JKAU: Met., Env. & Arid Land Agric. Sci., Vol. 20 No. 1, pp: 3-22 (2009 A.D. / 1430 A.H.)
Effect of Carbon Dioxide-Enriched Atmosphere during
Cold Storage on Limiting Antioxidant Losses and
Maintaining Quality of ‘Barhy’ Date Fruits
D.A. El-Rayes
Department of Plant Production and Protection,
College of Agriculture and Veterinary Medicine,
Qassim University, Al- Qassim, Kingdom of Saudi Arabia
[email protected]
Abstract. Mature ‘Barhy’ date fruits (Phoenix dactylifera L.) were
stored under different storage temperatures (0, 2, 4, 6°C) under
modified atmosphere (MA) conditions with 0.03, 5, 10, or 20% carbon
dioxide concentrations (balance air). Fruit total phenolic content
(TPC), flavonoids content, carotenoids content, total sugar %, SSC %,
and fruit skin color (L*a*b*c* and h*) were determined. Total
phenolic content (TPC) was determined by the Folin-Ciocalteu
method, and antioxidant capacity was determined using ferric
reducing antioxidant power (FRAP). A clear integration was observed
between modified atmosphere and cold storage treatments regarding
maintaining fruit quality during the storage period. Fruits stored under
low temperature conditions (0°C) or relatively high CO2 concentration
(20% CO2) did not show any chilling or CO2 injury symptoms. Fruits
kept under MA conditions with 20% CO2 at cold storage (0°C)
showed brightest yellow color, and highest storage ability among all
stored fruits. All MA conditions investigated extended date storability
by maintaining fruit quality. The effect of MA conditions on
maintaining fruit quality was magnified when fruits were stored under
cold temperature. Fruit quality was maintained for 173 days when
stored in 20% CO2 at 0°C, whereas it did not exceed 60 days when
stored under common air composition (containing 0.03% CO2) at 0°C.
Treatments with high CO2 concentrations (20% CO2) under cold
storage conditions (0°C) maintained fruit total phenolic content,
SSC%, total sugar content, and total tannins.
3
4
D.A. El-Rayes
Keywords: Barhy date fruits, Phoenix dactylifera L., modified
atmosphere, cold storage, fruit quality, total phenolic
content (TPC), antioxidant activity.
Introduction
Date palm is the major fruit tree in most Arabian Gulf countries and it is
widely grown in the middle-eastern countries. ‘Barhy’, one of the most
popular cultivar worldwide, is marketed and consumed at the full mature
stage of development (Bisr or Khalal). However, its economical value
decreases sharply when it ripens as surplus production has to be sold at
lower prices. Some trials have been carried out to maintain fruit quality
during storage of dates, including coating with polypropylene films
(Thompson and Abboodi, 2003), or using polyethylene bags (Attia, et al.,
1997). However, responses to these treatments have been limited.
Temperature is the environmental factor that most influences the
deterioration rate of harvested commodities. Temperature management is
the most effective tool for extending the shelf life of fresh horticultural
commodities (Kader, 2002). Some trials have been carried out to
maintain dates fruit quality during storage by using low temperature
(Hassan and El-Sheemy, 1989 and Hegazy, et al., 2003), however, no
published research are available indicating the optimum storing
temperature for Barhy dates at full mature stage.
The use of elevated CO2 at storage atmosphere for preserving fruit
quality and delaying fruit deterioration has been described (El-Rayes and
Ahmed, 2001; Kader, 2002; and Al-Redhaiman, 2005). Elevated
concentrations of CO2 inhibited decay and retarded softening without
impairing the flavor of many fruits (Kader, 2002). Moreover, CO2
significantly inhibited botrytis in Red Globe table grapes (Carlos, et al.,
2002). Although the effect of modified atmosphere (MA) treatments on
quality preservation of dried date fruit has been studied (Navarro, et al.,
1998), no information about responses of soft fully mature dates is
available.
Interest in phytochemical content and antioxidant activity of fruits
and vegetables has been very high in recent years. Recent studies have
shown that the majority of antioxidant activity in fruits or vegetables may
originate from the polyphenolic compounds (Wang, et al., 1996).
