *-' ? ;r""' : ' : " ; ''"' : ;" 1 ; Fig. 3. — The first step in the cleaning of milking machines is rinsing with cold water. Draw 1% gallons of cold water through the machine immediately after the last cow has been milked in order to remove the milk solids before they dry on the rubber surfaces. 1, Moisture drain valve at lower end of pipe line. 2, Pipe- line stanchion base cock fitted to top of pipe line to prevent leakage into stanchion hose. 3, Vacuum gage. 4, Moisture trap. 1932] Care of Milking Machines 13 Fig. 4. — The second step in the cleaning of milking machines is rinsing with hot water. Draw 1% gallons of hot water (165°-170° F) through the machine to melt and remove the fat. 14 California Agricultural Extension Service [Cm. 69 '» Fig. 5. — The third step in cleaning milking machines is the brushing of the inner surface of all milk tubes and inflation rubbers after each milking. Warm water containing washing powder should be used. 1932] Care of Milking Machines 15 Fig. 6. — Use the proper size of brush for each size of rubber and inflations of the milking machine. 16 California Agricultural Extension Service [ Cir - 6 9 4 | „* / ■ f|\ tt W B |BWi|[||| ■HBHMl m ':'•■.,.'■•>..:.-•■■. 1 i 1 ■ i -IBl - H. B 1 M***-* jsJIB Fig. 7. — The metal parts, as well as the rubbers that come in contact with milk, should be thoroughly washed after each milking. 13m-ll.'32