The Liberty Apple: Ripening and 

 Storage Properties 



Wesley R. Autio 



Department of Plant & Soil Sciences, University of Massachusetts 



Joseph F. Costante 



Department of Plant & Soil Science, University of Vermont 



Environmental and food safety concerns 

 about the use of pesticides to maintain the 

 production of high quality apples have resulted 

 in a great deal of research with the goal of 

 reducing pesticide applications. Additionally, a 

 significant breeding effort has been underway 

 for a number of years to produce apple cultivars 

 which are resistant to the major fruit diseases. 

 One such cultivar, Liberty, was bred at the New 

 York State Agricultural Experiment Station in 

 Geneva and was released in 1978. Liberty is 

 resistant to apple scab, cedar apple rust, fire 

 blight, and powdery mildew. Because of its 

 quality and the heightened concerns about pes- 

 ticide use, New England growers have become 

 very interested in Liberty as a commercial cul- 

 tivar. In fact, a recent survey suggested that it 

 would be the fifth most planted cultivar in New 

 England through the first half of the 1990's, a 

 remarkable achievement for a cultivar that was 

 not planted at all in the first half of the 1980's. 



Unfortunately, very little information is 

 available about the horticultural characteris- 

 tics of Liberty, and very importantly, little is 

 known about the ripening and storability of the 

 fruit. The objective of the work reported here 

 was to obtain some baseline information about 

 Liberty ripening and how best to store the fruit. 



Harvest-season Changes 



For maturity studies in 1988-90, Liberty/ 

 M.7A trees planted in 1980, and Empire/M.26 

 trees planted in 1975 at the University of Mas- 

 sachusetts Horticultural Research Center 

 (HRC), Belchertown, were used. 



Each year, harvests were made periodically 



throughout the harvest season. The internal 

 ethylene concentration of each fruit was mea- 

 sured, the percent surface red color of each fruit 

 was assessed, the weight was determined, flesh 

 firmness was measured, and the soluble solids 

 (sugar) content was evaluated. Fruit were also 

 cut equatorially, dipped in an iodine-potassium 

 iodide solution, and rated for starch loss. 



Figures 1 through 3 depict how quality and 

 ripening of Liberty and Empire fruit changed 

 during the harvest season. Generally, Liberty 

 fruit were smaller than Empire fruit, but this 

 difference likely was related to crop load. When 

 the firmness difference was significant, Liberty 

 fruit were firmer than Empire fruit during the 

 harvest season, even after the effects of fruit 

 weight were removed. In most years, the soluble 

 solids content of Liberty fruit was higher than 

 that of Empire fruit, and Liberty fruit generally 

 were more highly colored than Empire. 



Informal taste evaluations suggested that 

 the appropriate beginning date of harvest for 

 these two cultivars was similar, September 30, 

 approximately one week before Delicious; how- 

 ever, measurement of internal ethylene concen- 

 trations showed that Liberty is a peculiar culti- 

 var, in that internal ethylene levels exceeded 

 one ppm (the normal level associated with the 

 initiation of ripening) as much as two weeks 

 prior to the apparent optimal beginning date of 

 harvest. It seems unlikely that Liberty fruit 

 should be harvested that early. The problem 

 with this situation is that it makes accurate 

 assessment of fruit ripening very difficult, since 

 a rise in ethylene content is normally considered 

 to be the signal that ripening has begun. Alter- 

 natively, the starch-iodine test may be helpful in 



Fruit Notes, Summer, 1991 



15 



