Dec. 15,1923 
543 
Feathering of Cream in Coffee 
(a) Adding cream to coffee without sugar. 
(b) Adding cream to coffee and sugar. 
(c) Adding coffee to cream without sugar. 
(d) Adding coffee to cream and sugar. 
Cream always feathered at a lower acidity in method (d)—when the 
coffee was added to the cream and sugar. (See Tables III to VIII.) This 
may be attributed to the fact that the sugar in dissolving used moisture 
from the cream and in so doing precipitated some of the casein present, 
causing feathering when the hot coffee was added. If the sugar was 
moistened with a little water before adding the cream, or the sugar was 
added to the coffee either before or after adding the cream, then the 
sugar had no effect on the feathering. 
In practically all the tests, method (c )—adding the coffee to the cream 
without sugar—had the least effect on the feathering, i. e., the cream did 
not feather at so low an acidity when the coffee was added to the cream 
without sugar. Sugar may be added afterwards without affecting the 
feathering. (See Tables III to VIII.) 
AGE OF CREAM 
The effect of age of cream on feathering was determined by aging cream 
at low temperatures (i° to 2 0 C.) so as to keep acidity increase at a mini¬ 
mum. Aging cream for 7 to 10 days by this method had no effect on the 
feathering. 
KIND OF CREAM 
The richness of the cream had very little effect on the feathering. The 
richer creams, i. e., those containing a higher percentage of butterfat, 
feathered at a slightly lower acidity. This was undoubtedly due to the 
fact that the acidity in the richer creams was more nearly true acid than 
in the case of the less rich creams, containing more solids not fat, which 
would affect the titratable acidity. (See Tables III and IV.) 
The acidity of all the cream was determined by titrating 10 cc. of 
the cream with N/20 NaOH, using phenolphthalein as indicator. 
Pasteurizing had but slight effect on the feathering. Comparative 
tests of raw and pasteurized creams showed that the pasteurized creams 
feathered at a slightly lower acidity than the same cream not pasteurized. 
(See Tables III, V, and VI.) 
Homogenizing greatly affects the feathering of cream. Homogenized 
cream feathered at a decidedly lower acidity than any that was not 
homogenized. There were considerable variations in the percentage of 
acidity at which the homogenized cream feathered, due undoubtedly to 
the fact that the samples were purchased from different dealers, who 
probably were using different homogenizing pressures. No information 
concerning the pressures used was obtained. (See Table VII.) Com¬ 
parative tests, using different pressures, showed that the higher the pres¬ 
sure at which the cream was homogenized, the lower the acidity at which 
it feathered. (See Table VIII.) 
Freezing the cream had apparently no effect on the feathering; a heavy 
oily layer would form on the coffee, however. 
RESULTS OF EXPERIMENTS 
In Tables III to VIII, showing the results of the experimental work, 
the four methods of mixing the cream and coffee are described as follows: 
a represents adding cream to coffee without sugar; b represents adding 
