Post-Storage Scald Development 



One of the concerns about scald is that while it 

 may not appear on fruit on removal from storage or 

 when packed, it may appear later, before fruit are 

 consumed. We had not intended to address this issue, 

 but we would like to report here that we did not see a 

 great deal of scald developing during the week the fruit 

 were kept at room temperature. In 1996 and 1997, we 

 inspected some of the fruit at the time of removal from 

 storage, as well as after 7 days at room temperature. 

 Figure 4 shows that on air-stored Delicious, this post- 

 storage increase in scald was not significant. Note that 

 sometimes more scald was discernible at removal from 

 storage than after a week at room temperature. This is 

 an indication of the difficulty we sometimes had in 

 determining if fruit discoloration was or was not scald. 

 It should be made clear that not all cultivars are like 

 Delicious in this regard. For example, we have 

 observed repeatedly that Cortland may show little or 

 no sign of scald at removal from storage, but after 7 

 days at room temperature, much scald is present. 



Conclusions 



We conclude from this research that forecasting 

 scald susceptibility on air-stored New England 

 Delicious is feasible, and we believe that use of these 

 prediction models can lead to more efficient use of 

 DPA. Results of 3 years of tests of the models 

 developed from 6 previous years' data indicate that 

 using a calendar, a min-max thermometer, and a starch 

 test for maturity, one can use these equations to 

 effectively predict high, intermediate, or low scald 

 susceptibility of Delicious apples harvested at a given 



site on a given day anywhere in New England. 

 Furthermore, the equations predict the need for DPA: 

 highly susceptible fruit require 2000 ppm, intermedi- 

 ately susceptible fruit require only 500 ppm, and low- 

 susceptibility fruit, particularly those with an Index 

 greater than 1 in Equation 2, have no need for DPA 

 treatment. We offer a system for determining which 

 fruit need 2000 ppm DPA, which will be protected by 

 500 ppm, and which may be stored without DPA 

 treatment, and with a minimum of concern for post- 

 storage scald development on air-stored fruit. As 

 demonstrated by the data in Tables 1 and 2, it is 

 possible to choose an Index higher than zero in 

 Equation 2 as a demarcation between groups of fruit 

 which receive 500 ppm DPA and those which receive 

 none. This can be especially useful if experience has 

 shown that the fruit from particular trees are especially 

 scald susceptible, and allows flexibility in determining 

 at what point to stop applying DPA. 



Acknowledgments 



The authors would like to thank the following 

 people for their assistance in selection and provision of 

 fruit and preharvest information for developing and 

 testing scald prediction models: Dana Clark, Evan 

 Darrow, David Kollas, William G. Lord, Wayne Rice, 

 James Schupp, Joe Sincuk, Tim Smith, and Mark and 

 Bob Tuttle. Technical assistance by Irene Clark and 

 Laura Lee Jones is much appreciated. We would also 

 like to thank the Massachusetts Fruit Growers' 

 Association, the New England Tree Fruit Growers 

 Research Committee, and the Washington Tree Fruit 

 Research Commission for their financial support of 

 this research. 



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Fruit Notes, Volume 63 (Number 3), Summer, 1998 



