200 



Journal of Agricultural Research 



Vol. XVI, No. 8 



of 85 to 95 per cent and an air movement of >^ to X "lile per hour. With 

 two exceptions, both in the case of very green apples at 0°, the fruit 

 held in the open remained free from scald to the end of the various experi- 

 ments, indicating that other factors are even more important than tem- 

 perature, and that a solution of the problem of scald prevention should 

 be found^either in the composition or rate of movement of the storage 



air. 



INFLUENCE OF AIR COMPOSITION UPON APPLE-SCALD 



HUMIDITY 



It did not seem probable that a reduction in the relative humidity 

 from 100 per cent to an average of 90 per cent as mentioned above 

 could be responsible for the complete elimination of scald, but it 



seemed desirable to 

 have further tests on 

 the point. Table III 

 gives the results of va- 

 rious experiments in 

 which the humidity was 

 varied, with little or no 

 change in temperature 

 or other environmental 

 factors. In cases where 

 it was necessary to in- 

 troduce outside air this 

 was brought to the tem- 

 perature of the fruit 

 before being allowed to 

 come in contact with it. 

 A study of the results 

 from the various experi- 

 ments reported in Table 

 III shows that, in gen- 

 eral, only about half as 

 much scald developed 

 on apples exposed to dry air as on those exposed to saturated air. It does 

 not seem, however, that high humidity can be the primary cause of the 

 disease, for in no case was scald entirely prevented by dryness, and in 

 every case where the air was stirred, the disease was practically eliminated, 

 even in the presence of the highest humidities. The withering of the 

 apples in the dry air makes this method of partial prevention an imprac- 

 tical one, and the fact that the disease can be prevented without drying 

 naturally raises the question whether the beneficial efifects noted from 

 the use of moisture-absorbing agents may not be at least partly due to 

 their power to absorb some substance other than water, or to the fact 

 that the evaporation of the water assists in the elimination of some dis- 

 tinctly harmful substance. 



Fig. 4. — Graphs showing the effects of temperature on apple-scald 

 at the end of 2, 3, 4, 5, 7, 12. and 16 weeks. The dotted graphs show 

 the amount of scald that was evident after removal from storage 

 at the end of the given week and holding the apples at 20° C. for 

 3 days. The apples were from the same trees as those of figure 3, 

 but were picked 24 days later, on September 13, and the experiment 

 was started on September 14. 



