Farm Dairy Instruction: Cleaning Milking Machines and Dairy Equipment

New Zealand Journal of Agriculture, Volume 79, Issue 5, 15 November 1949, Page 487

Farm Dairy Instruction: Cleaning Milking Machines and Dairy Equipment

By

W. G. BATT,

Supervisor of

Dominion Farm Dairy Instruction, Department of Agriculture, Hamilton.

THE milking machine and J- other equipment provide a serious source of contamination if effective methods of cleaning and sterilisation are not followed.

Research and practical trials have shown that the detergents and methods advocated in this article are best suited to New Zealand requirements.

THE releaser type of milking machine, used by the New Zealand farmer, in which the milk is lifted to an overhead pipe by vacuum and released in a room separate from that used for milking, has considerably more metal and slightly more rubber than the bucket type of machine, favoured in other countries. It is difficult to formulate a complete method of cleaning the two component materials, metal and rubber, as a method best suited to cleaning metal may not be the best for rubber. For instance, regular brushing of metal is necessary to prevent the formation of encrustations of casein and minerals, but it will quickly destroy the surface of rubber and create conditions favourable to the harbouring of bacteria. Fat, including butterfat, is most destructive to rubber, and a detergent which will prevent milk film and deposits on glass and metal will not remove fat from rubber. Milking machine rubberware will absorb fat rapidly; rubberware subject to pulsation will absorb half or more of its own weight within a relatively short period. Once fat is absorbed, destruction of ' the surface of the rubber begins and small cracks, which harbour bacteria, appear and get progressively worse until the rubber reaches a sponge-like condition in which it cannot be effectively cleaned or sterilised.-

Porous Material Harmful

It is most important to remember that for handling dairy produce the use of anything porous must be avoided at all costs, because porous material harbours bacteria and makes sterilisation difficult and often impossible; wood or concrete in contact with milk will harbour immense numbers of bacteria. Metal must be smooth and properly coated with tin, and rubber must have a smooth, hard surface, if the conditions under which these materials harbour . bacteria are to be avoided. Because the milking machine is comprised largely of metal and rubber, both materials must be considered in reference to cleaning methods. Research and trials by the Dairy Division have had as their objective

the formulation of a method which will prevent contamination from an accumulation of milkstone and mineral stone on metal, and intense contamination from deterioration of rubber by the penetration of fat. As metal in good condition has a smooth, hard surface and presents no problem if simple cleaning methods (proper flushing, regular brushing, and sterilising with boiling water) are used regularly, the cleaning of rubber becomes the most important aspect. Rubber requires different treatment from metal, and usually it is the rubber parts of a milking machine which are found to be unclean because operators have not recognised the fundamental cause —absorption . and penetration of fat. The objective should be to use a detergent and a method of cleaning which will retard the penetration of fat into rubber and the consequent destruction of its interior surface. Exhaustive trials, supported by analyses of rubber after use, show that an alkaline wash is best, the most effective detergent being caustic soda, not because of its strength as a cleanser, but because of its ability to remove all trace of fat by its power of binding fat particles. The metal and rubber on a milking machine may be in good condition, but if proper cleaning methods are not used regularly or the cleaning procedure is unsatisfactory, contamination and consequent harbouring of bacteria will arise from two conditions: The formation of encrustation of milkstone and mineral stone on metal and the penetration of fat into rubber. Milkstone is the casein of milk which has become attached to metal in the form of encrustations. It is caused by inefficient flushing of the milk from the equipment, the casein of the milk being burnt on to the metal by the heat generated by the subsequent boiling flushing solutions. Mineral stone is caused by small deposits of minerals common in some water lodg-

ing on metal. They occur first as sediment and finally become firmly attached by heat and a mixture of milk deposits,' including fat. These conditions, both of which are a serious contaminating influence, can be avoided by sufficient flushing and regular brushing. Rubber is not . affected by milkstone because it does not absorb and hold heat as does metal. The rubber parts of a milking machine should not be brushed, because it is unnecessary and because the regular use of a brush will scratch and score the inside surface, assisting in the lodgment and penetration of fat and causing a ' porous condition, which should be avoided. All metal parts used in handling dairy produce should have a bright, shining appearance. If dull, they are coated in deposits or have lost tinning. The former can be removed with spirit of salt, but metal devoid of tin must be replaced. Milking Machines ' On the modern and larger milking machines a self-draining vacuum tank is fitted next to the vacuum pump to facilitate the cleaning of the milk and air systems by flushing. The top chamber of the releaser is filled with liquid by interrupting the releaser pulsator and the surplus taken to the vacuum tank, thus cleaning the vacuum piping in this section. ' The liquids are discharged by breaking the vacuum at any point on the machine, and the method has the advantages ,of conveniently flushing both the milk and air systems and of assisting to maintain the temperature of the solutions used. A simple method of cleaning a milking machine is described in the following section of this article, but it must be practised regularly. Where this is

