ered more fully later. Briefly, to achieve consistent quality from store,
full account must be taken of the considerable variation in quality at-
tributes and the physiological state of the fruit at the time of harvest.
VARIABILITY IN QUALITY PARAMETERS
AFTER STORAGE
Apples that are destined for long-term CA storage are normally har-
vested prior to or at the onset of the exponential rise in the rate of res-
piration (climacteric). This coincides with a rapid increase in ethylene
production and the transition from fruit development to fruit ripening.
Under the influence of low storage temperatures, restricted oxygen
and/or elevated carbon dioxide concentration, the rate of respiration of
the fruit is reduced and the rate of ripening is retarded (Fidler, 1973).
During storage, apples and many other types of fruit gradually soften,
become more yellow (primarily due to chlorophyll loss) and decrease
in acid content. The extent of development of the aromatic flavor is
highly dependent on cultivar, harvest maturity and duration and regime
of storage.
In addition to changes in fruit chemical composition and structure that
affect quality, physiological disorders may develop in the fruit during
storage. Certain disorders arise through inherent deficiencies in the fruit
at the time of harvest. For example, bitter pit is associated primarily with
deficiency of calcium; this results in dysfunction of cell membranes and
eventual death of groups of cells and the production of characteristic
“corky” lesions in the fruit flesh (Perring, 1986). Other disorders de-
velop progressively as storage is extended, e.g., senescent breakdown
and superficial scald are affected principally by harvest date, storage
conditions and time in store (Wilkinson and Fidler, 1973). Preharvest
conditions during development often have a major influence on suscep-
tibility of fruit to these types of disorders (Sharples, 1973). A further
category of disorders includes those that are induced by the storage con-
ditions themselves (Lidster et al., 1990). These can occur when recom-
mended storage conditions are applied, e.g., low temperature breakdown
(LTB) in Bramley’s Seedling (Bramley) apples and late storage corking
in Cox apples, but result more usually from failure to control carbon
dioxide and oxygen levels.
Figure 4.2 indicates the extent of variability in the quality of Cox ap-
ples harvested from 24 orchards over a six-year period. Within each year
all orchards were harvested on the same date, and in all years fruit was