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Effect of Storage Temperature on Fruit Ripening in Three Kiwifruit Cultivars

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The responses of three kiwifruit cultivars, Actinidia chinensis ‘Sanuki Gold’, A. chinensis ‘Rainbow Red’, and A. deliciosa ‘Hayward’ to various storage temperatures (0, 5, 10, 15 and 20°C) for 8 weeks were investigated. The rate of fruit which initiated ethylene production due to rot development increased with increases in storage temperature. Early-maturing cultivars, ‘Rainbow Red’ and ‘Sanuki Gold’ fruit stored at 5, 10, and 15°C showed drastic softening and a decrease in titratable acidity (TA) to an edible level within 4 weeks without detectable ethylene production, whereas fruit stored at 0 and 20°C maintained high firmness and TA even after 8 weeks unless they were infected with rot. A late-maturing cultivar, ‘Hayward’ fruit stored at 5 and 10°C softened more rapidly than when stored at 0, 15, or 20°C. Treatment with 1-Methylcyclopropene (1-MCP) did not suppress the low temperature modulated fruit ripening in any cultivars, indicating its independence from ethylene. These results suggest that ‘Sanuki Gold’ and ‘Rainbow Red’ are more sensitive to low temperatures compared to ‘Hayward’ and the sensitivity is involved in the determination of storage life and how early the fruit matures on the vine.
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Effect of Storage Temperature on Fruit Ripening in Three Kiwifruit Cultivars
William Olubero Asiche1**, Oscar Witere Mitalo1**, Yuka Kasahara1, Yasuaki Tosa1,
Eric Gituma Mworia2, Koichiro Ushijima1, Ryohei Nakano1 and Yasutaka Kubo1*
1Graduate School of Environmental and Life Science, Okayama University, 700-8530 Okayama, Japan
2Meru University of Science and Technology, 972-60200 Meru, Kenya
The responses of three kiwifruit cultivars, Actinidia chinensis ‘Sanuki Gold’, A. chinensis ‘Rainbow Red’, and
A. deliciosa ‘Hayward’ to various storage temperatures (0, 5, 10, 15 and 20°C) for 8 weeks were investigated.
The rate of fruit which initiated ethylene production due to rot development increased with increases in
storage temperature. Early-maturing cultivars, ‘Rainbow Red’ and ‘Sanuki Gold’ fruit stored at 5, 10, and
15°C showed drastic softening and a decrease in titratable acidity (TA) to an edible level within 4 weeks
without detectable ethylene production, whereas fruit stored at 0 and 20°C maintained high firmness and TA
even after 8 weeks unless they were infected with rot. A late-maturing cultivar, ‘Hayward’ fruit stored at 5 and
10°C softened more rapidly than when stored at 0, 15, or 20°C. Treatment with 1-Methylcyclopropene (1-
MCP) did not suppress the low temperature modulated fruit ripening in any cultivars, indicating its
independence from ethylene. These results suggest that ‘Sanuki Gold’ and ‘Rainbow Red’ are more sensitive
to low temperatures compared to ‘Hayward’ and the sensitivity is involved in the determination of storage life
and how early the fruit matures on the vine.
Key Words: early-maturing cultivar, late-maturing cultivar, low-temperature storage, rot incidence.
Introduction
The plant hormone ethylene initiates ripening-
associated events in kiwifruit, such as increased respira-
tion, softening, reduction in acidity, conversion of
starch to sugar, and aroma development as it is a cli-
macteric fruit (Antunes et al., 2000; Mworia et al.,
2010). Kiwifruit has been believed to be extremely sen-
sitive to ethylene, which accelerates ripening (Ritenour
et al., 1999; Yin et al., 2010). The presence of ethylene
in the storage room shortens kiwifruit storage life and
hence, it is a major challenge during long-term storage
(Pranamornkith et al., 2012). Thus, the main areas of
investigation into how to extend kiwifruit storage life
are ethylene elimination and low temperature control
(Koukounaras and Sfakiotakis, 2007).
In kiwifruit, major postharvest diseases are soft rot
caused by Botryoshaeria spp. and Phomopsis spp. and
stem-end rot by Diaporthe actinidia, which are epiphyt-
Received; June 16, 2016. Accepted; September 13, 2016.
First Published Online in J-STAGE on January 14, 2017.
This work was supported in part by a Grant-in-Aid for Scientific
Research (grant no. 24380023, no. 16H04873) from the Japan Society
for the Promotion of Science, Japan. 
* Corresponding author (E-mail: ykubo@okayama-u.ac.jp).
** These authors contributed equally to this work
ic at harvest, and penetrate inside the fruit during stor-
age (Kinugawa, 2000). Once the pathogenic fungus
invades a single fruit, it induces ethylene biosynthesis
that affects other surrounding fruit (Yano and
Hasegawa, 1993). Therefore, in order to understand the
ripening physiology and evaluate the storage potential
of kiwifruit, especially at room temperature, we have to
eliminate the effects of disease-induced ethylene.
1-Methylcyclopropene (1-MCP), a synthetic cyclic
olefin that is used to extend storage life in many climac-
teric fruit, inhibits ethylene action through interaction
with ethylene receptors (Sisler and Serek, 1997). Pre-
storage treatment with 1-MCP significantly delays the
increase in ethylene production and softening of
‘Hayward’ fruit during their shelf life at room tempera-
ture, after short- and medium-term cold storage
(Koukounaras and Sfakiotakis, 2007). In kiwifruit,
‘Bartlett’ pears and ‘Charantais’ melons, fruit treated
with 1-MCP exhibited significant extension of storage
and shelf life (Asiche et al., 2016; Nishiyama et al.,
2007; Villalobos-acuña et al., 2011). In this study, we
used 1-MCP treatment and spatial isolation to eliminate
the effects of ethylene produced by adjoining diseased
fruit.
Storage temperature plays a pivotal role in fruit me-
tabolism during long-term storage, causing changes in
This article is an Advance Online Publication of the authors’ corrected proof. Note that minor changes may be made before final version publication.
The Horticulture Journal Preview
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physical and chemical attributes and in the aroma com-
position of various fruits (Antunes and Sfakiotakis,
2002; Antunes et al., 2000; Ritenour et al., 1999). The
kiwifruit industry utilizes a cold storage temperature of
0–4°C to slow down the ripening process and extend
fruit life (Arpaia et al., 1987; Pranamornkith et al.,
2012). Low temperatures generally inhibit microbial
growth and suppress metabolic changes, thus maintain-
ing fruit quality during storage (Wang and Wang,
2009).
