Agriculture Reference
In-Depth Information
fruit, is maximized. Removal of within-store ethylene also reduces the extent
to which ripening in the entire population will be synchronized by the ethylene
produced by the earliest ripening fruits.
Several methods of ethylene removal are available. They can involve oxida-
tion with potassium permanganate (Smock,
; Liu,
; Blanpied
et al.
,
), ozone (Fidler and North,
), active oxygen (Scott
et al.
,
), cata-
lysts such as platinum (Dover,
), or adsorption by charcoal or brominated
charcoal (Fidler,
). Some of these methods, e.g. use of potassium perman-
ganate, can be used in small sealed modified atmosphere packs (Smith
et al.
,
). Hypobaric storage has also been used.
The effectiveness of ethylene removal depends on the magnitude of the
problem to be overcome. It is more likely to be effective with early than
with late-picked fruits, with cultivars that are slow to produce much ethy-
lene and with fruits that have been pre-treated either with chemicals that
inhibit ethylene production or with high CO
concentrations with the same
effect.
Under several storage conditions high concentrations of ethylene have less
severe effects than might be anticipated. Oxygen is required in the metabolic
processes underlying some ripening changes including softening (Knee,
).
Ethylene is unable to reverse this low oxygen effect so low oxygen storage
of apples is commercially successful even though concentrations of several
hundred
ll
−
accumulate in the stores (Knee,
). Refrigerated air storage
can also be very effective in prolonging post-harvest life even if the unripe
apples are exposed to ethylene concentrations above
µ
ll
−
.
µ
Calcium and fruit eating-quality
Low calcium concentrations in apple fruits first attracted attention because
they were found to be associated with disorders such bitter pit and York spot.
These may be obvious at harvest but develop in storage, and surface appear-
ance, especially at harvest, may fail to reflect the severity of the disorders after
storage. Low calcium concentration was subsequently found to predispose
apples to other serious physiological disorders such as splitting, lenticel rup-
turing, watercore, breakdown, lenticel blotch pit and confluent pit or crinkle
(Sharples,
). Low
calcium concentrations also increase the susceptibility of apples to storage rots
caused by
Gloeosporium
spp. (Sharples,
; Bramlage
et al.
,
b; Perring,
; Perring
et al.
,
) and to storage scald (Bramlage
et al.
,
). Some of these disorders are discussed in more detail later. Calcium
appears to have fundamental effects not only on these disorders but also on
