heart CO
2
-injury as described by Wilkinson and Fidler 1973 increases with CO
2
concentration Argenta et al., 1994; Fan et al., 1997, harvest at
an advanced maturity Volz et al., 1998 and fruit size Park et al., 1997. The risk of CO
2
-injury also increases with fruit nitrogen content Meheriuk et
al., 1994, low storage temperature Smock and Blanpied, 1963 and production under cool tem-
perature growing conditions Lau, 1998. The an- tioxidant diphenylamine DPA prevents the
development of CO
2
-injury in apples Burmeister and Dilley, 1995; Watkins et al., 1997, however,
DPA is not registered for this use. As the use of postharvest chemicals on fresh fruits has received
closer scrutiny in recent years, alternative non- chemical procedures for prevention of physiologi-
cal disorders such as CO
2
-injury would be a useful development in apple storage technology.
Alternative storage protocols may provide a means to reduce the risk of CO
2
-injury. While rapid establishment of CA Sharples and Munoz,
1974; Anderson and Abbott, 1975; Lau et al., 1983 improve post-storage quality of many apple
cultivars, delaying establishment of CA or CO
2
accumulation during storage reduces the inci- dence of CO
2
injury Bramlage et al., 1977; Handwerker, 1979; Elgar et al., 1998. The inci-
dence of
external CO
2
-injury in
‘Bramley Seedling’ apples was also reduced when CA es-
tablished by fruit respiration and by flushing was delayed for 5 and 20 days, respectively Colgan et
al., 1999. Considering these previous reports, the objectives of the present study were to determine
if delayed establishment of CA or CO
2
accumula- tion reduce the incidence of CO
2
injury while maintaining acceptable fruit quality of ‘Fuji’ ap-
ples.
2. Materials and methods
‘Fuji’ apples MalusX domestica Borkh. were harvested 173 and 177 days after full bloom in
1997 and 1998, respectively, from a commercial orchard in Orondo, WA. The fruit were placed
into 0.145 m
3
stainless steel chambers and cooled to 0.5°C within 36 h of harvest. Fruit were stored
at 0.5°C in RA, or in CA at 1.5 kPa O
2
+ 0.05
kPa CO
2
or 1.5 kPa O
2
+ 3 kPa CO
2
under static conditions. Establishment of CA conditions was
initiated 36 h after harvest and atmospheres were established within 72 h of harvest rapid CA.
Chamber O
2
and CO
2
concentrations were moni- tored and corrected automatically Techni-Sys-
tems at 90 min intervals. Atmospheres were established and maintained using compressed air
and CO
2
plus N
2
from a membrane generator system Permea. Hydrated lime [CaOH
2
] 0.1 kg per kg fruit was placed in chambers to help
maintain the CO
2
concentration at 0.05 kPa. For the CA delay treatments, fruit were held in RA at
0.5°C for 2 – 12 weeks after harvest, and then CA 1.5 kPa O
2
+ 3 kPa CO
2
was established and maintained for the remainder of the 8 month
storage period. For the CO
2
delay treatments, fruit were stored in 1.5 kPa O
2
+ 0.05 kPa CO
2
Fig. 1. Internal ethylene concentration IEC and CO
2
produc- tion by ‘Fuji’ apples harvested in 1997 and stored at 0.5°C in
air or controlled atmosphere with 1.5 kPa O
2
+ 3 kPa CO
2
or 1.5 kPa O
2
+ 0.05 kPa CO
2
. Values are means of 18 fruit IEC or three replicate 1 kg samples CO
2
production. Verti- cal bar indicates LSD
0.05
for significant treatment × days inter- action.
Fig. 2. Firmness and titratable acidity of ‘Fuji’ apples harvested in 1997 and 1998 and stored at 0.5°C in air or controlled atmosphere with 1.5 kPa O
2
+ 3 kPa CO
2
or 1.5 kPa O
2
+ 0.05 kPa CO
2
. Values are means of 18 fruit. Vertical bar indicates LSD
0.05
for significant treatment × days interaction.
for 1, 2, 3 or 4 months after harvest, then CO
2
was increased to 3 kPa for the remainder of the 8 month storage period.
Maturity and quality were determined for indi- vidual fruit at harvest and after storage by analy-
ses of fruit respiration rate, internal ethylene concentration IEC, flesh firmness, soluble solids
content SSC and titratable acidity TA. There were three replicate 1 kg samples for respiration
analysis, all other analyses used 18 individual fruit. For respiration analyses, fruit were placed
into 20 l chambers at 20°C supplied with com- pressed, ethylene-free air flowing at 100 ml
min
− 1
. Effluent air was analyzed for CO
2
using a gas
chromatograph Hewlett
Packard 5890
equipped with a methanizer John T. Booker, flame ionization detector and a 0.6 m, 2 mm i.d.
stainless steel column packed with 80 – 100 mesh Poropak Q Supelco. Oven, detector, methanizer
and injection temperatures were 50, 200, 290 and 150°C, respectively. Gas flows for N
2
, H
2
and air were 70, 30 and 300 ml min
− 1
, respectively. Inter- nal ethylene concentrations of individual fruit
were measured on gas samples removed from the fruit core Williams and Patterson, 1962 using a
gas chromatograph Hewlett Packard 5880A equipped with a flame ionization detector and a
0.5 m, 3.2 mm i.d., glass column packed with 80 – 100 mesh Poropak Q. Oven, detector, and
injection temperatures were 90, 200 and 100°C, respectively. N
2
, H
2
, and air flows were 25, 25, and 300 ml min
− 1
, respectively. Flesh firmness was measured on two pared surfaces per fruit
using a penetrometer with an 11 mm tip Lake City Technical. Determination of SSC and TA
used juice freshly prepared with a Champion juicer Plastaket Mfg.. A refractometer Atago
was used to measure SSC and TA was determined by titrating 10 ml of juice with 0.1 M KOH to pH
8.2 using an autotitrator Radiometer.
Severity of watercore, CO
2
-injury wet, well defined, dark brown cortex and pith, flesh
browning light, diffuse, brown in the cortex, and core flush light, diffuse, brown into the core,
pith, were evaluated visually by cutting the fruit in half through the equator. The watercore sever-
ity was scored using a scale from 1, no watercore to 4, very severe watercore. The severity of CO
2
-
Fig. 3. Watercore A and development of CO
2
-injury B in ‘Fuji’ apples. A Apples were stored at 0.5°C in air, 1.5 kPa
O
2
+ 3 kPa CO
2
or 1.5 kPa O
2
+ 0.05 kPa CO
2
. B Apples stored in 1.5 kPa O
2
+ 3 kPa CO
2
. Pooled data from 1997 and 1998 seasons is presented. Both watercore and brown-heart
were scored using a scale from 1 none to 4 severe. Incidence of cavities was rated as 1 none or 2 present. Vertical bar
indicates LSD
0.05
for significant treatment × days interaction.
injury was scored as: 1 none; 2 1 – 30 of flesh cortex and pith dark brown; 3 31 – 60 of flesh
dark brown; and 4 61 – 100 of flesh dark brown. Incidence of cavities was rated as absent
1 or present 2. Flesh browning and core flush were assessed as: absent 1, slight 2 and severe
3.
Data were analyzed using SAS ver 6.12 SAS Institute, 1992. Treatment effects were analyzed
by the ANOVA procedure and treatment mean separation was determined using Fisher’s pro-
tected LSD or Duncan’s multiple range tests P B 0.05.
3. Results and discussion
