全 文 ：Received 8 Jan. 2003 Accepted 26 Apr. 2004
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Acta Botanica Sinica
植 物 学 报 2004, 46 (8): 928-934
Effects of Temperature and Atmosphere Component on
Quality of Stored Jujube Fruit
LIN Li, TIAN Shi-Ping*, WAN Ya-Kun, XU Yong, YAO Hong-Jie
(Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany,
The Chinese Academy of Sciences, Beijing 100093, China)
Abstract: Jujube (Ziziphus jujuba Mill. cv Dongzao) fruit was stored under controlled atmospheres (CA)
of 5% O2 plus 0% CO2, 10% O2 plus 0% CO2, or dynamic CA (70% O2 +0% CO2 for 7 d, followed by
transferring to 5% O2) at -1 °C, or in air at 25 °C and -1 °C, respectively, and then determined disease
incidence, contents of pigment, total soluble solids, titratable acidity, ethanol and ethyl acetate in storage
periods. The results indicated that the contents of ethanol, ethyl acetate and the degradation of anthocyanin,
and chlorophyll were significantly lower in the fruit stored in CA at -1 °C than those in air at -1 °C. Short
term high O2 (70%) treatment was the most effective in maintaining peel color, anthocyanin and chlorophyll
contents and preventing peel browning compared to other treatments. Ethanol content was significantly
low in the fruits stored in CA with 10% O2 plus 0% CO2 while storage of CA (5% O2 plus 0% CO2)
concentration was effective in reducing ethyl acetate content throughout the storage period. CA
conditions effectively controlled disease development of jujube fruit. Soluble solid content (SSC) and
titratable acidity were however not significantly affected by CA treatments.
Key words: jujube fruit; controlled atmosphere; color; volatile substance; decay rate
Jujube (Ziziphus jujuba), a highly nutritional value and
attractive fruit, is grown commercially in China. Although
the fruit can be stored at low temperature for two months,
they are very perishable being highly susceptible to
postharvest color fading, browning, decay, and water loss
(Tian, 2000). Controlled atmosphere (CA) storage at low
temperature had beneficial effects on various pathological
and physiological problems of fruits occurring during stor-
age (Ke et al., 1990; Tian et al., 1996; Rogiers and Knowles,
2000). Short term treatment with ultra low oxigen (ULO) or
high CO2 concentrations could be effective in controlling
decay (Beaudy, 1999; Tian et al., 2001). However, Day (1996)
found that high O2 concentration played a major role in
preventing browning and inhibiting decay of postharvest
fruits and vegetables. In a previous study, we found that
CA significantly reduced decay, prevented peel browning
and extended storage life of longan fruit (Tian et al., 2002).
There are no published data on the effects of high or low
O2 atmospheres on physiology, quality and storability of
jujube fruit. The objective of the present study was mainly
to investigate the effects of different temperatures and at-
mospheres on colour, flavor, decay and storability of ju-
jube fruit during storage periods.
2 Materials and Methods
2.1 Fruit and storage conditions
Jujube (Ziziphus jujuba Mill. cv Dongzao) fruit with
commercial maturity and uniform size was harvested from a
commercial orchard in Bingzhou, Shandong Province in the
early October. The fruits were precooled immediately after
harvest, then transported to Beijing in a refrigerated van at
10 °C for about 6 h, sound and disease free fruit was col-
lected and treated as follows: CA conditions at –1 °C, in-
cluding CA-Ⅰ, 70% O2 + 0% CO2 for the first 7 d and subse-
quently transferred to 5% O2 + 0% CO2; CA-Ⅱ, 5% O2 +
0% CO2; CA-Ⅲ, 10% O2 + 0% CO2, and in air at 25 °C and
–1 °C.
Controlled atmosphere cabinets (105 cm×55 cm×100
cm), with CO2 and ethylene absorbers, were linked with an
atmosphere analyzer (FC-701, N. Copernico, Italy). Initial
O2 and CO2 levels in the cabinets were established by a
flow-through system, mixing N2 (100%) and O2 (99.5%) via
pressure regulators, through automatically controlled and
regulated by the analyzer. There were three replicates with
50 kg of fruit per replicate in each CA cabinet with approxi-
mately 95% RH at –1 °C.
