46 MASS. EXPERIMENT STATION BULLETIN 388 



the mineral salts present, and the melting characteristics of the product. Other 

 factors are also involved, such as the serving temperature, the type of flavoring 

 used, and the ratio of solids to sugar in the ice cream. 



A Study of New Stabilizing Materials for Ice Cream. (M. J. Mack and A. M. 

 Shipley.) Several new stabilizers have recently been developed and already are 

 used to some extent in ice cream. The stabilizer employed affects a number of 

 properties, such as the viscosity, titratable acidity, and whipping ability' of the 

 mix, and the flavor, body and texture, and melting properties of the ice cream. 

 The object of this investigation is to compare the effectiveness of the new stabiliz- 

 ers with those already known to be desirable in ice cream. 



Among six stabilizers thus far observed, two were as effective as gelatin or sodium 

 alginate in producing mix viscosity and firmness of body in ice cream. They 

 allowed satisfactory whipping of the mix and permitted normal melting of the 

 product. The chief difficulty thus far encountered is that some of the newer 

 stabilizers are somewhat lacking in solubility. The work will continue with a 

 study of the effects of each active material employed, with the object of finding a 

 combination of stabilizing materials more satisfactory than those now available. 



The Appearance of Melted Ice Cream. (M. J. Mack.) The melting charac- 

 teristics of ice cream have recently received more consideration, as is evidenced 

 by the fact that the new score card approved for ice cream by the American 

 Dairy Science Association allots 5 points to this item. Severe defects in melting 

 appearance usually are due to loss of stability of the casein in the ice cream, while 

 minor defects ma)' be due to other causes. 



Slight increases in the acidity of mixes cause ice cream to appear curdy or 

 "whey off" when melting, if normal homogenization pressures are maintained. 

 Standardization of the acidity by the addition of som.e suitable alkaline material 

 does not injure the melting appearance in ice cream of average composition 

 unless the original acidity is greater than approximately 0.24 percent. The 

 melting characteristics are affected to a lesser degree by such factors as the com- 

 ponents used, the percentage composition, the methods of freezing, and so on. 



A Comparison of the Electric and Vat Methods of Pasteurization. (L. D. 



Lipman, J. H. Frandsen, and H. G. Lindquist.) Split batches of raw milk were 

 pasteurized in an electric pasteurizer at 162° for 16 seconds, and in a spray vat 

 at 143° for 30 minutes. The following conclusions may be drawn. 



1. The reduction in vitamin C content of milk was less rapid in the electric- 

 pasteurized milk than in raw or vat-pasteurized milks. 



2. The electric method gave better, that is less, phosphatase units than the 

 vat method. 



3. Vat-pasteurization decreased the cream volume, while the electric method 

 gave the same cream line as that of the raw milk. However, the difference between 

 the two methods of pasteurization was so small that no definite conclusions 

 should be drawn as to which of the two methods results in the smaller decrease 

 in cream volume. 



4. There was no significant difference in the efficiency of bacterial reduction 

 between the vat and electric methods of pasteurization. With som.e milks the 

 electric method seemed to show the higher percentage kill, whereas with other 

 milks the vat method seemed to show the higher percentage kill. A probable 

 explanation for this is that the types of bacteria or bacterial flora present in the 

 milk will affect the percentage killed by pasteurization. For example, evidence 

 seems to show that thermophilic bacteria are killed by the high-temperature- 

 short-time pasteurization but survive and may grow at vat-pasteurization tem- 

 peratures. The reverse seems to be true with the thermoduric types of bacteria. 