done stone will form on metal only in exceptional cases, and rubberware, with the exception of inflations, will remain effective and sanitary for up to 6 years. The steps in the cleaning of the machine are: — 1. Before milking is begun draw cold water through each set of teat cups. This will wet the parts and help to prevent milk film adhering to the metal. Lift the cups in and out of the water, allowing an intake of air to provide greater rinsing and flushing.

2. After milking remove all dirt from the outside of teat cups and claws by hand brushing them in a warm caustic soda solution.

3. Stop the releaser pulsator or disconnect the releaser rubber and draw one bucket of cold water through each set of teat cups. This will fill the releaser and remove milk deposits from all parts before the boiling solutions are applied. Lift the cups in and out of the water to allow an intake of air and to produce a surging effect. Insert in the main milk pipe a traveller brush or cleaner attached to a cord and allow it to travel to the releaser under vacuum. Draw it back against the air pressure to brush the pipe thoroughly. Break the vacuum to discharge the water from the releaser and vacuum tank.

4. Draw 1 gallon of boiling water and caustic soda solution at the strength of 1 level teaspoon of caustic soda to 4 gallons of boiling water through each set of teat cups. Lift the cups in and out of the solution to allow an intake of air and to produce a surging effect. Better results and greater sterilisation are i obtained by immersing 2 sets of cups in the solution simultaneously. Break the vacuum to discharge the solution from the releaser and vacuum tank. (The solution from the releaser is discharged into a container and used for other purposes.)

5. Through each set of teat cups draw . 1 gallon of clean boiling water. Lift the cups from the water first and once only to flush out the caustic soda solution. Generate the utmost heat and give the most effective sterilisation by leaving the cups immersed and preventing an intake of cold air. Turn off vacuum taps before removing the cups from the liquid. Better results and greater sterilisation • are obtained by immersing 2 sets of cups in the boiling water simultaneously. Break the vacuum and discharge the water from the releaser and vacuum tank.

6. Treat the pulsator and vacuum systems in the same manner by drawing the solutions through the systems from the claw air rubber or from behind the inflations. The rubber connecting the releaser tothe releaser pulsator must alsohave daily attention. 7. Brush the metal pipes regularly with a to-and-fro motion. A brush and cord, ball of horsehair and cord, or a rubber cleaner and cord are all suitable for cleaning the main milk pipe under vacuum. 8. Wash the outside of teat cups and . rubbers with caustic soda solution collected from the -releaser and rinse them. Disconnect them from droppers and hang them in a clean, > dry place, protected from sunlight. 9. Scrub the releaser, vacuum tank, separator parts, and utensils with a brush and sterilise them in boiling water. 10. To allow a • circulation of air remove all rubber plugs from piping and leave all ports and the vacuum tank open. Analyses, following practical trial, have shown that the penetration of fat into rubber is very rapid and very considerable; milk elevator inflations, have been found to absorb 6 per cent, (by weight) of fat in 2 months and teat cup inflations. much more. Consequently, it is essential to remove all trace of fat after each milking, and tests have shown conclusively that completely satisfactory results can be obtained only by using the boiling water-caustic soda method twice daily. Analyses of rubber after the use of this method twice daily have shown no penetration of fat, but following its use during a comparable period once

daily penetration of fat has been considerable. When washing soda and -similar cleansers were used absorption of fat increased greatly. The primary objective in cleaning •dairy equipment is to destroy bacteria and remove fat. Caustic soda is the only detergent which will effectively remove fat from rubber. It is also a germicide, and bacteria will be destroyed by its use and by sterilisation with boiling water. There are many cleansers, including washing soda, which are very effective as water softeners and are useful if used in conjunction with caustic soda, particularly where hard water is common, but they are not effective as sole cleaning agents. With the exception of stainless steel .all metals used in dairy equipment, unless properly coated with tin, are porous, and being porous they harbour bacteria and also impart metallic flavours. The effect of milk acids and long usage will cause tinning to be removed gradually and in this condition the metal has a highly contaminating influence. No bare metal should be used in handling dairy produce and all parts so affected must be retinned or replaced. Milk Pumps and Elevators Inspection frequently reveals much more serious contamination in milk pumps and elevators and in the connecting pipes and rubbers than in the milking machine, and sometimes the last named is clean though the other parts mentioned are affected. An in-