LIN Li et al.: Effects of Temperature and Atmosphere Component on Quality of Stored Jujube Fruit 929
There were four boxes, each containing 20 kg fruits,
enclosed in plastic film bags (0.04 mm) at –1 °C, and other
two boxes at 25 °C for control. Fruits in all treatments were
analyzed in different intervals according to the experiment
design.
2.2 Disease incidence and decay score
Disease incidence was monitored by recording the per-
centage showing visible symptom of disease on the fruit
surface. Decay score was evaluated subjectively as follows:
none (no decay), slight (one to three small spots of decay),
moderate (one-quarter to one-half of fruit decayed) or se-
vere (one-half to full fruit decayed). Three replicates of 20
fruits were used for each treatment at different storage time.
2.3 Colour
External colour was measured on opposite sides of the
fruit using a Minolta chromameter (model CR-100/CR-110;
Minolta, Ramsey, NJ) which provided CIE L*, a* and b*
values. These values were used to calculate chroma (C*=
(a*2+b*2)1/2), which indicates the intensity or colour
saturation, and hue angle (ho = arctangent (b*/a*)). Fruit
turning red was defined as: red area extending to the middle
of the fruit. Fifteen fruits with three replicates were assessed
for each treatment at different storage time.
2.4 Chlorophyll and anthocyanin concentrations
The anthocyanin concentration of fruit skin was deter-
mined according to the modified method of Paull et al.
(1985). Skin tissue was taken from the equatorial surface of
each jujube fruit, and 6 g of the tissue was blended for 30 s
in a blender (Waring CN, No. 34BL97) at a moderate speed
with 50 mL of 1% HCl-MeOH. The homogenate was filtered
and the absorbance of 10 mL filtrate was immediately read
at 535 nm on a UV-160 spectrophotometer (UV-160A;
Shimadzu Scientific Instrument, Japan). The results were
reported as absorbance measurements. Chlorophyll con-
tent was determined using N, N-dimethylformamide (Moran,
1982). Three replicates with fifteen fruits each were used at
different storage time.
2.5 Titratable acidity (TA) and soluble solid concentra-
tion (SSC)
TA was determined by potentiometric titration with 0.1
mol/L NaOH up to pH 8.1 using 1 mL of diluted juice in 25
mL distilled H2O. The results were expressed as percent
citric acid. SSC was determined using an Abbe refractome-
ter (10481 S/N, USA). The number of replicate and fruit was
the same as in 2.4.
2.6 Volatile compounds
Contents of ethanol and ethyl acetate in fruit were de-
termined by head space gas chromatography (Shimadzu,
GC-9A, Japan), as described by Tian et al. (1996). Fruit
sample of about 100 g was put in an Omni-mixer (Omni
International Inc., Waterbury) and an equal amount of 20%
trichloroacetic acid was added, the mixture then was ho-
mogenized for 2 min in an ice water bath. A 5-g sample of
the mixture was sealed in a 10-mL vial and then incubated at
40 °C for 60 min. A 0.5-mL head space gas was sampled by
syringe and injected into the gas chromatograph equipped
with a flame ionization detector (FID) and glass column (2
mm×4 m). The determinations were conducted at: 85 °C
oven temperature, 130 °C injector temperature and 250 °C
detector temperature. The components were identified in-
dividually by comparing retention time against standards,
concentrations being determined by a regression equation
calculated on four samples of standard concentrations.
There were three replications for each analysis.
2.7 Statistical analysis
The data were analyzed by analysis of variance as a
one-factor general linear model procedure (ANOVA). The
treatment means were separated at 5% significant level with
Duncan’s multiple range tests. Differences at P ≤ 0.05 were
considered to be significant.
