UNITED STATES DEPARTMENT OF AGRICULTURE 



Jl BULLETIN No. 916 



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Contribution from the Bureaa of Plant Industry 

 WM. A. TAYLOR, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



June 13, 1921 



FREEZING INJURY TO POTATOES WHEN 

 UNDERCOOLED. 1 



By R. C. Weight, Physiologist, and George F. Taylor, Chemical Laboratorian, 

 Office of Horticultural and Pomological Investigations. 



CONTENTS. 



Scope of the investigations 



Physiology of the freezing process. 

 Plan of the work 



Page. 

 1 



Page. 

 Inoculation of undercooled potatoes- 7 



Summary 14 



Literature cited 15 



SCOPE OF THE INVESTIGATIONS. 



Each year the loss to growers, shippers, and carriers of potatoes 

 due to freezing reaches an enormous figure. This is particularly 

 true of the late or main crop produced in the Northern States. This 

 crop is usually in constant danger of exposure to freezing tempera- 

 ture from just before it is harvested until it reaches the consumer. 

 There are two general classes of frost-injured potatoes — those frozen 

 solid and subject to collapse immediately on thawing and those that 

 show evidence of injury only on being cut open a few hours after 

 being warmed. The first class of injured potatoes is easily identified 

 by the soft, wet condition that develops on thawing. This type of 

 injury is due to the potato being subjected to freezing at very low 

 temperatures or to prolonged exposure at higher freezing tempera- 

 tures. The second type of injury is not apparent on superficial ex- 

 amination. It is due to exposure to temperatures just below the 

 freezing point or to a very low temperature for a short time. If after 

 the potato has been thawed a few hours it is cut open, evidences of 

 this type of freezing injury are apparent by the presence of vascular 

 discoloration of three types or a combination of any of the three. 



1 This bulletin gives the results of a portion of the work carried on under the project 

 " Factors affecting the storage life of vegetables." 

 11310°— 21 



