Table 1 Effect of pretreatment with hypobaric storage 5 kPa of air
followed by controlled atmosphere CA 1.5 O
2
+ 3 CO
2
or air storage on scald development in ‘Granny Smith’ and ‘Law Rome’ apples at 1°C in 1995
Scald index
a
Storage durations months
Air ‘Granny Smith’
‘Law Rome’ Hypobaric
CA –
2 0c
6 0c
2 6
10 4c
9b 2
– 6
32b 30a
16 85a
– –
2
a
Scald index 0 = none; 1 = slight; 2 = moderate; 3 = severe was normalized to 100 by multiplying the values by 1003.
Means within columns followed by different letters differ at P50.05.
scribed by Wang and Dilley 2000. After a 90- min enclosure, the headspace of a glass jar with
about 1.2 kg of fruit was sampled by solid phase microextraction SPME equilibrating the fibre
for 4 min to absorb volatiles. The volatiles were measured by gas chromatographymass spec-
trometry GCMS as described by Song et al. 1997 to determine volatile productionevolution.
At the same time intervals, 14 mg of epicuticular wax sample was removed from five fruit in each
treatment and placed in a 2-ml glass vial for 3 h at 20°C to determine the amount of a-farnesene and
MHO partitioned in the epicuticular wax by SPMEGCMS as described above. Fruit in paral-
lel samples were used for fruit firmness and ripen- ing changes immediately upon removal from
storage and again after 7 days at 20°C data not presented.
3. Results
3
.
1
. Hypobaric studies in
1995
–
97
‘Granny Smith’ and ‘Law Rome’ apples stored hypobarically for 2 months then under CA at
1.5 O
2
plus 3 CO
2
for 6 months did not develop scald during storage Table 1. A slight
amount of scald developed on the fruit when stored in air for a further 10 months. Fruit stored
hypobarically and then in air for 6 or 16 months developed low scald indices Table 1. Fruit stored
2
.
4
. Hypobaric studies
1997 98
‘Law Rome’ and ‘Granny Smith’ fruit were stored hypobarically or in air at 1°C. Fruit were
placed under hypobaric storage immediately after harvest or after 0.5, 1, 2, 3, 4, 5 or 6 months
storage in air at 1°C to determine the effects of delaying imposition of hypobaric storage on
ripening and scald development, and production of a-farnesene and MHO. After total 6 months of
storage, fruit were removed from hypobaric or air storage and transferred to 20°C in air in 4-l glass
jars. a-Farnesene and MHO production rates at daily or bi-daily intervals were measured as de-
Table 2 Effect of hypobaric 5 kPa of air or controlled atmosphere CA andor air storage on scald development of ‘Granny Smith’ and
‘Law Rome’ apples at 1°C in 1996 Scald index
a
Storage durations months Hypobaric
‘Law Rome’ ‘Granny Smith’
Air CA 3O
2
0 CO
2
CA 1.5O
2
3CO
2
– –
0e 8
– 0f
– 4
8 0e
– 0f
– –
8 10
38d 32d
– 8
– –
8e 10e
8 –
77b 88b
– –
– –
2 6
62c 50c
– –
– 8
100a 100a
a
Scald index 0 = none; 1 = slight; 2 = moderate; 3 = severe was normalized to 100 by multiplying the values by 1003. Means within columns followed by different letters differ at P50.05.
Fig. 1. Effect of delaying hypobaric storage on control of scald of ‘Granny Smith’ and ‘Law Rome’ apples. Fruit was stored in
air at 1°C prior to storing them hypobarically at 5 kPa in air. After 6 months of storage, fruit were removed from hypobaric
storage and scald index 0 = none; 1 = slight; 2 = moderate; 3 = severe was measured after 7 days poststorage at 20°C.
The Scald index was normalized to 100 by multiplying the values by 1003.
