UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 420 
Contribution from the Bureau of Animal Industry 
A. D. MELVIN, Chief 
Washington, D. C. 
PROFESSIONAL PAPER 
October 27, 1916 
COOLING HOT-BOTTLED PASTEURIZED MILK BY 
FORCED AIR. 
By S. Henry Ayers, John T. Bowen, and W. T. Johnson, Jr., 
Dairy Division, Bureau of Animal Industry. 
CONTENTS. 
Introduction 1 
Description of experimental apparatus 2 
Description of instruments and method of re- 
cording data 3 
Relative rate of cooling of milk and water ... 5 
Relative rate of cooling with still air and 
forced air 5 
Results of cooling by means of forced air 9 
Temperature variations in quart bottles of 
milk and water under varying conditions. . 19 
Cost of cooling by means of cold outside air. . . 23 
Effect of slow cooling on the bacterial flora of 
milk after pasteurization _ . 26 
Effect of the process on the cream line and 
flavor of milk 30 
Experiments in heating bottled milk by 
forced air 32 
General summary 35 
Conclusion 37 
INTRODUCTION. 
Since 1912 the process of cooling hot bottled milk by means of 
forced-air draft has been studied in the Dairy Division of the Bureau 
of Animal Industry. The first experiments, which were conducted 
on a laboratory scale, indicated that forced-air circulation might be 
successfully used for cooling hot pasteurized milk in bottles. The 
results of that investigation * indicate the probable means by which 
the method could be used on a commercial scale. It was realized 
that laboratory and commercial conditions are essentially different, 
and in consequence cooling experiments on a 30-crate basis were 
started in 1913. In this paper we shall give the results of this work. 
As additional information, some data on the reverse process — the 
heating of cold bottled milk by means of circulated hot air — will also 
be given. 
i Ayers, S. Henry, and Johnson, W. T., jr., Pasteurizing Milk in Bottles and Bottling Hot Milk Pas- 
teurized in Bulk. Bulletin 240, U. S. Department of Agriculture. Also in Jour, of Infec. Dis., vol. 14. 
No. 2, March, 1914, pp. 217-241. 
55377°— Bull. 420—16 1 