Effect of Carbon Dioxide-Enriched Atmosphere…
5
Date fruits are an excellent source of phenolics and therefore possess
an extremely high antioxidant capacity. The presence of phenolic
compounds in fruits and vegetables has been studied fairly well. In
addition to their important functions in plant defense mechanisms and
external stresses (Wang, et al., 1994), they also affect the quality, color
and taste of fruits and their products like juice and fruit slice (Van der
Sluis, et al., 2002). In low concentration, phenolics may protect food
from oxidative deterioration; however at high concentration, they (or
their oxidation products) may participate in discoloration of foods. For
example, the brown color development (known as enzymatic oxidation)
is mainly due to the polyphenol peroxides (PPO) activity and the amount
of the polyphenol substrates. As shown for apple fruits, the coloration
after oxidation depends on the balance between the phenolics:
hydroxycinnamics, and flavonols (Frankel, 1995).
Flavonoids exist widely in the plant kingdom and are especially
common in leaves, flowering tissues and fruits (Larson, 1988). Plant
flavonoids are an important part of the diet because of their effects on
human nutrition (Frankel, 1995).
Known properties of the flavonoids include: free radical scavenging,
and strong antioxidant activity (Frankel, 1995). Some evidence suggests
that the pharmacological effects of flavonoids are correlated with their
antioxidant activities.
The objective of this study was to evaluate the possibility of using
modified atmosphere conditions with high carbon dioxide-enriched under
relatively low temperature to maintain fruit quality and extend storage
ability of Barhy date fruits at full mature stage of development.
Materials and Methods
Plant Material
Fifteen years old ‘Barhy’ date palms (Phoenix dactylifera L.)
grown at the Research and Experimental Station, College of Agriculture
and Veterinary Medicine, Qassim University, Buraydah, Al-Qassim, the
Kingdom of Saudi Arabia, were selected for the study. All palms were
mature, of the same age and almost uniform in growth. The palms were
in good physical condition, free from insect damage and diseases and
were subjected to the same horticultural management treatments.
6
D.A. El-Rayes
Fruits were harvested at full mature stage, according to skin color
(the whole fruit should be yellow, and the yellowish green area should
not exceed 10%) and the percentage of soluble solids content (SSC%)
greater than 28% (Hegazy, et al., 2003). Immediately after harvest, fruits
were transported to the postharvest laboratory where those fruits of
similar shape, color, and degree of development were divided into groups
and were wiped free of dirt.
Treatments
Fruits were divided into 16 groups, each group representing a
different treatment. These treatments included four different storage
temperatures (0, 2, 4, and 6 + 2°C), each of storage temperatures was
divided into 4 groups, each group received one of the following CO2
treatments: 5%, 10%, 20% or 0.03% CO2, which represents room
ambient air.
Five replicates of each treatment were stored in well sealed gas
tight glass containers equipped with inlet and outlet valves, and CO2
was injected from gas cylinders to provide concentrations of 5%, 10%,
or 20% CO2 in air. Supply and exhaust CO2 gas composition was
monitored using a gas chromatograph (Carle Analytical series S, NY,
USA).
Analyses
Monthly samples (ten fruits per replicate) were removed and
frozen immediately for determinations of total tannin, sugars (total,
reducing and non-reducing), and SSC% contents. Each treatment was
terminated when the number of ripe fruits in each spike exceeded the
number of the unripe fruit.
SSC% was measured with a temperature compensated RFM 110
Bellingham + Stanley LTD refractometer (Lawrenceville, GA, USA).
Reducing and non-reducing sugars were determined colorimetrically
according to Dubios, et al. (1956) using Perkin Elmer Ez301 spectrophotometer (Shelton, CT, USA). Total tannin content was determined
according to A.O.A.C. (1975). At the end of the experiment, fruit peel
color was measured by using Lovibond Tintometer GmbH.
