OZONE IN RELATION TO STORAGE OF APPLES 



13 



idly than the lower concentrations shown in experiment 2 (table 5) , but 

 the spore viability was very effectively reduced in all the tests when the 

 exposure w T as long enough. This finding substantiates the conclusion 

 of Ewell (S) that killing increases with concentration of the ozone 

 as well as with the time of exposure. 



Mold on Packages 



During the two storage seasons observations were made on mold 

 development on packages and on the storage-room walls. Veneer 

 boxes which had been wet before being placed in storage were very 

 susceptible to mold and in the control room many became covered with 

 extensive growth (fig. 5, B). Similar boxes in the ozonized room 

 appeared strikingly clean and free from mold (fig. 5, A). However, 



*m\ 



A 



Figure 5. 



-Apple boxes stored for 5 months at 31° F. : A, Exposed to 3.25 p. p. m. of 

 ozone; B, not exposed to ozone and showing abundant mold. 



upon examination after 5 months in storage a few small, black, in- 

 conspicuous mold colonies were found on some of the ozonized boxes. 

 To determine the viability of these established mold colonies, bits of 

 the mold were transferred to petri dishes containing nutrient agar. 

 Colonies of Penicillium grew from the transplantations, showing that 

 daily ozonization with an average concentration of 3.25 p. p. m. for a 

 period of 5 months had failed to kill the fungus. 



Two boxes from the control room having extensive mold growth 

 were placed in the ozonized room. After 16 weeks in the ozonized at- 

 mosphere, the mold was shrunk and dried and had become relatively 

 inconspicuous. Cultures demonstrated, however, that the mold was 

 still viable. 



These results are in agreement with those of Klotz (20), who found 

 that ozone only partially inhibited the germination and growth on 

 agar of the blue and green molds that cause penicillium rots of citrus 



