PREDICTING THE KEEPING QUALITY OF MCINTOSH APPLES 

 FROM PREHARVEST MINERAL ANALYSES OF FRUIT 



William J. Bramlage, Sarah A. Weis, and Mack Drake 

 Department of Plant and Soil Sciences 



If the storage potential of apples could be predicted accurately at 

 harvest, the fruit could be stored and marketed within these potentials. 

 Lots of fruit with potential for long-term storage could be stored long- 

 term, ones whose potential is not as good could be marketed in early- to 

 mid-winter, and ones with little storage potential could be marketed in the 

 fall. In this way the grower could make maximum use of his fruit and the 

 consumer could benefit by purchase of better quality fruit. 



During the past 30 years a large volume of research has established 

 that mineral compostion is related to keeping quality of apples by 

 influencing the onset and rate of ripening, but especially by determining 

 the occurrence of physiological disorders after harvest. Early research 

 focused primarily on bitterpit, which is caused by a deficiency of calcium 

 (Ca) in the fruit, but it is now recognized that many apple disorders are 

 influenced, if not caused, by adverse mineral compostion of the fruit. 



The predictability of storage disorders from preharvest mineral 

 analyses was first proposed in England; methods of fruit analyses and pre- 

 diction from the results were then developed there. For a number of years, 

 a large cooperative storage (East Kent Packers, Faversham, Kent) has used 

 predictions from fruit mineral analyses to schedule storage withdrawals for 

 its Cox's Orange Pippin apples. Since value of the apples generally 

 increases with later marketing, growers who maintain proper mineral levels 

 in their fruit are rewarded by later marketing of their fruit and the 

 corresponding higher prices paid for them. 



During the 4 years 1979 to 198?, we conducted extensive surveys to 

 determine (1) the effects of minerals in Massachusetts-grown Mcintosh apples 

 at harvest on their keeping quality; and (2) if it is possible to predict 

 the keeping quality of our apples from preharvest mineral analyses. Our 

 findings in regard to the first question have been reported earlier ( Fruit 

 Notes 48(4) :4-8), and can be summarized in one sentence: "...inadequate Ca 

 in fruit is the primary nutritional factor influencing quality of Mcintosh 

 apples in Massachusetts, and this factor is expressed mostly in the 

 occurrence of breakdown after storage." We found that many orchards were 

 producing Ca-deficient fruit which therefore possessed lessened potential 

 for long-term storage. Here we now report our findings about predictability 

 of keeping quality from mineral analyses. 



We used 2 different approaches to prediction. First, we used a scoring 

 system similar to the one developed in England, which gives each sample a 

 "score" for its mineral composition, and this score is then used to predict 

 the keeping quality of the fruit. The score is based on the concentrations 

 of N, P, K, Ca, and Mg in the fruit 2 weeks before harvest. A preliminary 

 report ( Proceedings of the Massachussetts Fruit Growers Association 

 88:46-56) concluded that a prediction based on such a score was feasible for 

 our apples, but also that accuracy of the prediction was quite variable. 