The genus Actinidia consists of 55 species and 76
taxa native to Asia, including a wide array of cultivars
(Kim et al., 2009; Thompson et al., 2000; Wang and
Gleave, 2012). Actinidia deliciosa ‘Hayward’ and
A. chinensis ‘Hort16A’ are widely commercialized
kiwifruit cultivars, and many other novel cultivars have
been introduced and grown commercially worldwide
(Kim et al., 2009). In Japan, A. chinensis ‘Sanuki Gold’
and A. chinensis ‘Rainbow Red’ are new cultivars gain-
ing commercial prominence with the most notable fruit
attributes being smooth skin and a high soluble solids
content (SSC). However, these cultivars have a relative-
ly short storage life compared to A. deliciosa
‘Hayward’. ‘Sanuki Gold’, bred in Kagawa, Japan, is a
tetraploid (4n) with large fruit size (200 g), brown skin,
golden yellow flesh, and high SSC (16%), whereas
‘Rainbow Red’ (2n) has green, smooth skin with red
concentric rings, weighs 100 g, and has an extremely
high SSC (18%) (Mworia et al., 2010; Nishiyama et al.,
2008). ‘Hayward’ is medium-sized (120 g) and has
hairy skin and a lower SSC (14%) than the other two
cultivars. ‘Sanuki Gold’ and ‘Rainbow Red’ are early-
maturing types harvested in early October and late
September, respectively, in contrast to ‘Hayward’,
which is a late-maturing type harvested in early
November. The most important postharvest disparity
between the cultivars is storage life; ‘Hayward’ can be
stored for up to 6 months (Arpaia et al., 1987), whereas
‘Sanuki Gold’ and ‘Rainbow Red’ can be stored for
only 1 or 2 months even at low temperature. Thus, it
will be useful to study ‘Sanuki Gold’ and ‘Rainbow
Red’ in order to determine the physiological differences
among cultivars and to develop appropriate methods for
long-term storage.
Our previous research on the kiwifruit A. chinensis
‘Sanuki Gold’ showed that fruit stored at 5°C ripened
faster than fruit stored at room temperature, accompa-
nied by elevated expression of specific ripening-
associated genes, encoding cell wall-modifying
enzymes, carbohydrate metabolism, and transcription
factors in an ethylene-independent manner when effects
of disease-induced ethylene was eliminated (Mworia
et al., 2012). Furthermore, during low-temperature stor-
age, repeated application of 1-MCP failed to suppress
changes in firmness and titratable acidity. It was con-
cluded that exposure to low temperature accelerated
ripening of ‘Sanuki Gold’ kiwifruit. There is little infor-
mation on the impact of prolonged storage under vari-
ous storage temperature regimes in different kiwifruit
cultivars. The objectives of our study were to assess the
effect of different storage temperatures (0, 5, 10, 15,
and 20°C) on development of ripening rot and ripening
characteristics in ethylene-free conditions using three
kiwifruit cultivars ‘Sanuki Gold’, ‘Rainbow Red’, and
‘Hayward’.
Materials and Methods
Plant materials
A. chinensis ‘Sanuki Gold’ and A. chinensis
‘Rainbow Red’ fruit were obtained from a commercial
orchard in Kagawa, Japan. ‘Sanuki Gold’ fruit were
harvested on October 5, 2011 while ‘Rainbow Red’
fruit were harvested on September 27, 2011.
A. deliciosa ‘Hayward’ fruit were harvested from the
experimental orchard at Okayama University, Japan on
November 7, 2011. Kiwifruit were immediately trans-
ported to a postharvest laboratory at Okayama Univer-
sity, Japan where they were sorted to obtain fruit of
uniform size and without defects or blemishes.
Ethylene and fruit rot screening
To monitor for disease infections, ethylene produc-
tion of all fruit was measured individually at harvest
and a few fruit were found to be producing ethylene.
These fruit were set aside and monitored at room tem-
perature for a few days. Shortly thereafter, rot symp-
toms developed, indicating that the initiation of
ethylene production was due to fruit rot. Therefore, we
decided to conduct strict ethylene and fruit rot screen-
ing (twice a week) to remove the effects of disease-
induced ethylene during the entire experimental period.
Once ethylene production >0.02 nL·g−1·h−1 was de-
tected, the fruit were transferred to a separate room and
monitored at room temperature. Ethylene measurements
were conducted by incubating individual fruit in a 0.4 L
container. After 1 h, 1 mL of headspace gas was with-
drawn and injected into a gas chromatograph (Model-
GC8 CMPF; Shimadzu, Kyoto, Japan) equipped with a
flame ionization detector (set at 200°C) and an acti-
vated alumina column 4 mm × 1 m) set at 80°C
(Mworia et al., 2010).
Treatments and storage conditions
Fruit at the commercial harvesting stage were stored
spatially separated (5 cm apart) in order to avoid effects
of disease-induced ethylene. The experimental design
consisted of control fruit (CON), 1-MCP, and five tem-
perature regimes (0, 5, 10, 15, and 20°C). Treatment
with 1-MCP was conducted twice a week throughout
the duration of storage by exposing fruit to 5 μL·L−1 of
1-MCP (SmartFreshTM, Rohm and Hass, Philadelphia,
PA, USA) for 12 h, according to Mworia et al. (2010,
2012).
2W. O. Asiche, O. W. Mitalo, Y. Kasahara, Y. Tosa, E. G. Mworia, K. Ushijima, R. Nakano and Y. Kubo
Evaluation of fruit quality indices
Fruit firmness (outer pericarp and core), SSC, and
TA were determined at week 0, 2, 4, 6, and 8 using 5
biological replications. Fruit were exposed to room
temperature for 2 h before assessment. Fruit skin was
sliced off from two opposite cheeks along the equatorial
region and outer pericarp firmness was subsequently
measured using a penetrometer (model SMT-T-50;
Toyo Baldwin, Tokyo, Japan) fitted with a 5-mm
plunger (Asiche et al., 2016). The SSC of the fruit juice
was determined using a digital Atago PR-1 refrac-
tometer (Atago Co. Ltd, Tokyo, Japan) and expressed
as Brix (%). TA was determined by titrating the extract
against 0.1N NaOH and then expressed as percentage
citric acid equivalents.
Results
Fruit rot incidence at different storage temperatures
For all three cultivars and storage temperatures, fruit
that initiated ethylene production were isolated and
monitored in a separate room as described in the previ-
ous section. These fruit increased ethylene production
and developed visible rot symptoms within a few days.
As shown in Figure 1, the highest percentage of
ethylene-producing fruit was observed during storage at
20°C. In fact, ‘Rainbow Red’ CON fruit and ‘Sanuki
Gold’ 1-MCP fruit at 20°C could only be stored for 4
and 6 weeks respectively since most of the fruit pro-
duced ethylene (Fig. 1A, B). Notably, storage of fruit at
lower temperatures (0 and 5°C) significantly reduced
fruit rot incidence in all the three cultivars with rot inci-
dence being virtually absent at 0 and 5°C. Nevertheless,
fruit without ethylene production did not develop rot
symptoms throughout the experimental period and were
considered healthy fruit. These fruit were used for fur-
ther analysis of ripening characteristics.
Changes in fruit firmness
Figure 2 shows the outer pericarp firmness of the
three kiwifruit cultivars for the CON and 1-MCP fruit.
