for different methods of storage (Sharples, 1980; Johnson, 1989). Ana-
lytical services were provided to growers, and advice was given on pre-
diction of bitter pit risk and management of consignments (Waller,
1980). Research was carried out to understand the influence of orchard
factors on the mineral composition of fruit, and of calcium in particu-
lar, that led to changes in orchard management practices to enhance cal-
cium uptake in the developing fruit.
Application of orchard sprays containing calcium is now routine in
U.K. orchards, and in most other apple-growing regions of the world.
Improved control of bitter pit has been achieved by changes in storage
technology, particularly the adoption of automated “ultra low oxygen”
(ULO) storage, and by prediction models that integrate climatic and nu-
tritional data that accounted for up to 67% of the variance in bitter pit
in air-stored Cox apples and 39% for similar samples stored in ULO
conditions (Johnson and Ridout, 1998). As a result of an integrated ap-
proach, bitter pit is now seldom a commercial problem in CA-stored
Cox apples in the U.K.
RESEARCH TO IMPROVE THE FIRMNESS
OF COX APPLES
Although changes in storage technology and the adoption of ULO
have improved the textural quality of Cox apples after storage (Sharples,
1982), variation in the firmness of consignments of apples removed from
store remains a significant problem. Regression models that predict the
firmness of Cox apples after CA storage, based predominantly on har-
vest firmness, have been developed from a three-year program of work
where storage behavior of apples from up to 32 orchards harvested over
a four-week period has been evaluated.
Figure 4.3 shows the relationship between harvest and ex-store firm-
ness for fruit harvested in 1994. Fitting a regression model based on har-
vest firmness only to data over a three-year period (1994–96) accounted
for 56% of the variation in ex-store firmness. Models that predict firm-
ness have also been developed from larger data sets, which include chem-
ical and physical measurements made on developing fruit in 24 orchards
over a six-year period. A number of models have been developed to pre-
dict the firmness of fruit from store. The inclusion of nutritional and cli-
matic variables with harvest firmness accounted for 76% of the variance
in the firmness values of CA-stored Cox apples (Johnson and Ridout,
1998). This research has prompted further investigation of the factors