ANNUAL REPORT, 1933 27 



Ice creams which are considered high in fat have a butterfat content of 18 

 per cent or more. In the manufacture of these rich ice creams two serious 

 difficulties have been encountered. One is an excessive viscosity which inter- 

 feres with efficient homogenization, cooling, freezing, and packaging. The other 

 is a very undesirable melting appearance. When served, the ice cream does not 

 melt into a creamy liquid but remains rigid as a whipped cream would. Often 

 a clear liquid oozes from the mass. This condition is undesirable because the 

 consumer often assumes that inferior ingredients have been used or an excessive 

 amount of stabilizer has been added. 



Results indicate that excessive viscosity can be largely prevented by using 

 higher pasteurization and homogenization temperatures (155 to 160° F.) and 

 homogenizing with a duo-valve machine. However, passing the ice cream mix 

 through both valves of a two-stage machine still permits considerable cluster- 

 ing of the fat globules. These clusters of fat globules materially increase vis- 

 cosit}'. Trials have been conducted with a reducing valve on the discharge 

 line of the homogenizer, carrying from 100 to 150 pounds of pressure as far as 

 the reducing valve. The ice cream mixture is released from further pressure as 

 it passes through the reducing valve. This additional treatment almost entirely 

 eliminates clustering of fat globules, and as a result the homogenized product 

 is sufficiently low in viscosity. 



Improvement in the melting appearance of ice cream high in fat content is 

 another benefit of the procedure just discussed, for the prevention of fat globule 

 clustering also improves melting appearance. At present a study is being made 

 with different sugars in the hope of decreasing the resistance to melting. It is 

 hoped that the use of glucose or some other simple sugar in combination with 

 sucrose will prove beneficial in securing a desirable melting appearance of ice 

 creams high in fat content. 



The Vitamin C Content of Strawberries and Strawberry Ice Cream. (C. R. 



Fellers, Horticultural Manufactures, and M. J. Mack.) This study was planned 

 to determine whether or not preservation of strawberries by freezing or their 

 subsequent use in strawberry ice cream decreased the vitamin C content of the 

 fruit. Bio-assays were conducted with guinea pigs on fresh and frozen straw- 

 berries and strawberry ice cream. The study, which was completed during 

 the past year, showed that preservation of strawberries by freezing, with or with- 

 out sugar, has no harmful effect on the vitamin C content of the fruit. The 

 incorporation of strawberries into ice cream and the rigorous beating during the 

 freezing of the ice cream caused no measurable loss of vitamin C. This is attribut- 

 ed to the low temperatures at which agitation, air incorporation, and storage 

 of the ice cream takes place. 



A Study of the Changes That Occur in the Storage of Frozen Sweet Cream. 



(H. G. Lindquist.) Some progress has been made, but thus far no methods 

 have proved satisfactory in measuring the changes that occur in frozen cream. 



The Comparative Efficiency of Electrically Operated Tanks versus Ice in the 

 Cooling of Milk. (J. H. Frandsen.) Where eiectricit\ was used in cooling four 

 cans of milk from 90° to 45° F., it was found that 1.2 KWH were required for 

 each 100 pounds of milk; and when ice was used, 40 pounds of ice were required 

 to accomplish the same results. Comparison in dollars and cents can best be 

 made in each locality by using the prices for electricity and ice that prevail in 

 the local communitv. 



