CLEAN MILK PRODUCTION 143 



one-sixth as much dirt gains access to the milk. With a little practice, 

 the small-top milk pail can be used as easily as the large-top pail. 



Clean Tinware. All the cans and pails that are used for milk should 

 be of metal, and all of the joints and corners should be completely filled 

 with solder. Wooden pails should not be used. To wash the tinware, 

 it should first be rinsed with lukewarm water, then thoroughly scrubbed 

 with brush, hot water and washing powder, and finally, either steamed 

 or rinsed with boiling hot water. It should not be wiped with a cloth, 

 but should be allowed to drain and dry. The heat of the steam or boiling 

 water will soon dry the tinware. 



Strainers. Where milk is produced in a clean way it is not necessary 

 to have a strainer. It is usually not desirable to have a strainer on the 

 milk pail, for the dirt collected will have all the injurious effect washed 

 from it into the pail during the milking. A strainer may be used on the 

 can or milk cooler. For this a cloth strainer, made especially for that 

 purpose and used only once, is satisfactory. The cheesecloth strainer 

 that is used from day to day contaminates the milk instead of purifying 

 it. A metal strainer is satisfactory. 



Handling the Milk. As soon as the milk has been drawn it should 

 be removed from the stable so that it will not absorb odors. A convenient 

 milk-room should be provided. This room should be clean and free from 

 dust and odors. The milk should be cooled at once. Under the best of 

 conditions, some bacteria or germs get into the milk, and the problem, 

 therefore, is to prevent these bacteria from increasing in number. At a 

 temperature of 70 F. one bacterium may increase to two in twenty min- 

 utes, but at 50 F. or lower it requires a much longer time. One bacterium 

 at 50 F. may increase in twelve hours to six or seven, while at 70 F. 

 it may increase to six or seven hundred. Since, therefore, there are several 

 hundred bacteria in every cubic centimeter of good milk, some realization 

 may be had of how many thousands of bacteria will be developed in ten 

 or twelve hours at 70 F. The following table, prepared by Stocking, 

 shows the importance of cooling milk at once to a low temperature. The 

 milk that was used in this experiment contained a low percentage of bac- 

 teria when produced. 



EFFECT OF DIFFERENT TEMPERATURES UPON THE DEVELOPMENT OF BACTERIA 



IN MILK. 



Temperature Maintained Bacteria per c.c. at 



for 12 Hours. end of 12 Hours. 



40 F 4,000 



47 F 9,000 



50 F 18,000 



54.5 F 38,000 



60 F 453,000 



70 F 8,800,000 



80 F 55,300,000 



Coolers. There are various styles of apparatus on the market for 

 cooling milk. These are called coolers. They are arranged so that the 