3 Results
3.1 Disease incidence
As shown in Fig.1, disease development in jujube fruit
increased as the period of storage extended. After 60 d of
storage, about 60% of the fruit stored in air at –1 °C had
begun to rot. Fruit stored in CA had significantly lower
infection rate than those in air. However, disease develop-
ment significantly increased as storage extended to 80 d.
After 60 d of storage at –1 °C, only slight decay was ob-
served from jujube fruit stored in air, whereas fruit from all
CA conditions had minimal decay. Among three CA
conditions, treatment with 10% O2 at –1 °C had the lowest
decay score.
3.2 Peel colour
Jujube fruit stored in air at 25 °C turned red rapidly and
the rate of turning red increased quickly from 30% at har-
vest to 80% after 3 d of storage. Similar results but less
extreme, were observed in fruit stored at low temperature or
in CA (Fig. 2). The colour of jujube fruit stored in air at 25 °C
became darker (low L* values), less vivid (low C* values)
and tended to be red (low H values) with increased storage
time. Similar trends were observed in jujube fruit stored at
–1 °C (Fig.3). In contrast, the colour of jujube fruit treated
with high O2 atmosphere tended to be brighter (higher L*
values), more vivid (higher C* value) and less red (higher H
angle) in colour than the other treatments in the storage
period. High O2 treatment resulted in maintenance of higher
Acta Botanica Sinica 植物学报 Vol.46 No.8 2004930
L* values, indicating lower skin browning in jujube fruit as
compared with the other treatments.
3.3 Chlorophyll and anthocyanin degradation
The anthocyanin content of the fruit was significantly
affected by storage time. Jujube fruit at harvest had an
anthocyanin absorbance of 4.52 per 100 cm2 peel area at
harvest. The absorbance at 535 nm, with a characteristic of
the anthocyanins, decreased rapidly to 2.27 after 9 d of
storage at 25 °C (Fig.4). Jujube fruit stored in air and CA at
–1 °C also showed a decrease in anthocyanin content. CA
with 70% O2 concentration more effectively maintained an-
thocyanin content as compared with other treatments (P =
0.05). The chlorophyll content of jujube fruit declined quickly
from 45.3 µg/g FW at harvest to 26.9 µg/g FW after 9 d of
storage in air at 25 °C (Fig.4). Low temperature storage sig-
nificantly reduced the decline in chlorophyll of jujube fruit.
In contrast with other treatments, high O2 treatment could
maintain a high chlorophyll content before 60 d of storage,
Fig.1. Disease incidence and decay severity of jujube fruit stored under different conditions. Decay score: 0 = none, 1 = slight, 2 =
moderate, 3 = severe. Vertical bars indicate standard deviations (P = 0.05). Means with the same letter are not significantly different for
individual storage days.
Fig.2. Redding rate of jujube fruit stored under different conditions.Vertical bars indicate standard deviations (P = 0.05). Means with
the same letter are not significantly different for individual storage days.
LIN Li et al.: Effects of Temperature and Atmosphere Component on Quality of Stored Jujube Fruit 931
Fig.3. Changes in external color of jujube fruit stored under different conditions. Vertical bars indicate standard deviations.
Fig.4. Chlorophyll and anthocyanin contents of jujube fruit stored under different conditions. Vertical bars indicate standard deviations.
Means with the same letter are not significantly different at P = 0.05 for individual storage days.
Acta Botanica Sinica 植物学报 Vol.46 No.8 2004932
then the chlorophyll content declined rapidly (Fig. 4).
3.4 Fruit quality
SSC of the fruit kept in air at 25 °C increased gradually
with time, changing from 23.6% at harvest to 31.4% at the
9th day, but there was no significant difference in SSC of
the fruit stored at low temperature and under CA condi-
tions (Fig.5). In addition, titratable acidy content was not
significantly affected by different storage conditions (Fig.
5).
3.5 Volatile compounds
Ethanol contents in the fruit stored in CA with 5% O2 or
10% O2 increased gradually, from 102.17 nmol/g at harvest
to 138.34-132.01 nmol/g after 80 d of storage (Fig.6). The
CA storage with 10% O2 concentration was the most
Fig.5. Changes in soluble solid content and titratable acidity of jujube fruit stored in different conditions. Vertical bars indicate standard
deviations.
