Summary 1. Using the phosphatase test, as modified by Scharer, it was found possible to detect variations in the time and temperature of pasteurization of ice cream mixes, provided they had not been colored or flavored. 2. The use of all raw or partially pasteurized milk products in building a mix had no effect on the final phenol value, if the mix was pasteurized at temperatures of 150° F. or above. However, at temperatures of 147° F. or below, the mix made from all raw milk products gave a considerably higher final phenol value than in the case of the mix made from partially pasteurized milk products. 3. Subjecting raw milk and ice cream mix made from all raw milk products to the same heat treatment by heating to temperatures of 150° F. or above and holding for 30 minutes resulted in the same final phenol value for both the milk and mix. Temperatures below 150° F. resulted in a higher final phenol value for the ice cream mix than that of the milk. 4. The condensing process decreased the amount of phosphatase enzyme present. 5. Increasing the serum solids content of the mix had no effect on the final phenol value when the mix was pasteurized at 150° F. for 30 minutes. 6. Storing pasteurized, unflavored and uncolored ice cream mix at 40° F. for a period of two weeks did not appreciably alter the phenol value. 7. Storing unflavored and uncolored ice cream at −20° F. over a period of twelve weeks resulted in marked decreases in the phenol values of all the samples except those made from mix samples taken 20, 25 and 30 minutes after reaching 150° F. The samples heated for a period of time less than 20 minutes, however, still showed sufficient phenol content for them to be considered underpasteurized. 8. Pure vanilla had no effect on the phenol value while artificial and imitation vanilla compounds caused a slight increase and coumarin and vanillin caused appreciable increases in the phenol value of the mix. 9. Flavoring extracts (other than vanilla) added to the mix did not appreciably alter the phenol value, while the addition of “Cold-Pak” fruits increased the phenol value. 10. The addition of coloring material to ice cream mix in many instances affected the phenol value unless the coloring matter was precipitated with the protein upon the addition of the lead acetate. This, however, was not always possible. 11. Tests run on commercial samples of ice cream mix gave indication of complete pasteurization in all but one case.