assessing maturity. 



In 1988, the Mcintosh starch chart was used 

 to assess starch loss from Liberty. The begin- 

 ning of optimal harvest was when the starch 

 index level reached 3-3.5. In 1989, because of a 

 better match of the pattern, the Empire chart 

 was used for Liberty fruit. Optimal harvest was 

 when the starch index value reached 4.5. In 

 1990, a chart specific to Liberty was developed. 

 This chart has been roughly calibrated with 

 informal taste evaluations, and under Massa- 

 chusetts conditions, harvest of Liberty fruit 

 should begin when the starch index value 

 reaches 4.5. (The Liberty chart is available from 

 Wesley R. Autio, 205 Bowditch Hall, University 

 of Massachusetts, Amherst, MA 01003, at a cost 

 of $ 1 per copy. Subscribers to the Massachusetts 

 Extension Fruit Newsletter will receive a copy of 

 the chart with their subscriptions.) 



Storage Studies 



For storage studies, the same trees as in the 

 harvest-season studies were used. In 1988, 

 apples were harvested from each block at 

 weekly intervals beginning on September 20 

 and ending on October 1 1. Flesh firmness was 

 measured at harvest and after storage at 32°F 

 until December 14. The firmness of Liberty and 

 Empire fruit were not significantly different; 

 however, there were differences among the four 

 harvest dates. Fruit from the three later dates 

 softened to a lesser degree than those from the 

 September 20 harvest. 



In 1989, apples were harvested from each 

 block on September 22 and 29 and October 6. 

 Flesh firmness was measured at harvest and 

 after four months of storage at 32°F. Liberty 

 fruit softened to a lesser degree during storage 

 than Empire fruit, and those from the latest 

 harvest softened more than those from the ear- 

 liest harvest. 



After storage, the fruit were kept at 70°F for 

 14 days, after which the incidences of storage 

 disorders were assessed. Decay, bitter pit, and 

 senescent breakdown were more prevalent in 

 Empire fruit than Liberty fruit. Browncore, on 

 the other hand, was much more of a problem 

 with Liberty than Empire. Browncore was 

 present in between 70 and 90% of the Liberty 



fruit after four months at 32°F and 14 days at 

 70°F. 



Considering firmness, bitter pit, decay, and 

 senescent breakdown, Liberty fruit had supe- 

 rior storage quality to that of Empire fruit; 

 however, the incidence of browncore must be 

 seen as a significant detractor. Browncore is a 

 sign of chilling sensitivity, and the high inci- 

 dence of browncore in Liberty suggests that it is 

 a very chilling-sensitive cultivar and cannot be 

 kept at 32°F for extended periods of time. 



To maximize the length of the marketing 

 period many growers keep apples for extended 

 periods under controlled atmospheric condi- 

 tions. The two types of storage used most 

 commonly in New England are "hard CA" (32°F, 

 -3% 2 , and <2% C0 2 ) and "soft CA" (38°F, 3% 

 2 , and 5% C0 2 ). Generally, cultivars which are 

 chilling sensitive are kept in soft CA, and those 

 that are chilling resistant are kept in hard CA 

 To determine the best type of storage conditions 

 for Liberty, fruit from the 1988 harvest were 

 kept in hard or soft C A for 5 or 6. 5 months. After 

 storage the flesh firmness was measured, and 

 there was no difference between Liberty and 

 Empire; however, both cultivars softened less in 

 soft CA than in hard CA. The 1989 harvest was 

 kept under conditions similar to those of 1 988 for 

 5.5 months. Less softening occurred during 

 hard CA than soft CA storage. Significant 

 amounts of senescent breakdown developed 

 only in Liberty fruit after hard CA storage. 

 Significant amounts of bitter pit developed in 

 Empire fruit only after soft CA storage, and 

 significant amounts of browncore developed in 

 Liberty fruit in both types of CA storage. 



It is clear from these results that Liberty 

 fruit can develop a great deal of browncore in 

 standard controlled atmosphere storages. It 

 was surprising to observe large amounts of 

 browncore even in the soft CA storage, where 

 the temperature was at a level which usually 

 precludes the development of browncore. When 

 a very chilling-sensitive cultivar is kept for ex- 

 tended periods, however, it may be necessary to 

 utilize an even higher temperature than 38°F. 

 Further work must be done to identify a usable 

 temperature for long-term storage of Liberty 

 fruit. 



Fruit Notes, Summer, 1991 



19 