The outer pericarp firmness of ‘Rainbow Red’ CON
and 1-MCP fruit stored at 5, 10, and 15°C drastically
decreased from 37 N at harvest to 2–6 N at 4 weeks
(Fig. 2A, B). However, fruit stored at 0 and 20°C main-
tained high firmness of approximately 35 N and 20 N,
respectively for both the CON and 1-MCP groups after
4 weeks. ‘Sanuki Gold’ CON and 1-MCP fruit at 5, 10,
and 15°C also showed a sharp decrease in outer peri-
carp firmness from ~30 N at harvest to ~4 N at 4 weeks
(Fig. 2C, D). At this time point, however, both ‘Sanuki
Gold’ CON and 1-MCP fruit at 0 and 20°C still had a
higher firmness of approximately 25 N. Conversely,
‘Hayward’ fruit exhibited slower softening of the outer
pericarp compared to the other cultivars. As shown in
Figure 2E and F, both ‘Hayward’ CON and 1-MCP
fruit at 5 and 10°C decreased in terms of outer pericarp
firmness at a faster rate (after 4 weeks) than fruit at 0,
15, and 20°C. However, the firmness of ‘Hayward’ fruit
at 5 and 10°C even after 8 weeks was higher than that
of ‘Rainbow Red’ and ‘Sanuki Gold’ at 4 weeks.
Changes in SSC and TA
Figure 3 shows the changes in SSC in the three kiwi-
fruit cultivars during storage. ‘Rainbow Red’ fruit stor-
ed at 5, 10, 15, and 20°C in both the CON and 1-MCP
groups showed a more rapid increase in SSC, achieving
>15% by 4 weeks (Fig. 3A, B). However, the SSC of
both CON and 1-MCP fruit at 0°C showed a slower in-
crease in SSC, achieving <15% by 8 weeks. Converse-
ly, ‘Sanuki Gold’ CON and 1-MCP fruit at 0 and 20°C
showed the least increase in SSC, to 13% after 4 weeks,
whereas fruit at 5, 10, and 15°C showed a consistent in-
crease in SSC reaching a maximum of approximately
0
20
40
60
80
100
02468
Fruit producing ethylene (%)
‘Rainbow Red’
0
20
40
60
80
100
0 2 4 6 8
Fruit producing ethylene (%)
‘Sanuki Gold’
0
20
40
60
80
100
02468
Fruit producing ethylene (%)
‘Hayward
0CON
01–MCP
5CON
51–MCP
10CON
101–MCP
15CON
×151–MCP
20CON
201– MCP
Storage duraon (Weeks)
A B C
×
Fig. 1. Effect of storage temperature and 1-MCP treatment on percentage of ethylene-producing fruit (rot incidence) in ‘Rainbow Red’, ‘Sanuki
Gold’, and ‘Hayward’. All fruit that initiated ethylene production developed rot symptoms within a few days after transfer to a separate
room. Therefore, the percentage of ethylene-producing fruit is identical to fruit rot incidence. Treatment with 1-MCP was performed twice a
week during the experimental period.
Hort. J. Preview 3
0
10
20
30
40
02468
‘Sanuki Gold’ (CON)
Firmness (N)
Storage duraon (Weeks)
Firmness (N)
0
10
20
30
40
50
02468
‘Rainbow Red’ (CON)
0
10
20
30
40
02468
‘Rainbow Red’ (1-MCP)
0
10
20
30
40
02468
‘Sanuki Gold’ (1-MCP)
0
10
20
30
40
02468
‘Hayward’ (CON)
0
10
20
30
40
02 4 6 8
‘Hayward’ (1-MCP)
10CON
0CON
5CON
15CON
20CON
01–MCP
51–MCP
101–MCP
×151–MCP
201–MCP
A
B
C
D
E
F
×
Fig. 2. Effect of storage temperature and 1-MCP treatment on outer pericarp firmness of ‘Rainbow Red’, ‘Sanuki Gold’, and ‘Hayward’ fruit.
Treatment with 1-MCP was performed twice a week during the experimental period. Each data point is composed of 5 fruit with SE bars.
Brix (%) Brix (%)
Storage duraon (Weeks)
0
5
10
15
20
25
02468
‘Rainbow Red’ (CON)
0
5
10
15
20
25
0 2 4 6 8
‘Rainbow Red’ (1-MCP)
0
5
10
15
20
02468
‘Sanuki Gold’ (CON)
0
5
10
15
20
02468
‘Sanuki Gold’ (1-MCP)
0
4
8
12
16
02468
‘Hayward’ (CON)
0
4
8
12
16
0 2 4 6 8
‘Hayward’ (1-MCP)
10CON
0CON
5CON
15CON
20CON
01–MCP
51–MCP
101–MCP
×151–MCP
201–MCP
A C E
B D E
×
Fig. 3. Effect of storage temperature and 1-MCP on SSC of ‘Rainbow Red’, ‘Sanuki Gold’, and ‘Hayward’ fruit. Treatment with 1-MCP was
performed twice a week during the entire experimental period. Each data point is composed of 5 fruit with SE bars.
4W. O. Asiche, O. W. Mitalo, Y. Kasahara, Y. Tosa, E. G. Mworia, K. Ushijima, R. Nakano and Y. Kubo
15% after 6 weeks (Fig. 3C, D). For ‘Hayward’ CON
and 1-MCP fruit, the SSC increased gradually in all
temperature regimes, attaining a maximum of approxi-
mately 14% within 8 weeks, although the rate was
slower in fruit at 0°C (Fig. 3E, F).
The TA of ‘Rainbow Red’ CON and 1-MCP fruit at
5, 10, and 15°C decreased more rapidly than that of
fruit at 0 and 20°C to below 1% within 4 weeks
(Fig. 4A, B). A similar trend was observed in the TA of
both ‘Sanuki Gold’ CON and 1-MCP fruit, with TA
rates decreasing more rapidly in fruit at 5 and 10°C
than in fruit at 0 and 20°C (Fig. 4C, D). ‘Hayward’ fruit
showed a higher TA level than the other two cultivars
both at harvest and after 8 weeks, as well as a slower
rate of decrease in TA during storage (Fig. 4E, F). After
8 weeks of storage, the TA level of ‘Hayward’ 1-MCP
fruit was lower at 5 and 10°C than at 15 and 20°C.
Discussion
Ethylene-dependent and -independent fruit ripening in
kiwifruit
The plant hormone ethylene is responsible for ripen-
ing in climacteric fruit, causing changes in fruit attri-
butes such as softening, increases in SSC, and reduction
in TA (Mworia et al., 2010; Tacken et al., 2010). Exog-
enous application of ethylene or propylene, an ethylene
analogue, accelerated kiwifruit ripening to within 5
days at room temperature, accompanied by endogenous
ethylene production (Antunes et al., 2000; Mworia
et al., 2010). Conversely, application of 1-MCP, an
ethylene perception inhibitor, suppressed ethylene-
controlled ripening in kiwifruit even after initiation of
ripening, as also observed in melons, pears, apples, and
tomatoes (Boquete et al., 2004; Ergun et al., 2005;
Nakatsuka et al., 1997; Nishiyama et al., 2007; Pre-
Aymard et al., 2003). It is believed that kiwifruit are
highly sensitive to exogenous ethylene (Arpaia et al.,
1987; Michell, 1990). Thus, in the present study, we
conducted frequent screening to remove ethylene-
producing fruit. These fruit developed rot symptoms
within a few days, so ethylene was attributed to disease
stress (Fig. 1). Fruit rot in kiwifruit is mainly caused by
Botryoshaeria sp. and Phomopsis sp. (Kinugawa,
2000), which infect fruit on the vine and are manifested
during storage especially at high temperatures and
under moist conditions. According to Sfakiotakis et al.
