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Circular No. 765 



January 1948 • Washington, D. C. 



UNITED STATES DEPARTMENT OF AGRICULTURE 



Ozone in Relation to Storage of Apples 



By H. A. Schomer, associate physiologist, and L. P. McColloch, associate plant 

 pathologist, Division of Fruit and Vegetable Crops and Diseases, Bureau of 

 Plant Industry, Soils, and Agricultural Engineering, Agricultural Research 

 Administration 1 



CONTENTS 



Page 

 Evaluation of ozone in apple 



storage 1 



Materials and methods 4 



Storage facilities and fruit 4 



Ozonizer 4 



Method of analysis 6 



Effect of ozone on fungus spores 7 



Spores on glass-slide cultures- 7 

 Natural spore load of storage- 

 room air 8 



Spore load introduced in air of 



empty storage room 10 



Mold on packages 13 



Effect of ozone on the develop- 

 ment of fruit decay 14 



Fruit inoculated with Penicil- 



lium expansum 14 



Page 

 Effect of ozone on the develop- 

 ment of fruit decay — Con- 

 tinued 

 Fruit inoculated with Phialo- 



phora malorum L 16" 



Fruit in the regular pack 17 



Effect of ozone on development 



of scald 18 



Effect of ozone on quality of 



fruit 19 



Ozone injury 19 



Flavor - 21 



Appearance 21 



Physiological properties 22 



Summary 23 



Literature cited 23 



^ ^^^^^ *^ ^» " i ^ 



EVALUATION OF OZONE IN APPLE STORAGE 



Ozone is generally used as a supplement to refrigeration in the 

 commercial storage of eggs, because it is a deodorizer and a deterrent 

 to surface molds which develop in the high humidities required. It 

 is not widely used in the cold storage of apples and other fruits, but a 

 few commercial storages employ it regularly. 



The properties of ozone that make it desirable are its powerful 

 oxidizing action, its pleasant odor in very dilute concentrations, and 



1 Acknowledgment is made to C. O, Bratley and J. S. Wiant, Division of Fruit 

 and Vegetable Crops and Diseases, for their assistance ; to Max Phillips, Pro- 

 duction and Marketing Administration, for the use of an ozonizer during part 

 of the investigation ; and to the Merchants Refrigerating Co., New York, N. Y., 

 the Manhattan Refrigerating Co., New York, N. Y., the Merchants Cold Storage 

 and Warehouse Co., Providence, R. I., and the Hygeia Refrigerating Co., Elmira, 

 N. Y., for their cooperation. 



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