constant k
2
= − P
j
· A
ch
· R · T + 273.15V
ch
, s
− 1
in the function used to derive fitted curves to plots of chamber atmosphere composition with
respect to gas j p
j ch,t
versus time after flushing with nitrogen.
p
j ch,t
= p
j i
· 1 − e
k
2
− t
6 t
0.99
= −
ln100 k
2
7 Permeance to gas j can be estimated from k
2
for the same gas as follows:
p
j
= k
2, j
· V
ch
A
ch
· R · T + 273,15 8
which, given the values of V
ch
, A
ch
and T used in this study for chambers over intact and wounded
cuticle equated
to −
5.44 × 10
− 6
· k
2,j
and −
2.27 × 10
− 5
· k
2,j
, respectively.
2. Materials and methods
Two experiments were conducted at 20.4 9 0.32°C, 96 9 1.7 relative humidity on freshly
harvested, greenhouse-grown sweet peppers Cap- sicum annuum, cv. Reflex obtained directly from
a local grower.
2
.
1
. Experiment
1
. Physical and physiological equilibration time for O
2
and CO
2
in chambers adhered o6er wounded fruit surface
Sixty-four fruit were assigned at random to two treatments: ‘control’ no treatment; 28 fruit and
‘wounded’ 36 fruit. In the case of wounded fruit, a disc of outer tissues including cuticle and epider-
mis 5.8 mm diameter; 0.5 mm average thickness was removed aseptically from the surface of each
fruit time after wounding, t
aw
= 0 h. A glass
chamber 9.65 mm internal diameter, 0.996 – 1.080 ml was adhered over the wound with Araldite 24
h curing and the fruit left overnight for the glue to cure. Chambers on eight of the 36 fruit were
supported in frames to prevent dislodging the chamber from the waxy fruit surface during re-
peated sampling. Septa and water seals were then added to all chambers see Fig. 1 in Rajapakse et
al., 1990 and silicone grease used to cover the glue seal t
aw
= 16 h.
Samples of flesh atmosphere were taken de- structively by direct removal Banks, 1983 from
the flesh of the pericarp wall on four fruit from each treatment at t
aw
= 16, 28, 40, 52, 64, 76, 88
and 112 h. Special care was taken to avoid con- tamination of flesh atmosphere samples with ex-
ternal or fruit cavity atmospheres by filling the fruit cavity with water immediately before sam-
pling and withdrawing samples of flesh atmo- sphere whilst fruit were immersed in water.
Repeated samples were taken from chambers on the eight fruit in frames at t
aw
= 16, 40, 52, 64, 76,
88 and 112 h to estimate long term trends with time. In addition, vials on these fruit were flushed
with nitrogen after sampling at t
aw
= 16 and 64 h
and resampled after an additional 0, 0.5, 1, 4 and 12 h after flushing. Samples of flesh and cavity
atmospheres of these fruit were taken by direct removal at t
aw
= 112 h.
2
.
2
. Experiment
2
. Physical equilibration time for O
2
and CO
2
le6els in chambers adhered o6er non-wounded fruit surface
Two chambers, mounted in supporting frames to facilitate repeated sampling, were adhered adja-
cent to each other on the surface of each of eight peppers, one over a surface wound as described in
Experiment 1 and the other over intact, non-dam- aged surface. After sealing the chambers, fruit
were left for a further 48 h before sampling the contents of chambers over wounds t
aw
= 48 h.
Chambers over intact surface were then flushed with nitrogen and their contents were sampled at
t
aw
= 52 h. All chambers were sampled at t
aw
= 60
and 72 h. Direct removal was used to take sam- ples of cavity atmosphere from each fruit t
aw
= 96 h, and subsequently from the flesh of the fruit
following replacement of the cavity atmosphere with water to prevent accidental contamination
with contents of the cavity.
2
.
3
. Gas analysis Aliquot gas samples of atmospheres were taken
with gas-tight glass syringes Hamilton, 100 mm
3
.
Oxygen and CO
2
contents were determined using an O
2
electrode Citicell CS type, City Technol- ogy Ltd., London, UK in series with a miniature
infra-red CO
2
transducer Analytical Develop- ment Company, Hoddesdon, UK with O
2
-free N
2
as carrier gas flow rate 580 mm
3
s
− 1
. Output signals were analysed using integrators Hewlett
Packard, model 3394A. Commercially prepared standards, BOC Special Gases, Wellington, NZ
were used for calibration of the gas analysers 2.05 kPa CO
2
, 5.1 kPa O
2
or 10.01 kPa CO
2
, 20.1 kPa O
2
, when held at one standard atmosphere total pressure.
2
.
4
. Data analysis For experiment 1, differences between samples
taken from flesh or cavity by direct removal and those from chambers held on to the fruit surface
with frames were analysed separately by time GLM procedure; SAS Institute, 1988. Values for
k
2
for the equilibration of both O
2
and CO
2
in chambers over wounded surface experiment 1
and intact cuticle experiment 2 were obtained by non-linear regression SAS Institute, 1988 of p
O
2
ch,t
and p
CO
2
ch,t
against time using Eq. 6. Before analy- sis, data at any given time were standardised by
dividing by the final values when equilibration was complete for these variables in chambers
over wounded surface, which were taken to repre- sent internal atmosphere composition. The same
general form of function as that in Eq. 6 was fitted to longer term data from experiment 2 to
characterise physiological drift in internal atmo- sphere estimates with time.
3. Results