(1997), kiwifruit do not start autocatalytic ethylene pro-
duction at harvest unless the fruit sustain mechanical
damage or pathogen attack. The present results agree
with this finding since healthy ‘Rainbow Red’, ‘Sanuki
Gold’, and ‘Hayward’ kiwifruit did not produce ethyl-
ene throughout the storage period at the various temper-
atures. As previously reported by Yano and Hasegawa
(1993), ethylene evolution in healthy kiwifruit is stimu-
lated by ethylene stemming from diseased fruit packed
in the same container or by exogenous ethylene gas.
Storage duraon (Weeks)
Titratable acids (%) Titratable acids (%)
0
0.5
1
1.5
2
02468
‘Rainbow Red’ (CON)
0
0.5
1
1.5
2
2.5
3
02468
Sanuki Gold’ (CON)
0
0.5
1
1.5
2
2.5
3
02468
‘Hayward’ (CON)
0
0.5
1
1.5
2
02468
‘Rainbow Red’ (1-MCP)
0
0.5
1
1.5
2
2.5
3
02468
‘Sanuki Gold’ (1-MCP)
0
0.5
1
1.5
2
2.5
3
02468
‘Hayward’ (1-MCP)
10CON
0CON
5CON
15CON
20CON
01–MCP
51–MCP
101–MCP
×151–MCP
201–MCP
A
B
C
D
E
F
×
Fig. 4. Effect of storage temperature and 1-MCP on TA of ‘Rainbow Red’, ‘Sanuki Gold’, and ‘Hayward’ fruit. Treatment with 1-MCP was
performed twice a week during the experimental period. Each data point is composed of 5 fruit with SE bars.
Hort. J. Preview 5
Based on this, fruit producing ethylene as a result of
disease infection were isolated through strict and fre-
quent screening to avoid contamination and ensure that
fruit sampled at various temperatures were completely
ethylene-free. This procedure resulted in a storage life
of more than 4 weeks for fruit stored at 20°C, which is
much longer than that previously observed in other
studies (Kim et al., 1999; Schotsmans et al., 2008;
Taglienti et al., 2009).
According to our previous study, ‘Sanuki Gold’ kiwi-
fruit with undetectable ethylene production exhibited
low temperature-modulated ripening whereby fruit stor-
ed at 5°C ripened faster than fruit at 25°C (Mworia
et al., 2012). Treatment of fruit stored at 5°C with 1-
MCP did not inhibit the ripening process indicating that
‘Sanuki Gold’ fruit ripened in response to low tempera-
ture independent of ethylene. In the present study,
healthy ‘Rainbow Red’ and ‘Sanuki Gold’ fruit with
undetectable ethylene production ripened faster during
storage at 5, 10, and 15°C compared to fruit at 0 and
20°C (Figs. 2 and 4). Similarly, ‘Hayward’ fruit with
undetectable ethylene production ripened faster at 5 and
10°C than fruit at 0, 15, and 20°C. Repeated 1-MCP
treatment did not suppress ripening since both CON and
1-MCP groups depicted a similar ripening pattern at the
respective storage temperatures. Therefore, the present
results suggest that kiwifruit ripening is modulated by
temperature independent of ethylene and the effect of
temperature on kiwifruit ripening is manifested in all
cultivars. In the absence of ethylene, the rate of ripen-
ing in healthy kiwifruit is mainly dependent on the stor-
age temperature. Low-temperature-induced ripening
has also been reported in other fruit species such as
pears, apples, and plums, but this is assumed to be fa-
cilitated by ethylene biosynthesis due to cold stress,
contrary to what we observed in kiwifruit (Candan
et al., 2008; El-Sharkawy et al., 2003; Kim et al., 1999;
Tacken et al., 2010). Furthermore, some fruit attributes
are still manifested even when ethylene biosynthesis is
suppressed. Experiments on transgenic apple fruit with
suppressed 1-aminocyclopropane-1-carboxylic acid
synthase (ACS) and 1-aminocyclopropane-1-carboxylic
acid oxidase (ACO) genes showed that sugar and acid
composition/accumulation are not exclusively under the
control of ethylene (Dandekar et al., 2004). In banana
fruit, accumulation of sugar after propylene treatment
was not inhibited by 1-MCP once the ripening process
had been initiated (Golding et al., 1998), and in the can-
taloupe melon, suppression of the ACO gene did not in-
hibit sugar accumulation and loss of acidity, indicating
that both ethylene-dependent and -independent regula-
tion coexist during climacteric fruit ripening (Pech
et al., 2008).
Sensitivity to low temperature reflects cultivar differ-
ences in kiwifruit
In previous studies, it has been demonstrated that
different kiwifruit cultivars exhibit varying storability
during low temperature storage. ‘Sanuki Gold’ and
‘Rainbow Red’ kiwifruit are known to be highly perish-
able with a storage potential of only 1–2 months even at
low temperature (Mworia et al., 2012; Nishiyama,
2007). Conversely, ‘Hayward’ kiwifruit are renowned
for their longer storage potential of about 4–6 months
(Pranamornkith et al., 2012). In the present study,
‘Rainbow Red’, ‘Sanuki Gold’, and ‘Hayward’ kiwi-
fruit exhibited cultivar differences in ripening pattern
during storage at 0, 5, 10, 15, and 20°C. ‘Rainbow Red’
and ‘Sanuki Gold’ fruit exhibited a faster reduction in
firmness without any ethylene production during stor-
age at 5, 10, and 15°C reaching the lowest firmness
within 4 weeks compared to fruit at 0 and 20°C (Fig. 2).
On the other hand, ‘Hayward’ fruit softening was faster
at 5 and 10°C compared to fruit at 0, 15, and 20°C.
Thus, our results suggest that the major difference be-
tween the highly perishable cultivars (‘Rainbow Red’
and ‘Sanuki Gold’) and the more hardy cultivar
(‘Hayward’) is the response to a 15°C storage tempera-
ture. ‘Rainbow Red’ and ‘Sanuki Gold’ fruit stored at
15°C ripened faster than fruit stored at 20°C, whereas
‘Hayward’ fruit stored at 15°C showed a delayed ripen-
ing pattern similar to that of fruit stored at 20°C.