Fig.6. Ethanol and ethyl acetate contents of jujube fruit stored under different conditions. Vertical bars indicate standard deviations.
LIN Li et al.: Effects of Temperature and Atmosphere Component on Quality of Stored Jujube Fruit 933
effective in reducing ethanol accumulation among all the
treatments. Ethyl acetate content significantly decreased
in jujube fruit stored in air at 25 °C after 9 d (Fig.6). As for
the fruit, ethyl acetate content of the fruit stored in air and
CA at –1 °C increased gradually with storage time, and then
decreased after 40 and 60 d of storage respectively. Fruit
stored in CA with 10% O2 had a significantly higher ethyl
acetate content than the others after 40 d of storage, and
then decreased rapidly. CA with 5% O2 concentration was
more effective in reducing ethyl acetate accumulation as
compared to other treatments (Fig.6).
4 Discussion
In recent years, high O2 treatment, called “oxygen
shock” or “gas shock”, has been used to treat postharvest
fruit and vegetable because of the beneficial to inhibition
of physiological metabolism, maintenance of quality and
extension of shelf life (Day, 1996; Whitaker et al., 1998;
Fellman et al., 2003). Lu and Toivonen (2000) reported that
exposure of whole “Spartan” apples to 100 kPa O2 for 12 d
at 1 °C before slicing resulted in lower respiration, slower
browning and softening of slices. In the previous research,
CA with high O2 concentration could effectively prevent
longan fruit peel from browning (Tian et al., 2002). This
experiment indicated that short term high O2 treatment was
more effective in maintaining peel colour of jujube fruit in
comparison with other CA treatments and made the fruit
lighter and less intensely red (Fig.3). Anthocyanins are pig-
ments responsible for the red, pink, purple and blue colours
of fruits (Sankat et al., 2000). Fruit owing their colour to the
presence of anthocyanin pigment present particular prob-
lems with respect to colour stability. Skrede (1985) consid-
ered that anthocyanin-containing fruits were susceptible
to colour deterioration from a natural red or purple to a
more dullish brown colour. These results confirmed that
short term high O2 treatment can maintain anthocyanin and
chlorophyll content more effectively by comparing with
other treatments (Fig.4).
Accumulation of ethanol is related to off-flavors in fruit
(Tian, 2000; Tian et al., 2002). Low O2 atmospheres, par-
ticular under ultra low oxygen conditions, have usually re-
sulted in considerable increases in ethanol content in many
fruit (Ke et al., 1990; Tian et al., 1996). However, in this
current experiment we found that the production of these
volatiles varied among jujube fruit under different experi-
mental conditions, indicating different responses of the fruit
to various storage conditions. Short term high O2 treated
jujube fruit maintained the lowest level of ethanol, particu-
larly before 40 d, compared to the fruits in other treatments
(Fig.6). However, after 60 d, high O2 treated fruit accumu-
lated the highest level of ethanol. CA conditions with 5%
O2 plus 0% CO2 or 10% O2 plus 0% CO2 was effective in
reducing volatile production (Fig.6). Especially, CA with
10% O2 treatment more significantly inhibited ethylene evo-
lution (data not shown) and ethanol production and ex-
tended storage life of jujube fruit as compared to other
treatments throughout the experimental period. There are
several possible explanations for the continued increase in
ethanol content in fruit from the high O2 treatments after
removal from the atmospheres. First, the cells may have
adjusted to the high O2 concentration and, upon removal,
the 5% O2 environment was seen as anaerobic. Secondly,
some of the fruit cells may have died as a result of the high
O2 stress, though we did not observe any tissue browning
or other evidence of necrosis. The most accepted explana-
tion for oxygen toxicity is the formation of superoxide
radicals, which are destructive to some aspects of cell me-
tabolism (Fridovitch, 1975).
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