Agriculture Reference
In-Depth Information
storage conditions. These also have to be addressed as aspects of fruit quality
and its control.
Effects of respiration
Respiration is a key process in ripening. Most, probably all, climacteric ap-
ples would be totally inedible if they retained the high malic acid content
characteristic of the unripe fruit rather than having it used as a substrate for
respiration. The energy released in respiration is essential for the synthesis of
ethylene and aroma volatiles and other physiological changes associated with
ripening. Even after harvest the fruit is alive and its metabolic processes are
maintained by respiration. The duration of its post-harvest life depends on the
rate of this respiration and is primarily extended by slowing down metabolism
and respiration.
Control of respiration
The first of the modern techniques of fruit storage, refrigerated storage in
air, depends for its effectiveness on the fact that the rate of respiration varies
directly with temperature (Table
◦
C
.
). A main-season apple held at
◦
C which, in turn, respires
respires about three times as quickly as one at
◦
C (Hardenburg
et al.
,
about three times as quickly as one at
).
) con-
cluded that the greater the number of cells per unit fruit weight the higher
the respiration rate and, related to this, early maturing cultivars have much
higher respiration rates than later maturing ones. In air at
Different cultivars have very different rates of respiration. Smith (
◦
C the rates
of CO
production, shortly beyond the peak of the climacteric rise in res-
piration, of 'Beauty of Bath' (very early), 'Worcester' (early) and 'Cox' were
times as high, respectively, as those of the very late matur-
ing 'Bramley's Seedling'. These differences also show up even in controlled
atmosphere storage with a number of major international dessert cultivars
having much lower respiration rates than 'Cox's Orange Pippin' (Table
.
,
.
and
.
.
).
Table
.
The effect of temperature on the respiration rates of apples and pears
(mg CO
kg
−
h
−
)
Temperature (
◦
C)
-
-
-
Summer (early) apples
-
-
-
-
-
Autumn apples
-
-
-
-
-
'Bartlett' pear
-
-
-
-
-
From Hardenburg
et al.
(
).
