546 
Journal of Agricultural Research 
Vol. XXVI, No. ii 
SUMMARY 
In determining the effect of the various factors on the feathering of 
cream in coffee, the acidity of the cream was taken as the basic factor, 
because it was present in all cases. It was also the factor having the 
greatest influence on feathering. Cream having an acidity of three- 
tenths of i per cent tastes sour to most people and will almost invariably 
feather when added to hot coffee. 
The average temperature of the coffee at the time of mixing it with the 
cream was about 95 ° C. 
The acidity of the coffee made by different processes, namely, boiled, 
percolated, and dripped, was practically identical. The hydrogen-ion 
determinations were respectively as follows: P H 4.92, 4.91 and 4.92. 
This excluded the method of preparation as having any effect on feather¬ 
ing. 
The acidity of coffee made by the drip method from high, medium, and 
low grades of known quality, and from a special brand of unknown quality 
but supposedly high grade, was practically the same. There was no 
noticeable difference in the effect of the various grades of coffee on the 
feathering of the cream. 
Each experiment consisted of— 
(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. 
Of these four factors, adding the coffee to the cream and sugar had the 
greatest effect on the feathering; in other words, the cream feathered at a 
much lower acidity in (d) than it did in either (a), (6), or ( c ). Adding 
the coffee to the cream without sugar, (c), had the least effect on the feath¬ 
ering, although the advantage as compared with (a) and (6) was very 
slight. 
Aging cream for from 7 to 10 days at a low temperature (i° or 2 0 C.) so 
as to keep acidity increase at a minimum, had no effect on the feathering. 
The richness of the cream had very little effect on the feathering, 
though the richer cream (higher in percentage of butterfat) feathered at a 
slightly lower acidity. This was undoubtedly due to the fact that the 
titratable acidity in the richer cream was more nearly true acid. 
Pasteurizing had but little effect on the feathering; however, there was a 
tendency for pasteurized cream to feather at a slightly lower acidity than 
the same cream not pasteurized. 
Homogenization greatly affected the feathering of cream, causing it to 
feather at a decidedly lower acidity than any of the creams not homog¬ 
enized. The greater the homogenizing pressure used, the lower the 
acidity at which the cream feathered. 
Freezing the cream had no effect on feathering. A heavy, oily layer 
always appeared on the coffee, however, when cream that had been 
frozen was added. 
The main factors causing feathering of cream in coffee are: High 
acidity; homogenization; adding hot coffee to cream and sugar. Acidity 
and homogenization are chiefly commercial problems. It is well to 
homogenize only cream of very low acidity if it is to be used in coffee, 
and to keep the homogenizing pressure as low as possible. Adding hot 
coffee to cream and sugar is a household and restaurant problem. It is 
well not to mix the cream and sugar before adding the hot coffee. 
