CLEANLINESS 21 



water, ivory or a similar soap may be applied with 

 a soft cloth, using care not to loosen too much paint. 



17. Rinsing and scalding. — If the utensils are put 

 into a vat of boiling water, the washing solution is rinsed 

 off. If boiling water is applied through a hose, as in case 

 of a vat or a pasteurizer, the same result is obtained. In 

 case steam is employed to scald, the utensils should be 

 thoroughly rinsed before scalding, otherwise white streaks 

 of the powder will remain on the utensils. 



In this step in the process of cleaning, the most im- 

 portant factor is the killing of bacteria. Thorough 

 scalding of utensils is a practice of good dairying. The 

 value of complete scalding is well known in all industries 

 where the presence or absence of bacterial life is important. 

 A mistake is often made in utilizing water that is not 

 sufficiently hot to kill bacteria. A short experiment was 

 made on the effect of warm water versus hot water for 

 killing bacteria. Two buttermilk pails were cleaned in 

 the same way. One was held in a tub of water for one 

 minute at a temperature of 130° F. The temperature of 

 the water in the tub was then raised to 180° F. and the 

 other pail was submerged for one minute. A bacterio- 

 logical study was made later. It was found that over two 

 hundred times as many organisms were left alive in the 

 first pail as in the second. A temperature of 130° F., or a 

 few degrees above, is not sufficient to destroy bacteria. 

 The presence of steam, which may appear at this time, is 

 not a certain indication of the scalding temperature. 



The question often arises, " What is the best tempera- 

 ture for thorough scalding, and how long should a dairy 

 utensil be exposed to a given temperature ? " Data are 

 found in Table VIII which show that there is very 

 little difference in the number of bacteria killed, on the 



