48 MASS. EXPERIMENT STATION BULLETIN 355 



The Digestibility of Ctiocolate-Flavored Milk in Vitro. (W . S. Mueller and L. 

 D. Lipman.) The purpose of this study was to check, if possible, the results of 

 the animal feeding experiments. Digestion experiments have been made with 

 plain milk and chocolate milk containing 1, 2J^, and 4 percent Dutch process 

 cocoa. Digestion was carried out with artificial gastric juice, in a rotating mach- 

 ine set in an incubator at 37° C, in order that digestion might go on under con- 

 ditions somewhat approaching those of the stomach. Samples were taken out 

 before digestion and after digesting for 2, 4, and 6 hours, and were then analyzed 

 for non-protein nitrogen by the Macro-Kjeldahl method. As digestion progresses, 

 the proteins are broken down to non-protein nitrogen, a process by which the 

 proteins are so changed as to make assimilation possible. Therefore, an increase in 

 non-protein nitrogen indicates progress of digestion. By this method it was 

 found that digestion made the greatest progress during the first two hours and 

 increased only slightly from then on up to six hours. 



Preliminary results show that cocoa retards the digestion of the milk proteins 

 and this retardation is increased as the percentage of cocoa is increased from 1 to 

 4 percent in the milk. 



Bacteriological Study of Chocolate-Flavored Syrups and Cocoas. (R. L. 



France (Bacteriology) and W. S. Mueller.) The purpose of this investigation is 

 to find out to what extent chocolate-flavored syrups and cocoa powders are 

 responsible for microorganic contamination in chocolate milk. 



Twenty chocolate-flavored syrups and 20 cocoa powders have been analyzed 

 for total number and kind of microorganisms present. The plate count ranged 

 from 20 to 200,000 microorganisms per gram in the chocolate syrups and 1,000 

 to 55,000 microorganisms per gram in the cocoa powders. No coliform bacteria 

 or organisms producing hemoh'sis were found, which indicates the absence of 

 pathogenic organisms in the syrups and cocoas examined. Results to date in- 

 dicate that where the chocolate-flavored syrups are added to cold milk, some of 

 the syrups examined would seriously increase the bacterial content of the chocolate 

 milk. High bacterial counts in cocoa powders are not as serious as in chocolate- 

 flavored syrups, because the cocoa is heated during the preparation of the syrup 

 and also because less powder is used than syrup. 



The investigation will be continued until sufiicient samples have been an- 

 alyzed to draw more definite conclusions. 



The Effect of Aging Treatments on Gelatin and Other Ice Cream Stabilizers, 



(W. S. Mueller.) Various stabilizers have been subjected to the high initial aging 

 temperature treatment described for gelatin in last year's report. These substances 

 do not exhibit the differences in physical properties that were noted with gelatin. 

 Further studies are being made with other stabilizers. 



The effect of agitation during the high initial aging tempeiature period was 

 studied. The following treatments had a marked effect on the viscosity of a 

 1 percent gelatin solution. 



Viscosity 

 °M 



Aging 24 hrs. at 38° F., without agitation 134 . 7 



Aging 6 hrs. at 68° F. + 18 hrs. at 38° F., without agitation. . . . 304.5 

 Aging 6 hrs. at 68° F. with agitation + 18 hrs. at 38° F. without 



agitation 382 . 



These results indicate that the efficiency of gelatin in ice cream could be further 

 increased by agitating the mix during the initial high aging temperature period. 

 The effect of the amount of agitation during this period on various properties of 

 gelatin is being studied. 



