ICE-CREAM STANDARDS 189 



in the regular testing and read the percentage of fat 

 directly. 



If charring has interfered with the fat reading, add 

 ether after whirling to dissolve the fat, and draw off the 

 ether solution into another bottle. Evaporate off the 

 ether, fill with hot water and again whirl and read. This 

 latter method should not be resorted to except in cases 

 of necessity. It is always better to run the test over, 

 provided there is enough left of the original sample. 



2. Modified Babcock Method. Ice cream can be tested 

 successfully by using sulphuric acid, provided certain pre- 

 cautions are observed. The writers have obtained good 

 results by using the following method. Melt the sample 

 slowly at a low temperature to a creamy consistency; 

 quickly weigh 9 grams of it into a milk bottle. Add about 

 twelve cubic centimeters soft water, mix, then succes- 

 sively add small quantities of sulphuric acid, mix and let 

 stand to permit the acid to act. The action of the acid 

 is indicated by the color of the mixture, and when this 

 assumes a strong coffee color the reaction has gone far 

 enough and no more acid is required. If the color con- 

 tinues to darken, add a small quantity of soft water to 

 prevent charring. 



Bacteria in Ice Cream. The subject of bacteria in ice 

 cream has received attention only during the past few 

 years. There is a popular belief that, because cream is 

 frozen, it cannot decompose and that the organisms origi- 

 nally in the cream are either killed or rendered harmless 

 by the continued low temperature. However, experiments 

 show that bacteria do remain virile and that certain types 

 even proliferate at sub-freezing temperatures. The bac- 

 terial content of ice cream, then, is a matter of importance 

 from a hygienic standpoint. 