vestigation has shown that this is due to the common fault of flushing these units and parts simultaneously with the milking machine and with the same solutions. Trial and experiment have shown that these devices can be kept in as clean condition as the machine if they are treated separately and with the same procedure. nr^sent m on pumps and elevators at present on the market are regarded as satisfactory for their purpose, but one cleaning operation, by flushing the milking machine and ' milk elevator, is insufficient and unsatisfactory, chiefly because of the considerable fall in temperature of the solutions by the time they reach the milk elevation equipment. While the boiling detergents and rinses are under vacuum in the milking machine they maintain largely their efficiency, but as soon as they are released into cool air between the milking machine and milk elevator their power to cleanse and to remove fat is diminished and their value as sterilising, agents is lost. The position is aggravated in cases where the solutions are allowed to run over a milk cooler before reaching the milk elevator The practice of taking milk elevators to pieces daily and cleaning the in-

flations and parts by hand is not recommended and the same methods and detergents as are used in cleaning the milking machine should be employed, using the following procedure: — j Draw 1 bucket of cold water through the milk elevator and its connections. 2 Pu t through J gallon of. boiling water to which has been added caustic soda (1 level teaspoon to 4 . gallons of water). 3. Rinse with J gallon of clean, boiling water. . , • . J . . The important point is that this equipment must be treated independently of the milking machine. .. ; c;4.±: nnc _. n Milldnn Mackinac Sittings on Milking Machines Where a part of a milking machine is difficult to take apart it is usually found in an unclean condition because it is inconvenient to give it proper and regular attention. ' The number of releasers unclean and The number of releasers unclean and coated in milkstone, especially in the top chamber, coincides with the numher which are difficult to take apart

because of unsatisfactory unions connecting the releaser to the milk and air piping and to unsatisfactory releaser brackets.

The fittings used on milking machines, particularly the unions connecting the lengths of milk piping to each other and to the releaser, must be such that these parts can be taken apart conveniently. Many types of unions used on milk piping and releasers are unsatisfactory because spanners and tools have to be used to disconnect and take down these vital parts. The screwed, wing-nut type is favoured, as it can be loosened easily and conveniently without tools.

In their own interests farmers should insist on their milking machines being fitted with unions and brackets of a type which will facilitate the taking down of piping and releaser for regular inspection and cleaning, v

Cleaning of I-bail Bucket Machines

As 1-bail bucket milking machines have no releaser and no vacuum tank, there is no simple method of cleaning all parts by flushing and the methods advocated for machines of larger size

must be modified slightly. The glass vacuum jar provided on most models has some value as a detector,, but .it has insufficient capacity to accommodate the liquids required to flush the air section adequately and there is a tendency for the glass, through expansion, to break when filled with boiling water. There is considerable contamination in the vacuum sections ■of these machines, owing to milk vapours being constantly drawn from the bucket through the vacuum rubber to the vacuum pump. Therefore, the rubber and vacuum jar require regular and thorough cleaning. The milk system, comprising the teat cups .and milk rubbers, should be treated by flushing to the vacuum bucket, using the same detergents and the same methods as recommended for larger machines. After this has been ■done the pulsation rubber leading from the cups to the pulsator and the ’vacuum rubber . leading from . the bucket to the vacuum jar should be disconnected,' brushed in caustic soda solution, and rinsed. The glass vacuum

jar is then taken apart and cleaned and the rubber ring washed in caustic soda solution to , retard absorption of fat and replaced to prevent it from stretching. The teat cups and rubbers should be kept in a clean, dry place protected from sunlight and the glass jar and bucket on a clean bench in the open air. Separator Parts and Utensils The separator parts, especially the discs, and the cooler, milk vat, and other utensils can be a source of considerable contamination unless effectively cleaned and sterilised. Unless fat is removed completely, very unsatisfactory flavours develop from oxidation and from the development of bacteria. No metal parts of this kind can be cleaned thoroughly without brushing and they must be scrubbed regularly with a hard brush. An alkaline wash .is the most suitable for cleaning the equipment and one of the common preparations or washing soda is generally used. A soap

solution is also useful, and a weak solution (1 level teaspoon to 8 gallons of boiling water) of caustic soda will give excellent results.

Good results are obtained by collecting and aggregating the caustic solution used in cleaning the milking machine with the boiling water used in flushing it. By the addition of the water used in the final flushing the strength of the caustic solution previously used in the milking machine is reduced from 1 teaspoon to 4 gallons of water to 1 teaspoon to 8 gallons.

