ANNUAL REPORT, 1929 347 



From a study of the effect of aging on the texture of ice cream, the 

 following conclusions have been drawn: 



1. A high initial temperature in the aging period of the ice cream 

 mix favored the development of greater basic viscosity. 



2. The maximum viscosity was found to be imparted when the mix 

 was held at a temperature of 80 to 100°F. for two to four hours, with- 

 out agitation. 



3. The whipping property was decreased as the viscosity increased. 



4. The rate of melting was decreased as the viscosity increased. The 

 manner of melt-down was also influenced by difference in viscosity. 



5. The texture was improved as a result of greater viscosity develop- 

 ment. 



6. The influence of aging in ice cream has been attributed largely 

 to the factors affecting crystallization of the gelatin portion of the 

 product on the basis of the data obtained. 



The Quinhydrone Electrode in the Dairy Laboriatory. (Work started 

 by A. W. Phillips and now conducted by K. E. "Wright.) 



Further study indicates that since different kindls of milk bacterial 

 flora function in different ranges of pH, and since milk has a relatively 

 high buffer value and perceptible changes in pH do not take place with 

 appreciable additions of acid or alkali, the quinhydrone electrode deter- 

 mination of pH cannot be used for determining accurately the keeping 

 quality of milk. This work agrees with conclusions reached by A. W. 

 Phillips. 



The Utilization of Frozen Fruits in Ice Cream. ( M. J. Mack). This 

 project, now in its second year, is being conducted in cooperation with 

 the Department of Horticultural Manufactures. Fruits made available 

 in a study of cold packing methods are being used in the manufacture 

 of fruit ice cream. 



The varieties of fruits which were found to be most satisfactory for 

 freezing are likewise superior for use in ice cream. The optimum percent- 

 age of fruit in fruit ice cream was found' to be approximately 15 per 

 cent for cold packed strawberries; 8 to 10 per cent for raspberries, plus 

 a suitable amount of raspberry extract; 15 to 20 per cent for peaches' 

 in combination with an extract; and 12 per cent for cherries. The desir- 

 able ratio of fruit to sugar in the pack used for ice cream making was 

 found to be 2:1 and 3:1 for cherries and strawberries, and 3:1 for rasp- 

 berries and peaches. Fruit frozen without sugar or with corn sugar as 

 a substitute for cane sugar was unsuitable for use in ice cream. 



The fruit should be added to the ice cream directly after the freezing 

 operation is started in order to insure the maximum of fruit flavor and 

 even fruit distribution as well as more rapid freezing and whipping of 

 the ice cream. Fruit ice creams have a lower freezing point than plain ice 

 cream and should be drawn from the freezer at a temperature at least 

 1 to 1.5°F. lower than is necessary for plain ice cream. Fruit ice creams 

 cool faster in the freezer, whip faster, and require a shorter time of 

 brine flow than does plain ice cream made from the same basic mix. 



A Study of Frozen Sweet Cream for Use in Ice Cream. (M. J. Mack). 

 Sweet cream of good quality can be stored satisfactorily in the frozen 



