CHEMICAL CHANGES ACCOMPANYING THE DECAY OF PEACHES 



BY MONILIA. 



In seasons of heavy crops there are available large quantities of 

 sound, overripe peaches which it will not pay to market as fresh 

 fruit. Particularly is this the case when hot weather causes the 

 fruit to ripen rapidly. It is anticipated that the great bulk of peach 

 vinegar will be made from such fruit, which, while too ripe to ship, is 

 otherwise essentially sound. As before stated, notes were taken 

 when the samples of peaches were ground as to the extent of infec- 

 tion by Monilia, and it was found that the alcoholic fermentation 

 was not perceptibly influenced. Two special experiments were 

 undertaken to determine how the presence of a large proportion of 

 rot would affect the value of peaches as vinegar-making material. 

 In each, using Mountain Rose and Elberta, respectively, about a 

 carrier of peaches was inoculated with a pure culture of Monilia by 

 Mr. W. M. Scott, pathologist in the Bureau of Plant Industry, and 

 the fruit was allowed to decay for eleven and for ten days. After 

 the sample had thoroughly rotted the fruit was ground, pressed, and 

 the juices analyzed. The composition of these juices is shown in 

 Table 7, contrasted with the analyses of juices from sound fruit of 

 the same lots. The most conspicuous changes were the inversion of 

 sucrose and the loss in total sugars. The inversion of the cane 

 sugar was nearly complete, and the losses in total sugars amounted 

 to 1.18 and 2.47 per cent or to 11.7 and 25.6 per cent of the total 

 sugar in the juices of the sound peaches. Small quantities of alcohol 

 and acetic acid were also formed, probably as a result of fermentation 

 by yeasts and bacteria. 



TABLE 7. Changes in peach juice due to decay by Monilia. 



Samples of vinegar made in the field from peaches rotted in cribs 

 have been examined by the writer. The juice liberated during decay 

 was collected in barrels and allowed to go to vinegar. These vine- 

 gars were generally deficient in acid, many had disagreeable flavors 

 and after-tastes, and they darkened rapidly on exposure to the 

 air. Obviously, vinegars should not be made from peaches of this 

 character. 



[Cir. 51] 