All tinware and utensils after being scrubbed adequately in an alkaline wash must be sterilised. Boiling water is a suitable rinse and immersion in it will destroy bacteria. All metal parts should be kept on a clean, dry bench in the open air.

Because transport to the manufacturing dairy causes considerable agitation of milk and cream, it is essential that the cans used for this purpose should be properly and completely tinned and cleaned and sterilised effectively. Pitted metal in cans and incomplete sterilisation of them are the cause of much poor-quality produce. The can-washing machines of dairy factories are not intended to complete the cleaning of cans, which remains the responsibility of the supplier. Milk and cream cans must be scrubbed daily in an alkaline solution and sterilised with boiling water. After cleaning they should be kept in clean, fresh air to drain and dry completely.

Appliances for Boiling Water

Almost all dairy farming districts are served by electricity and the electric cylinder is the most common appliance for boiling water. Coppers mainly are used in districts not connected to electric supply systems. Whatever appliance is used it is essential that it should produce boiling water when cleaning of equipment is to begin. The copper boiler, properly bricked in and under cover, is particularly useful where fuel is plentiful,

as adequate boiling water is available at any time and it provides a means for the sterilisation of utensils by immersion. Electric water-heating appliances are simple and convenient, but the capacity of the cylinder and of the element must be sufficient to provide boiling water by the time it is required. This is not always possible during periods when electricity must be conserved; then it becomes necessary for the operator to adjust the intake of cold water to the cylinder to the reduced supply of electricity. Warm or hot water, however plentiful, is useless for sterilising milking machines and dairy equipment, and if there is not sufficient power to bring the water to boiling point it will be more satisfactory to reduce the quantities of water recommended for cleaning to ensure that the supply from the cylinder reaches boiling point at the required time. A small quantity of boiling water will destroy bacteria; a large quantity of hot water will not. Removal of Milkstone and Mineral Stone Encrustations of milkstone and mineral stone are a serious contaminat-

Journal of the British Grassland Society

The Journal has been instituted as a medium for the publication of the results of research and practical experience in the realm of grassland husbandry. CONTENTS OF VOL. 4, No. I, 1949. Experiments with leys and permanent grass. D. A. Boyd. Herbage sampling errors and grazing trials. J. 0. Green. , Evaluation of British grassland. T. E. Williams. Statistical estimation of . the output of different types of pasture in Finland. A. Jantti. The provision of fodder in a Mediterranean environment. R. 0. Whyte. The establishment of Autumn sown legumes. B. F. Martin. Environment and germination in grass seeds. H. G. Chippindale. Observations on the, effect of artificial flooding on certain herbage plants. A. G. Davis and B. F. Martin. 1 - The determination of the acidity and total nitrogen in silage samples by improved and quicker methods. A. J. G. Barnett. Research and problems overseas. , Reports and notices of meetings. Book Reviews. Obituary Notices. List of Members. ' This journal Is published quarterly. Subscription: Vol. I, 10s.; annual subscription thereafter 20s. .Orders to Secretary, British Grassland Society, Agriculture .Research Building, Penglais, Aberystwyth, Wales. ■>..

ing influence, because they harbour bacteria and prevent effective cleaning, and sterilisation.

The number of milking machinesaffected by milkstone and mineral stone coincides with the number not equipped with brushware. The contaminating influence of the encrustations and the difficulty and inconvenience of removing them from milking machine piping can be obviated by regular flushing and brushing. Where the piping and metal parts of a milking machine or the metal of other equipment is not bright and smooth and . is coated in these deposits all such encrustations mustbe removed if the quality of dairy produce is to be protected. Any powerful acid will soften the deposits, but experience has shown that a weak solution of hydrochloric" acid (spirit of salt) is the most suitable. The pro- ( cedure is as follows: — 1. Dismantle the piping and plug oneend of each length. 2. Pour into each length in turn 1 breakfast cup of a solution of spirit of salt and cold water (1 part spirit of salt and 2 parts water) and plug all inlets. 3. Allow the solution to remain until the deposits are softened. This will require half an hour or more, and i the piping should be turned occasionally to spread the acid over the whole surface. 4. Remove the deposits, when softened, . with a hard brush and immerse thepiping or metal parts immediately in an alkaline solution (washing soda or caustic soda is suitable) to neutralise the acid and prevent damage to the tinning. Rinse with clean, boiling water. Separator'discs and parts, releasers, milk vats, and coolers, are treated in the same manner, but the acid solution is applied with a soft brush or cloth. Properly treated, piping and metal parts should be clean and bright and will remain in this condition if the cleaning methods recommended are followed regularly.