22 
LABORATORY MANUAL 
EXERCISE NO. 14 
Object: To become acquainted with the proper method of obtaining and test¬ 
ing a composite sample of milk. 
Procedure: A composite sample of milk or cream is a mixture of each 
weighing of milk, taken in such a manner that it shall be pro¬ 
portional to the total weight of milk or cream tested. 
A. Test separately each of the three samples of milk provided, 
which were taken from lots of milk weighing 200, 300, and 400 
pounds respectively. Calculate the true average test of the 
samples of milk according to F. & W. f 196, 197, 198. 
B. Take an equal sample (one pipetteful) from each lot of milk, 
mix thoroughly and test in duplicate. 
C. Take a correct composite sample (2 pipettefuls from the 200 
pound lot, 3 pipettefuls from the 300 pound lot, etc.) mix 
thoroughly and test in duplicate. 
Observations: 
Sample 
% fat 
Average 
Color 
Condition 
1 
a 
b 
c 
2 
a 
b 
3 
a 
b 
Conclusion: 
Questions: (1) Give a brief description of six different appliances used 
for obtaining a composite sample of milk. 
(2) Name the preservatives commonly used for composite samples 
of milk. 
(3) Why is it not advisable to practce composite sampling and 
testing of cream in creameries? 
(4) Describe in detail how composite samples should be cared for. 
References: F. & W. If 179-199 inclusive; Van S. pp. 24-31; Jud. pp. 
46-58; St. pp. 109-112, 122. 