Furthermore, the softening of ‘Hayward’ fruit at 5 and
10°C took a longer time of 8 weeks compared to only 4
weeks exhibited by ‘Rainbow Red’ and ‘Sanuki Gold’
at 5, 10, and 15°C (Figs. 2 and 3). In commercial pro-
duction, kiwifruit is harvested at the pre-climacteric
stage when fruit softening has not commenced. In
Japan, ‘Sanuki Gold’ and ‘Rainbow Red’ fruit are har-
vested in early October and late September, respective-
ly, when the minimum field temperature is
approximately 15°C. ‘Hayward’ fruit are harvested in
early November when the minimum field temperature
is approximately 10°C. Thus, the present study suggests
that the differences in maturity dates between ‘Rainbow
Red’/‘Sanuki Gold’ fruit and ‘Hayward’ fruit can be at-
tributed to different sensitivities to temperature.
Implications of storage temperature in kiwifruit culti-
vars
Commercially, harvested kiwifruit are usually stored
at low temperatures of about 0–4°C to prolong their
storage life (Arpaia et al., 1987). However, our present
study shows that kiwifruit ripening occurred faster at
lower storage temperatures (5, 10, and 15°C for
‘Rainbow Red’ and Sanuki Gold’ kiwifruit, and 5 and
10°C for ‘Hayward’ kiwifruit) compared to higher stor-
age temperatures. However, it was peculiar that for all
cultivars, fruit ripening was suppressed at 0°C in a sim-
ilar manner to 20°C. The delayed fruit ripening at 0°C
can be attributed to a slowness of response, indicating
that in as much as 0°C provides physiological stimuli to
induce ripening, it also strongly suppresses the metabol-
ic processes of ripening. Arpaia et al. (1986) showed
6W. O. Asiche, O. W. Mitalo, Y. Kasahara, Y. Tosa, E. G. Mworia, K. Ushijima, R. Nakano and Y. Kubo
that in ‘Hayward’, temperature ranging from 0°C to
10°C is a crucial factor that leads to softening in
ethylene-free conditions. Similar conclusions were
echoed by Marsh et al. (2004), who showed that
‘Hayward’ fruit stored at 4 and 10°C softened faster
than fruit stored at 0°C. Our present study shows that
for long-term storage, a temperature of either 0°C or
20°C is most effective in extending storage life with a
reduced ripening rate. However, the high prevalence of
fruit rot at 20°C makes it unsuitable for long-term stor-
age of kiwifruit. Therefore, storage at 0°C seems to be
most effective in delaying ripening and fruit rot, provid-
ing a marked extension of storage life.
Storage at 5 and 10°C provided ripe, edible fruit
within 4 and 8 weeks in ‘Rainbow Red’ and ‘Sanuki
Gold’ respectively without ethylene production.
‘Hayward’ fruit can be stored for more than 8 weeks at
low temperature since the fruit were firmer with high
acidity even after 8 weeks at 5 and 10°C. Since con-
sumer preference for kiwifruit is based on fruit firm-
ness, SSC, and acidity, ethylene treatment is usually
performed after storage to ensure fruit show uniform
ripening characteristics before being brought to market
(Boquete et al., 2004; MacRae et al., 1990). The present
study shows that for ‘Rainbow Red’ and ‘Sanuki Gold’
fruit, 5 or 10°C can be recommended for storage peri-
ods of 4 or 8 weeks without ethylene treatment before
shipping.
In conclusion, our results show that the ripening rates
of kiwifruit cultivars are modulated by storage tempera-
ture. Furthermore, kiwifruit sensitivity/response to low
temperature is closely related to differences in the stor-
age potential of the cultivars at low temperature and
how early or late the fruit matures on the vine.
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8W. O. Asiche, O. W. Mitalo, Y. Kasahara, Y. Tosa, E. G. Mworia, K. Ushijima, R. Nakano and Y. Kubo
... La maturation des fruits après la récolte est contrôlée par les conditions de conservation telles que la température, l'humidité et le temps de conservation (Singh et al., 2013;FAO, 2018). Les faibles températures permettent de ralentir les métabolismes et ainsi de conserver les fruits plus longtemps tout en retardant au maximum l'apparition de la crise climactérique (Asiche et al., 2017;Gill et al., 2017b;Alkan & Kumar, 2018). La récolte va forcer les mangues à mûrir en créant un stress provoquant des effets proches de la crise climactérique. ...
... Enfin des traitements de température ont été utilisés lors de la conservation. Ces traitements ont été choisi pour valider les effets connus de la température sur la qualité des fruits (Asiche et al., 2017;Gill et al., 2017a) tout en simulant des scénarios de conservations réels. ...
... The cold storage temperature of 12 • C slightly slowed down the hydrolysis of starch and the accumulation of sucrose compared to the fruits stored at 20 • C, but without completely stopping them. The same effect of cold storage temperature was observed in banana fruits (Der Agopian et al., 2011;Peroni-Okita et al., 2013), kiwifruits (Asiche et al., 2017) and melon fruits (Wu et al., 2020). Pulp acidity, pulp colour, and fruit respiration were more strongly affected by the temperature of storage. ...
Thesis
Cette thèse s’inscrit dans le cadre d’un projet initié au CIRAD en 2000 (Lechaudel et al. 2004, Nodey et al. 2014) pour l’amélioration de la qualité des mangues Cogshall produites à la Réunion. Cette étude a été construite autour de l’analyse des pratiques agronomiques et de conservations sur la qualité de la mangue tout au long du continuum entre le pré et le post-récolte afin d’identifier des leviers d’amélioration de la qualité des mangues Cogshall. Trois approches complémentaires ont été réalisées lors de ce travail. La première approche a été une étude expérimentale centrée autour de l’évolution de la qualité des fruits en fonction des pratiques agronomiques (rapport feuilles/fruits), des dates de récolte et des conditions de conservation (température et temps de conservation). La qualité a été évaluée en utilisant des indicateurs de maturité (respiration et émissions d’éthylène), de qualité physique (poids frais, poids sec, couleur, etc.) et de qualité gustative (concentrations des sucres, acidité, etc.). Les résultats ont montré l’importance de la relation source-puits entre le fruit et le rameau sur la croissance. De plus, la qualité à la récolte détermine en grande partie la qualité potentielle des fruits en conservation. La récolte induit la maturation de tous les fruits récoltés. Les pratiques de conservation sont alors utilisées pour contrôler et optimiser cette maturation après la récolte. La deuxième approche a été construite pour étudier les variations des sucres dans les fruits au travers d’un modèle mécaniste. Ce modèle a été calibré en utilisant des données existantes (Lechaudel et al., 2005b ; Joas et al., 2009) et les données récoltées lors de l’approche expérimentale. Ce « modèle sucres » simule les variations des 4 sucres majeurs (amidon, sucrose, fructose et glucose) durant la croissance et la maturation sur l’arbre ainsi qu’en chambre froide. Cette approche a suggéré une forte importance, en pré-récolte, des métabolismes de synthèse de l’amidon et du saccharose. Alors qu’en post-récolte, les flux les plus important seraient ceux responsable de la synthèse du saccharose, de la dégradation de l’amidon ainsi que le flux représentant transformation des molécules de glucose en molécules de fructose. La troisième approche a utilisé un modèle « mangue virtuelle » pour identifier des pratiques agronomiques et de conservation potentiellement avantageuse pour améliorer la qualité des fruits. Le modèle « sucre » a été ajouté aux modèles de croissances existants (Lechaudel et al., 2005a, 2007). Ce couplage de modèle a été ensuite adapté pour estimer la perte en masse des fruits lors de la phase de conservation. Le modèle « mangue virtuelle » a été utilisé pour simuler les évolutions de la qualité en fonction de multiples scénarios possibles de pratiques culturales et de conditions de conservation. Ces simulations appuient l’importance des conditions de croissance et de la date de la récolte sur la qualité des fruits observées dans les analyses expérimentales. Des conditions non-limitantes (bonne irrigation et exposition lumineuse avec une charge en fruit raisonnable) permettraient d’obtenir la meilleure qualité possible. Les dates de récolte ainsi que les pratiques de conservation seraient alors sélectionnées en fonction des conditions de croissance et des marchés souhaités. Les récoltes tardives sont adaptées pour une vente locale avec des fruits de bonne qualité mais avec un temps de conservation court. Alors que des récoltes précoces assurent des durées de conservation longues au prix d’une légère diminution de la qualité des fruits à maturité. Même si le modèle « mangue virtuelle » ne permet de prédire que quelques indicateurs de qualités lors de la croissance et de la maturation des mangues. L’ensemble des analyses et des modèles produits se présentent comme des outils pertinents pour l’étude et le pilotage de l’élaboration de la qualité des mangues tout au long du continuum pré- et post-récolte.
