HIGHER AGING TEMPERATURES IN THE MANUFACTURE 



OF ICE CREAM 



By W. S. Mueller, Assistant Research Professor, and J. H. Frandsen, Professor, 

 Department of Dairy Industry 



INTRODUCTION 



It is a general practice in tiie ice cream industry today to cool the mix to approx- 

 imately 40° F. over a surface cooler immediately after homogenization and then 

 to age from 4 to 24 hours at this temperature. The study of the effect of aging 

 on the properties of the mix and on the finished product has received much atten- 

 tion in both technical and practical ice cream investigation. 



The time factor in aging has received more attention than the temperature 

 factor because it appeared to be a more fertile field for investigation on account 

 of the possibilities of wide time variation. On the contrary, the temperature 

 factor in aging, or the practice of aging only at a low temperature, has remained 

 unchallenged for a long time, in all probability for two reasons: (1) It was thought 

 that the aging temperature was limited by bacterial growth to a narrow range, 

 32° to 40° F., and (2) it was thought that the desirable changes which occur 

 during aging were favored by low temperatures and therefore the lower the tem- 

 perature, the greater the benefits to be derived from aging. 



A previous study by the senior author (1) showed that a short aging period at 

 high temperature, followed by aging at a low temperature, increased the basic 

 viscosity and gel strength of both gelatin ice cream mixture and pure gelatin 

 water solution, when compared with a solution aged at a low temperature only. 

 Of the various high initial aging temperatures tried, 68° F. gave the maximum 

 increase in basic viscosity and gel strength. These results indicate that the 

 efficiency of the gelatin was increased by a short aging period at high temperature 

 followed bj' a low temperature aging period. 



The purpose of the investigation reported in this bulletin was (1) to determine 

 whether this increase in gelatin efficiency, due to initial aging at a high tempera- 

 ture, would be carried over to the finished product, and (2) to determine the 

 merits and disadvantages of aging at 68° F. when compared with aging at a low 

 temperature (38° F.). 



HISTORICAL 



So far as known no data have been published on the effects of aging time and 

 temperature on the quality of ice cream when an aging temperature above 50° F. 

 was used for definite periods of time. 



DePew (2) made a preliminary study of the effect of rate of cooling on the 

 viscosity of an ite cream mix. The time intervals allowed for cooling the mix 

 from 145° to 50° F. varied from 4 minutes to 50 minutes. After cooling to 50° 

 the mixes were aged at 40° for 24 hours. The results from four trials indicated 

 that the rate of cooling the mix after homogenization did not materially affect 

 its viscosity after being aged. 



