CONTAMINATION OF FOODS 14! 



cubic centimeters of water in a milk utensil is often suffi- 

 cient to add as many as 50,000 bacteria to cadi cubic centi- 

 meter of the milk when Ihc utensil is filled. It is doubtful 

 whether such a number of bacteria are ever added to the 

 milk through the introduction of dirt. 



All utensils should be washed after each period of use. 

 This is especially true of cream-separators. It is impos- 

 sible to remove the accumulation of organic matter that 

 collects on the wall of the bowl by running water through 

 the machine. It is essential that the machine be taken 

 apart, well washed, and thoroughly dried. Strainer cloths 

 should he washed as free from milk as possible, and placed 

 where they will dry quickly, so that no growth can occur 

 in them. 



Contamination from factory by-products. The cans in 

 which milk is transported to the creamery and cheese fac- 

 tory are also used to carry the whey and skim milk back to 

 the farm. This custom would have no disadvantage if the 

 cans were thoroughly washed before being used again. 

 This, however, is the exception rather than the rule, and 

 hence bacteria find their way from the whey-tank to the 

 cheese-vat. The great opportunity for the whey-tank to 

 become seeded with harmful types of bacteria or yeasts 

 makes this source of contamination of much importance in 

 the manufacture of cheese. Such trouble can be avoided by 

 heating the whey to a temperature of 140 to 155 F. as it 

 passes from the cheese-vat to the whey-tank, where it is 

 stored until the following day. If the volume of whey is 

 large, it will require considerable time for the temperature 

 to fall to a point where any bacterial growth can take place. 

 Heating to the above temperature is sufficient to destroy 

 most non-spore-forming bacteria. Whey so treated will be 

 sweet when returned to the farm, and will have a higher 

 feeding value than sour whey. It will also be free from 