... [13,14] Adequate postharvest ripening could preserve the shelf quality after transferring from cold storage by reducing the ethylene release rate, increasing the antioxidant enzymatic activity, and maintaining the reactive oxygen metabolism balance. [15] Early work suggested that fruit softening, SSC increase, and decrease in titratable acidity (TA) occurs faster in fruit at 5°C, 10°C, or 15°C compared with 0°C and 20°C in the absence of any detectable ethylene, and up-regulates AdACO1, AdACO2, AcACO3, AdETR2, AdETR3, AcMADS2, AcNAC3, and AcNAC5, [3,8,[16][17][18] and restores levels of aroma-related esters before ripening after cold storage (1.5°C) for two or 4 months. [19] Ethylene inhibitor 1-methylcyclopropene (1-MCP) is commonly used to inhibit climacteric fruit ripening. ...
... [22][23][24] 1.0 μL L −1 of 1-MCP delayed kiwifruit softening and prolonged storage to 180 d at 0°C. [25] However, 1-MCP treatment could not inhibit the low temperature-modulated fruit ripening during lowtemperature storage independent of ethylene. [17,[26][27][28] Our previous study found there were significant differences in nutritional components and their changes in different parts of kiwifruit postharvest. Nutrients were metabolized and transferred to different parts during postharvest ripening, affecting the quality of kiwifruit. ...
... Kiwifruit is a typical climacteric fruit, and ripening is induced by ethylene or low temperature. [6] During storage at low temperature (≤15°C), although ethylene was not detected during the softening process of kiwifruit, [17,26] ripening related genes, including AcACS1, AcACO2, AcACO3, AdETR2, and AdETR3, were significantly up-regulated. [8,27,28] Furthermore, low concentration of ethylene (0.01 ml L −1 ) promotes fruit softening and shortens shelf life in commercial storage, [9,10] which suggests that ethylene plays an important role in kiwifruit ripening. ...
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... However, it was shown that even though some preservation techniques significantly prolonged the storage period, they affected the aroma quality, and even led to the direct fruit deterioration instead of normal ripening and softening (Moya-Leon et al. 2006;Zhang and Chen 2014). Related studies showed that LTS delayed the decrease in fatty acids contents and reduced the activities of LOX, HPL, ADH and AAT in kiwifruit, indicating that low temperature had an impact on the content of precursors and the activity of key enzymes in fatty acid metabolism (Asiche et al. 2017). LST reduced the aroma quality of banana and inhibited the expression of the genes (MaHPL, MaLOX and MaAAT ) related to aroma synthesis (Zhu et al. 2018). ...
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... Keywords: Brix acid ratio, Ethylene treatment, Kiwifruit, Ripening quality, Storage temperature 가식 단계까지 참다래를 균일하고 빠르게 후숙시킨다는 장점을 갖고 있다 Shin, 2018 (Antunes, 2007;Shin, 2018;Asiche et al., 2017;Shin, 2018). (Stec et al., 1989;Park et al., 2017;Wang et al., 2018 적정 산도는 세 품종 모두 후숙 기간이 길어짐에 따라 감소하는 경향을 나타내었다 (Fig. 3). ...
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In this study, green ‘Hayward’, gold ‘Haegeum’, and red ‘Hongyang’ kiwifruit cultivars were treated with 50 and 100 ppm ethylene in commercial packing boxes to investigate the postharvest ripening quality during the storage at 10°C and 25°C. As the ripening period proceeded, all three cultivars showed a gradual decreasing trend in firmness and titratable acidity (TA), whereas total soluble solids (TSS) content and Brix acid ratio (BAR) showed an increasing trend. In the case of storage at 25°C, the firmness of ‘Haegeum’ and ‘Hongyang’ ranged from 3.94 to 4.61 N and 4.94 to 5.00 N on the 2nd day at 50 and 100 ppm ethylene, respectively. However, ‘Hayward’ maintained firmness (5.67–7.57 N) up to the 4th day of ripening. In the case of storage at 10°C, there was no significant difference between the control and ethylene treatments. Regarding TSS, all three cultivars showed increasing trends as the ripening period increased, regardless of storage temperature and ethylene concentration, and there was a significant difference between the control and ethylene-treated groups throughout the ripening period at 25°C. The TA of ‘Hayward’ showed the largest difference between the control and treatment as compared to ‘Haegeum’ and ‘Hongyang’ at 25°C. On the 6th day of ripening, the TA of ‘Hayward’ was 1.53 and 0.31 mg/100 g-1 in the control and 50 ppm ethylene treatment, respectively. In contrast, there was no significant difference between the control and ethylene treatments in ‘Hayward’ and ‘Haegeum’ at 10°C. The BAR showed increasing trends in all three cultivars as the ripening period increased. In particular, ethylene-treated ‘Hayward’ and ‘Haegeum’ showed high BAR values of 35.2 and 44.3, respectively, on the 6th day at 25°C. In addition, firmness, TSS, and TA showed significant correlations (r = -0.54, 0.65, and -0.83, respectively) with BAR. Generally, the effect of ethylene treatment at 10°C was less than at 25°C, which may be due to the low metabolic rates of the fruits at low temperatures. In addition, there was no significant difference in quality with the change in ethylene concentration because the external ethylene could no longer influence the ripening process once fruit ripening was initiated and the internal ethylene concentration reached saturation levels. Taken together, based on firmness, TSS, TA, and BAR, consumers’ preferences for ‘Hayward’ were not met at 10°C until the 6th day of ripening, but at 25°C, consumers’ preferences were attained after the 4th day. In the case of ‘Haegeum’ and ‘Hongyang’, consumers’ preferences were attained starting from the 2nd day of ethylene treatment in both 10°C and 25°C conditions.
