UNITED STATES DEPARTMENT OF AGRICULTURE 



JVi^^^t- 



I 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 coohng 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 pa])er wo shall give the results of this work. 

 As additional information, some data o.n the reverse process — the 

 heating of cold bottled milk by means of circulated hot air — will also 

 }>e given, 



' Ayers, 8. ITenry, and Johnson, W. T., jr., Pasleurizing Milk in Bottles and BottliriR Hot Milk I'as- 

 tcurizerl In Hulk. Bulletin 210, U. 8. Department of Agriculture, Also in Jour, of Infec. Dis., vol. 14j 

 .N'o. 2, March, lOH, pp. 217-211. 



.5.5377°— Bull. 42'>— 16 1 