Progressively longer periods of storage in air at 1°C before ‘Granny Smith’ apples were placed in
hypobaric storage resulted in a greater burst of a
-farnesene production Fig. 2A, but in contrast, for ‘Law Rome’ fruit a nearly opposite trend was
found Fig. 2B. a-Farnesene production rates were highest for ‘Law Rome’ apples stored hypo-
barically within 1 month after harvest but lowest in ‘Granny Smith’ apples treated similarly. The
a -farnesene production of ‘Granny Smith’ fruit
placed in hypobaric storage within 1 month of harvest steadily increased after transferring the
fruit to air at 20°C, eventually matching or ex- ceeding that of fruit stored after 2 months delay
Fig. 2A. The amount of a-farnesene partitioned in the cuticle largely followed the pattern of its
volatilization into the headspace from whole fruit Fig. 2C. Upon transfer to 20°C, the a-farnesene
evolution rate from cuticle of ‘Law Rome’ apples
Fig. 2. Change in a-farnesene levels in headspace A, B and in the epicuticular wax C, D of ‘Granny Smith’ A, C and
‘Law Rome’ B, D apples stored in air for 0 – 6 months before hypobaric storage at 5 kPa in air.
hypobarically for 8 months plus 4 months in air did not develop scald Table 2, whereas scald did
develop after an additional 6 months of storage in air. ‘Granny Smith’ and ‘Law Rome’ fruit stored
under CA with 1.5 O
2
for 8 months developed slight scald with indices of 8.3 and 10.3, respec-
tively; those stored for 2 months in CA then moved to air or those under CA at 3 or more O
2
scalded severely Table 2. Collectively, the data indicate that apples stored hypobarically do not
scald during storage but may do so after subse- quent extended periods of time in a static air
atmosphere Table 2. Moreover, CA storage con- trols scald less effectively than hypobaric storage.
3
.
2
. Hypobaric studies
1997 98:
Hypobaric storage at 5 kPa prevented scald of ‘Granny Smith’ and ‘Law Rome’ apples only if
they were placed under hypobaric conditions within 1 month after harvest following interim
storage in air at 1°C Fig. 1. After 3 months delay, scald index 80 for ‘Granny Smith’ and 65
for ‘Law Rome’ was similar to that for fruit stored continuously in air 82 for ‘Granny Smith’
and 78 for ‘Law Rome’.
Fig. 3. Change in 6-methyl-5-hepten-2-one MHO levels in headspace A, B and in the epicuticular wax C, D of
‘Granny Smith’ A, C and ‘Law Rome’ B, D apples stored in air for 0 – 6 months before hypobaric storage at 5 kPa in air.
storage Fig. 3C,D. Based on the measurements taken for five dif-
ferent cvs. including scald susceptible and resis- tant cvs., the production rates of a-farnesene and
MHO were low during 7 months of hypobaric storage but quickly increased upon removal from
storage and transfer to air at 20°C. The rates then, decreased sharply after about a week Fig.
4. The ‘Granny Smith’ cv. had the lowest rates among the five cvs. examined. None of the cvs.
stored hypobarically scalded, whereas all scalded except ‘Golden Delicious’ when stored in air. In
comparison, MHO evolution from air-stored ‘Granny Smith’ fruit after 5.5-months storage and
transfer to 20°C, was 5-fold higher than that hypobarically stored fruit data not shown.
Fig. 4. Change in headspace levels of a-farnesene A and its oxidation product 6-methyl-5-hepten-2-one B for different
cultivars of apples after 7 months of hypobaric storage at 1°C and transfer to 20°C in air in 1997. Scald did not develop on
any fruits stored hypobarically but developed on all others except ‘Golden Delicious’ stored in air at atmospheric pres-
sure.
was higher for apples which were placed under hypobaric condition within 2 months than for
those hypobarically stored after more than 2 months in air Fig. 2D. This again mimicked the
pattern of the rate of a-farnesene evolution into the headspace by whole apples.
MHO evolution rates were progressively greater as the delay to hypobaric storage increased in
both cvs. Fig. 3A,B. Following a burst observed 1 day after transfer to 20°C, the rate of MHO
evolution gradually diminished. Fruit which were under hypobaric storage within 1 month produced
a nearly constant, low level of MHO. MHO which accumulated in the cuticle of fruit delayed
to hypobaric storage gradually dissipated upon transfer of fruit to 20°C, however, if the fruit were
under hypobaric condition within 1 month, these fruit had lower levels of MHO evolution during
the first 3 days after removal from hypobaric
4. Discussion