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Near eating-stage fruit of ‘Hayward’ and ‘Qihong’ kiwifruit (firmness 20 N) were treated with 0.5 µL L ⁻¹ 1-Methylcyclopropene (1-MCP) for 12 h at room temperature (23 ±1 °C), and then stored at 23 ± 1 °C for several days. Compared with control fruit, 1-MCP greatly delayed loss of firmness, and extended the room-temperature shelf life of ready-to-eat kiwifruit by an extra 8 d (‘Hayward’) or 10 d (‘Qihong’). The 1-MCP treatment also slowed the declines in titratable acidity and color, but had no significant effects on soluble solids content (p < 0.05). Although in the 1-MCP treated fruit the amounts of total volatiles increased during room-temperature storage, the concentration of total volatiles was lower in the treated fruit compared with the untreated controls. Treatment with 1-MCP inhibited ester production and aldehyde degradation. At edible firmness, kiwifruit treated with 1-MCP showed similar fruit quality compared with the untreated controls, with similar mean values in soluble solids content, titratable acidity and color (p > 0.05). 1-MCP also decreased ethylene production and respiration rate. Moreover, the activities of superoxide (SOD), catalase (CAT) and peroxidase (POD) were increased in the treated fruit compared with the controls. The results indicate treatment with 1-MCP is a potentially effective way of prolonging the room-temperature (23 ± 1 °C) shelf life of ready-to-eat kiwifruit and maintaining their eating quality under commercial conditions.
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Enzyme-based time–temperature integrators (TTIs) were applied to indicate the ripeness of plastic-container-packaged kiwifruit. The hypothesis was that the ethylene gas production, an indication of kiwifruit ripeness, depends on the time–temperature history. The market-purchased, unripe kiwifruit was assumed to be stored in a plastic container to ripen at home, as common practice in Korea. The kinetics of ethylene gas production and TTI color change was found to be suitable for the indication. The Arrhenius activation energy (Ea) of the ethylene gas production and color changes of lipase-, amylase-, and laccase-based TTIs were 41.60 ± 10.87 kJ/mol, and 42.76 ± 9.57, 100.28 ± 6.84, and 30.49 ± 4.41 kJ/mol, respectively. Kiwifruit firmness was also tested as a practical, major quality factor. The Ea of the firmness changes was 39.66 ± 4.64 kJ/mol. In scenarios tests, the firmness could be most accurately predicted from the lipase-based TTI color. Overall, the lipase-based TTI was found to be the best in terms of the similarity of the Ea and the prediction accuracy. Practical Application Currently, there is no commercially available indicator that can determine the ripeness of packaged kiwifruit. Although an ethylene gas indicator is possible, it has been difficult to commercialize because the gas may leak in the package. An indicator on plastic containers with kiwifruit, as is common in Korea, has been developed using a conventional time–temperature integrator (TTI). The hypothesis was that the production of ethylene gas, indicating kiwi ripening, is also dependent on the time–temperature history. It was found that the TTI color change over time was suitable for judging suitable kiwifruit hardness, a major kiwifruit ripeness index.
Article
The commonly accepted kiwifruit harvest index based solely on soluble solids content (SSC) has lost its original significance owing to the increased sophistication of marketing coupled with the commercialisation of new cultivars, many with yellow flesh when ripe. The precision of novel harvest indices may be improved by a molecular understanding of fruit maturation changes in commonly monitored fruit attributes, including SSC, flesh colour and firmness. Transcriptional changes in the early-maturing Actinidia chinensis var. chinensis ‘Zesy002’ and later maturing A. chinensis var. deliciosa ‘Hayward’, grown at a single site, have been quantified weekly in the period leading up to and past the commercial harvest period. Transcriptomic data highlighted numerous maturation related changes in the fruit, and differences between the two cultivars. Examples of gene changes of relevance for non-structural carbohydrates included the large sub-unit 4 of ADP-glucose pyrophosphorylase (APL4) indicative of starch synthesis, BETA AMYLASE 3.2 (BAM3.2) for starch breakdown and the sugar transporter (SWEET9a). The association between STAYGREEN2 (SGR2) with flesh degreening was strong in ‘Zesy002’, although a later increase in ‘Hayward’ to levels similar to those in ‘Zesy002’ was not accompanied by an equivalent flesh colour change. In ‘Zesy002’ there were numerous individual cell wall gene changes associated with the change to rapid softening, including EXPANSIN7 (EXP7), POLYGALACTURONASE1 (PG1), PECTATE LYASE (PL), PECTIN METHYL ESTERASE (PME) and XYLOGLUCAN TRANSGLYCOSYLASE/ HYDROLASE (XTH). However, among these genes, it is possible to see similar changes in ‘Hayward’ which were not associated with a marked change in softening rate, including for EXP7 and PG1. The most obvious start points for changes in transcription of these genes were the seed coat colour change, the cessation of growth, and the change to ripening (rapid softening and starch breakdown). The findings are discussed with respect to fruit maturation and the possible use of gene markers as harvest indices.
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Kiwifruit may be stored for prolonged periods at low temperatures during which time the fruit continue to ripen slowly and dehydration occurs. Abscisic acid (ABA) plays important roles in both fruit ripening and environmental stress response, including dehydration. To investigate the inter-relationships among postharvest dehydration, ethylene production, ABA and fruit ripening, two independent experiments were undertaken with ‘Hayward’ kiwifruit. Water loss was manipulated by holding fruit in three environments of different humidities at 20 °C for up to 6 d, and at 0 °C for up to 16 weeks. The impacts of the treatments over time after harvest were investigated on fruit softening, ABA content and ethylene production, and on the expression of genes of the ABA biosynthetic pathway and ethylene metabolism. Water loss induced earlier ethylene production and accelerated softening late in storage. However, these changes were not directly related to increased ABA content. The strongest association seen was between tissue ABA content and fruit firmness, irrespective of the degree of water loss. In conclusion, it is suggested that the accelerated softening of ‘Hayward’ kiwifruit caused by dehydration may be mediated via ethylene, but that the precise role for ABA, either directly or indirectly, is as yet difficult to ascribe.
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This work aimed to offer a non-destructive and fast approach to visualizing the soluble solids content (SSC) and acidity (pH) of the whole kiwifruit. Most of the visible-near-infrared spectral imaging techniques used in postharvest fruit and vegetables assessment exhibit issues related to the identification of the quality spatial distribution within intact samples, mainly due to sampling surface curvature effects. Here, a push-broom-type NIR hyperspectral imaging camera and a sample rotation stage were combined to scan entire kiwifruit surfaces. Then, key wavelengths in the range of 1002–2300 nm were extracted for constructing SSC and pH calibration models by partial least squares regression analysis. The resulting SSC prediction accuracy was sufficiently high: the coefficient of determination (R2cv) and the root mean square error (RMSEcv) of cross-validation set were 0.74 and 0.7 %, respectively. For pH, the R2cv and RMSEcv were 0.64 and 0.14, respectively. Finally, the SSC and pH 360˚mapping results surpassed earlier works in this area that they showed a distinct spatial distribution within each intact sample. It was concluded that the proposed object rotation hyperspectral imaging approach is promising for the non-destructive prediction mapping of SSC and pH in kiwifruit or other cylindrical-shaped samples.
