Nov. 15, 1919 Nature and Control of Apple-Scald 217 



atable if held in storage with other food products. In view of these 

 facts there seems to be Httle doubt that the beneficial effects of the fats 

 and oils in the wrappers are due to the absorption of esters or similar 

 products thrown off by the apple. The hypothesis is given further sup- 

 port by the fact that the fats and oils which are known to have a great 

 absorbing power for gases give more complete control of scald than 

 paraffin and similar waxes that are generally recognized as being more 

 inactive toward these gases, and also by the results in the experiments 

 reported above in which scald was produced artificially by exposing 

 apples to various esters. 



It is generally recognized in the apple trade that greasy, waxy apples 

 do not scald as soon or as badly as the others. The above hypothesis 

 offers a possible explanation for this fact, the wax of the apple, like that 

 in the wrapper, apparently serving as an absorbent for the harmful gases. 



TISSUES AFFECTED BY APPLE-SCAI,D 



Scald is typically a skin disease of the apple. In the early and more 

 typical stages of the trouble, only the five or six surface layers of cells 

 that form the color-bearing tissue of the apple are affected. With long 

 continued unfavorable conditions the apple tissue may become dead, 

 brown, and rotlike to a depth oi yito% inch, and occasionally the disease 

 spreads practically to the core. Reference is made here to the scald itself ; 

 but with the death of the protective skin layer, various rot organisms have 

 free access to the softer tissues beneath and usually play an important part 

 in hastening the destruction of the apple. Not all portions of the skin 

 are equally susceptible to scald. The highly colored areas of red apples 

 are affected only in the most extreme cases of scald. Often when the 

 poorly colored areas are badly and deeply scalded, the diseased condition 

 will shade off into a mere brown tint of the skin as the margin of the 

 blush area is approached. The chemical changes that occur in the 

 reddening of the fruit apparently produce a skin condition that is highly 

 resistant to scald. 



The statement is quite generally current that apples that still show 

 the leaf green are very much more susceptible to scald than those which 

 have become slightly yellowed. As a rough statement of the facts, this 

 may be approximately true. The observations of the writers, however, 

 indicate that while green apples, in general, are more susceptible to scald 

 than ripe ones, those still having the leaf green are very much less sus- 

 ceptible than those that have just begun to turn yellow, and often less 

 susceptible than those in which the ground color has become a deep 

 yellow. They have also observed that while green apples may finally 

 become more severely scalded than riper ones, the latter usually scald 

 first if they develop the disease at all. In spite of these qualifications, it 

 is still true that scald can be greatly reduced and delayed by leaving the 

 apples on the tree till well matured. 



