OZONE IN RELATION TO STORAGE OF APPLES 3 



the ozonized atmosphere, so that the viable scores occurring naturally 

 in the atmosphere were reduced to an insignificant number. Accom- 

 panying this lethal effect was the absence of mold development on the 

 surfaces of packages and on storage-room walls. Boxes became moldy 

 in the humid storage room in which the atmosphere was not ozonized 

 (check lot) , but no mold appeared on boxes in the ozonized atmosphere. 



This effect of ozone makes it highly desirable in egg storage, for 

 which a very high humidity is desired. Molds develop readily on 

 the surfaces of the crates and of the eggs under such conditions, but 

 ozone retards the mold development. 



In spite of its control of surface mold, however, ozone failed to kill 

 fungus colonies on the surface of packages when they had become 

 established before ozonization. Although these colonies appeared 

 to be dead and were inconspicuous as a result of ozonization, they 

 were still viable after several months' exposure to the ozonized 

 atmosphere. 



Furthermore, exposure of apples for an entire storage season of 7 

 months to an atmosphere containing 3.25 p. p. m. of ozone failed 

 to check decay. In a number of instances infection of inoculated 

 fruit was even greater in the ozonized than in the nonozonized lots. 

 This was thought to be due to further injury of the wounded tissue 

 by ozone, which predisposed it to fungus invasion. It appears that 

 the rapid interaction of ozone with organic matter prevents its pene- 

 tration below the surface of the substrate, so that fungi protected by 

 fruit tissue, as in fruit inoculated naturally or artificially, are not 

 killed by ozone although their rate of growth is retarded. 



Since apple scald is caused by volatile emanations from the fruit 

 and ozone oxidizes organic substances with unsaturated bonds, such 

 as ethylene, observations were made on the effect of ozone on scald 

 development in Arkansas (Mammoth Black Twig) apples, a variety 

 very susceptible to the disorder. Scald development was reduced 

 appreciably by the ozone, but not sufficiently to afford satisfactory 

 control. 



At the concentration of 3.25 p. p. m., injury due to ozone occurred 

 on every variety in storage. It appeared as brown sunken areas at 

 the lenticels, the intensity varying with the variety. Golden Delicious 

 was the most sensitive of the varieties used in the experiment, whereas 

 the injuries occurring on Winesap and Delicious were hardly objec- 

 tionable. Borne Beauty apples were injured by a single exposure 

 when they were in a storage room in which the ozonizer was operated 

 2% hours and produced an ozone concentration of 33.9 p. p. m. The 

 apples were not removed from the room after the generator was turned 

 off, and the injury appeared within a few days. 



In addition to injury of lenticel tissue, there were other serious 

 effects of extended exposure to 3.25 p. p. m. of ozone. The surface 

 (skin) of some varieties became sticky and varnishlike in appearance. 

 The flavor of the fruit (except Golden Delicious) was impaired, the 

 extent of the off-flavor varying with the variety. Previously, in a 

 survey of several large commercial cold storages in the East, there 

 were found a number of operators who refused to use ozone in apple 

 storage for fear of impairing the flavor of the fruit, but no reference 

 was found in the literature to support their contention. During 

 this study the objectionable effects on flavor resulted from 7 months 