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In order to extend the “eating window”, the optimum ripening phase suitable for eating, the combination of treatment with propylene (an ethylene analog) and 1-methylcyclopropene (1-MCP; an ethylene inhibitor) was assessed in three kiwifruit cultivars: ‘Rainbow Red’ Actinidia chinensis, ‘Sanuki Gold’ A. chinensis, and ‘Hayward’ A. deliciosa. Propylene treatment initiated the ripening process by inducing fruit softening, increasing soluble solid content (SSC), and decreasing titratable acids (TA), with or without endogenous ethylene production, depending on the duration of exposure. Once endogenous ethylene was induced, it accelerated fruit ripening, resulting in an over-ripening phase and shortening of the “eating window”. ‘Rainbow Red’ and ‘Sanuki Gold’ fruit treated with propylene continuously or for 48 h initiated endogenous ethylene production that led to an “eating window” lasting only 2 days (range of 3–5 days after the start of treatment), whereas it lasted for 7 days (range 3–10 days) in ‘Hayward’ fruit. Limited propylene treatment of the three cultivars for 24 h induced ripening without the detection of ethylene production, suggesting that the optimum ripening phase suitable for eating can be attained without endogenous ethylene production, resulting in a longer “eating window”. ‘Rainbow Red’ and ‘Sanuki Gold’ fruit treated with propylene for 48 h followed by 1-MCP treatment had extended “eating window” and shelf-life, with the suppression of endogenous ethylene. These results illustrate the practicability of different durations of propylene treatment in facilitating kiwifruit ripening and the additional benefit of 1-MCP treatment to the extend shelf-life of new high-quality kiwifruit cultivars, ‘Rainbow Red’ and ‘Sanuki Gold’.
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'Galia' (Cucumis melo var. reticulatus L. Naud. 'Galia') melons exhibit relatively short postharvest longevity, limited in large part by the rapid softening of this high quality melon. The present study was performed to characterize the physiological responses of 'Galia' fruit harvested at green (preripe) and yellow (advanced ripening) stages and treated with 1-methylcyclopropene (1-MCP) before storage at 20°C. Treatment with 1.5 μL·L-1 1-MCP before storage delayed the climacteric peaks of respiration and ethylene production of green fruit by 11 and 6 d, respectively, and also significantly suppressed respiration and ethylene production maxima. Softening of both green and yellow fruit was significantly delayed by 1-MCP. During the first 5 d at 20°C, the firmness of green control fruit declined 66% while 1-MCP-treated fruit declined 46%. By day 11, firmness of control and 1-MCP-treated green fruit had declined about 90% and 75%, respectively. The firmness of control yellow fruit stored at 20°C declined 70% within 5 d while 1-MCP-treated fruit declined 30%. The 1-MCP-induced firmness retention was accompanied by significant suppression of electrolyte leakage of mesocarp tissue, providing evidence that membrane dysfunction might contribute to softening of 'Galia' melons. The mesocarp of fruit harvested green and treated with 1-MCP eventually ripened to acceptable quality; however, under the treatment conditions (1.5 μL·L -1 1-MCP, 24 h) used in this study, irreversible suppression of surface color development was noted. The disparity in ripening recovery between mesocarp versus epidermal tissue was considerably less evident for fruit harvested and treated with 1-MCP at an advanced stage of development. The commercial use of 1-MCP with 'Galia'-type melons should prove of immense benefit in long-term storage and/or export situations, and allow for retention of quality and handling tolerance for fruit harvested at more advanced stages of ripening.
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Kinetic models describing softening during storage of 'Hortl6A' kiwifruit at different temperatures are useful tools for the development of pre-conditioning and ripening protocols. Magness-Taylor firmness, compression firmness, and stiffness were assessed for their usefulness as tools to monitor and predict softening of 'Hortl6A' kiwifruit during storage at six storage temperatures ranging from 1.5 ° C to 25 ° C. Softening showed the same general biphasic pattern for all three measures, similar to that for green 'Hayward' kiwifruit, and could be described using simple exponential decay models. Magness-Taylor firmness reached an asymptotic minimum rapidly, whereas compression firmness and stiffness still decreased measurably at the end of storage. The rate of softening increased with temperature, and the biphasic pattern of the softening curves became more pronounced with later harvest dates. The effects of orchard, cane, and fruit position on parameter estimates such as rate constant, activation energy, and asymptotic firmness value, were negligible.
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Premature softening limits storage life of kiwifruit at 0°C. Exogenous ethylene induces rapid softening at 20°C and at 0°C and a concentration of 0.01 ul/L will enhance softening at 0°C. The influences of low temperature, an ethylene synthesis inhibitor (AVG) and application of ethylene at different maturities, were investigated to elucidate ethylene's role in initiating kiwifruit softening. Fruit response to ethylene became more pronounced and fruit softened more as maturity advanced. Exposing fruit to 0°C for 2-9 weeks hastened ethylene production compared with fruit maintained at 20°C continuously after harvest. However, fruit softening occurred without changes in ethylene production, ACC concentration or ACO activity. AVG treated fruit softened slightly more slowly and had lower ACC concentrations, ACO activity and ethylene production than control fruit, both at 20°C and after 2 months at 0°C. Kiwifruit softened from about 90 N to 12 N when endogenous ethylene production was low (below 0.2 ul/kg/h) and constant; we suggest that this is System 1 ethylene production. Increased ethylene production (System 2?) only occurred as fruit softened from 12 N to eating ripe (6-8 N), suggesting that kiwifruit become more sensitive to ethylene with time during maturation and at 0°C, possibly because ethylene receptors become more sensitive or more numerous.
Chapter
Ethylene plays a crucial role in ripening of kiwifruit, and the elucidation of the controlling factors in ethylene biosynthesis is important in prolonging the storage life and keeping the fruit quality during the handling operations.
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The effect of 1-MCP prestorage treatment was studied during short, medium and long term cold storage with subsequent exposures at 20 °C (shelf-life) on ethylene and CO2 production, softening, soluble solids contents, titratable acidity, color and decay of ‘Hayward’ kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang et A.R. Ferguson). Application of 1-MCP suppressed or decreased ethylene production during shelf-life at all storage periods. Also, 1-MCP reduced CO2 production during shelf-life after medium and long term cold storage. Application of 1-MCP significantly delayed the softening of kiwifruit at 20 °C for 14 days, after short and medium term cold storage, with no affect during shelf-life after long term cold storage. 1-MCP did not affect soluble solids contents, and during shelf-life after short and medium term cold storage, titratable acidity was higher for 1-MCP treated fruit. 1-MCP also delayed decay development caused by Botrytis cinerea and changes in the flesh color parameters lightness and chroma during shelf-life.