6 MASS. EXPERIMENT STATION BULLETIN 302 



of organism surviving pasteurization must not be overlooked. The probable 

 reason for no marked increase in titratable acidity and H-ion concentration is 

 that pasteurization destroys most of the lactic acid producing organisms and that 

 the mix is highly buffered. 



The Effect of Variations in Aging time and Temperatures of the Mix on Basic 

 Viscosity, Whipping Ability and Quality of the Ice Cream 



Four aging treatments were used in this experiment: — 4 hours at 38° F., 4 

 hours at 68° P., 24 hours at 38° P., 4 hours at 68° P. plus 20 hours at 38°. 



Aging for 4 hours at 68° P. was tried because of the recent recommendations 

 of a short aging period. Since in commercial practice it is sometimes inconvenient 

 to freeze immediately after the 4-hour aging period, this was followed by a low 

 temperature aging period. Although both 4- and 24-hour aging periods at a low 

 temperature (approximately 40°) have been studied extensively, they were in- 

 cluded in this experiment to serve as controls. 



A sweet cream mix testing 14 per cent fat, 10 per cent serum solids, 15 per cent 

 sugar, and 0.4 per cent gelatin (176 Bloom) was processed according to standard 

 procedure as given under experimental methods. Immediately after homogeniza- 

 tion the mix was divided and one portion cooled rapidly to 68° P., the remaining 

 portion to 38°. The 38° lot was again divided, and the two portions aged for 4 and 

 24 hours, respectively, in the cooling room (approximately 38°). The 68° lot was 

 aged 4 hours in a thermostatically controlled incubator, after which the mix was 

 cooled rapidly to 38°, then one portion was immediately frozen while the remain- 

 ing portion was aged for 20 hours at 38°. 



Table 3. The Effect of Aging at 68° P. on Basic Viscosity, Melting 

 Resistance, and Body and Texture 



(Sweet cream mix containing 14 per cent fat, 10 per cent serum solids, 15 per cent sugar, and 0.4 

 per cent gelatin (176 Bloom).) 



B.isic Per cent Numerical 



Aging Treatment Viscosity Melted after Rating for 



°M 13^ Hours Body and 



F.xposure Texture 



4 hours at 38° F. (ccntro!) 



4 hours at 68° F 



24 hours at .38° F (control) 



4 hours at 68° F. + 20 hours at .38° F 



Data on basic viscosity, melting resistance, and body and texture, as given in 

 Table 3, are the average of four trials. There was not much difference in basic 

 viscosity except in the case of the samples aged 4 hours at 68° plus 20 hours at 

 38°, which were noticeably higher. A comparison of the samples aged for 4 hours 

 and 24 hours at 38° agrees with previous findings that the basic \-iscosity in- 

 creases only slightly after 4 hours up to 24 hours aging. 



The ratings for body and texture show that aging at the high temperature 

 produced better results in both cases, with only a slight difference in fav^or of the 

 short aging period. A comparison of the samples aged at 38° only, showed that the 

 longer period produced slightly better body and texture. 



