- 3 - 



Because of some observations in other experiments with calcium 

 on apples, Dr. Mack Drake sampledsome of these apples from orchards 

 that produced fruit of different degrees of softening and analyzed 

 them for calcium. The results of these observations were as follows: 



Average firmness 5/9/74 



of fruit (lbs) 8.2 9.7 10.9 11.8 13.0 13.0 13.2 



Peel calcium (ppm) : 309 393 327 374 486 608 692 



As can be seen, the firmest fruit had twice the amount of calcium 

 in them as the softest fruit. There was a significant correlation 

 between calcium level and firmness; that is, the higher the calcium, 

 the firmer the fruit. However, this represents a very limited num- 

 ber of observations. To obtain additional evidence on this rela- 

 tionship, in May, 1974, fruit of comparable size but clearly differ- 

 ent condition were taken from identical boxes of Mcintosh that had 

 been grown and stored at the Research Center. When analyzed for 

 calcium, we found the following: 



Fruit condition: Split Soft Firm 

 Peel calcium, ppm: 484 516 606 



The firm fruit had a significantly higher calcium level than the 

 split or soft fruit. Thus, there is limited evidence that a low 

 calcium level may be contributing significantly to the "soft Mac 

 problem." 



What, then, is the "soft Mac problem?" It is our present be- 

 lief that it is not a unique problem, but rather an expression of 

 rapid aging and deterioration of the apples. We have noted that 

 these "soft Macs" usually show symptoms of senescent browning in 

 their flesh. This aging could be promoted by any or all of the 

 factors cited by Smock. Furthermore, the correlation of weather 

 and softening, noted by Blanpied and Smock, and our correlation 

 between calcium and softening could be related and contributing 

 to aging. Dry weather impedes absorption of calcium by tree rooots, 

 and so the water stress may be reducing calcium level. Subsequent 

 rain may aggravate this problem by promoting rapid growth, and hot 

 weather may advance maturity. Both low calcium and advanced matur- 

 ity can hasten deterioration during storage. In this way, all that 

 we know about causes of "soft Macs" can be related, and this rela- 

 tionship corresponds to our observations. Time will tell whether 

 or not this view is correct, but for now it serves as our best model 

 for understanding the problem. 