Effect of Carbon Dioxide-Enriched Atmosphere…
7
Antioxidants and Phenolics Extraction Method
There are no satisfactory solvent extraction methods suitable for the
isolation of all classes of food antioxidants and phenolics or even for a
specific class of these components. This is due to the chemical nature of
food antioxidants and phenolics, which vary from being simple to being
very highly polymerized (Shahidi and Naczk, 2004). Therefore, the
extraction of antioxidant compounds and total phenolics for untreated
fruits was carried using five different solvents which have been used in
other studies (Ou, et al., 2001; Vinson, et al., 2001; Kalt, et al., 2001;
Huang, et al., 2002). The fruit sample was extracted using 40 ml of
water, phosphate buffer 75 mM, pH 7.4, ethanol (containing 0.1% formic
acid), or ethanol: water(1:1, v/v).
A 150 µl sample extract was introduced into a 3 ml fluorescence
cell, followed by 150 µl of 0.12 150 µM disodium FL solution, and 2055
ml 75 mM phosphate buffer was used as a blank. Trolox (a water-soluble
α tocophenol analogue) at 2.5, 5, and 10 µM was used as a standard. The
cell was incubated at 37°C for 15 min in a water bath. The initial
fluorescence (ƒ0) was measured at the excitation wavelength of 515 nm
using an RF-540 Shimadzu spectrofluorophotometer (Shimadzu, Kyoto,
Japan). After ƒ0 was recorded, 150 µl of 320 mM AAPH reagent, as a free
radical generator, was added into a cell and mixed well using a glass rod.
Fluorescence was measured and recorded every 5 min (ƒ5, ƒ10, ƒ15, …,
ƒ20) until the fluorescence of the last reading declined by >95 % from
the first reading (~60 min). The relative Oxygen Radical Absorbance
Capacity (ORAC) values were calculated according to the method of
Wang, et al. (1996). Values are expressed as micromoles of Trolox
equivalents (TE) per gram of fresh weight.
Measurements of Total Phenolics
Total phenolics were determined calorimetrically using FolinCiocalteau reagent as described by Velioglu, et al. (1998). Two hundred
milligrams of sample were extracted for 2 h with 2 ml of 50% methanol
at room temperature on an orbital shaker set at 200 rpm. The mixture was
centrifuged for 15 min, and the supernatant was decanted into 4 ml vials.
The supernatant was used for total phenolics assay. The extract (200 µl)
was mixed with 1.5 ml of Folin-Ciocalteau reagent (previously diluted
8
D.A. El-Rayes
10-fold with distilled water) and allowed to stand at room temperature for
5 min. A 1.5 ml sodium bicarbonate solution was added to the mixture.
After 90 min at 22°C, absorbance was measured at 725 nm using a UV1601 Shimadzu spectrophotometer. Total phenolics were quantified from
a calibration curve obtained by measuring the absorbance of known
concentrations of ferulic acid standard.
Extraction and Determination of Flavonoids
Powdered oven-dried Barhy date fruits (1g) were extracted in a
Soxhlet extractor with 100 ml ethanol for 1 hour and the extract filtered.
A known volume of extract was placed in a 10 ml volumetric flask.
Distilled water was added to make 5 ml, and 0.3 ml NaNO2 (1:20) were
added. Five minutes later, 0.3 ml AlCl3 (1:10) were added. After 6 min,
2 ml 1 mol litre−1 NaOH were added and the total was made up to 10 ml
with distilled water. The solution was mixed well again and the
absorbance was measured against a blank at 510 nm with a M8500 UVvisible spectrophotometer (Taizhou Radio Factory) (Zhuang, et al.,
1992).
Measurement of Total Carotenoids
Total carotenoids were extracted according to the method of
Talcott and Howard (1999). Two grams of the sample were extracted
using 25 ml acetone/ethanol (1:1, v/v) with 200 mg/l butyl hydroxyl
toluene (BHT). Samples were centrifuged at 1500 g for 15 min. The
supernatant was brought to 100 ml with the extraction solvent, and
absorbance at 470 nm was measured using a UV-1601 Shimadzu
spectrophotometer. Total Carotenoids were calculated according to the
method of Gross (1991).
Statistical Analysis
Data were analyzed using a factorial design with five replicates per
treatment, using the Student-Newman-Keul’s Test. The least significant
differences were used to compare means at P ≤ 0.05 according to the
procedure outlined by Snedecor and Cochran (1980). The experiment was
carried out for two successive seasons.
Effect of Carbon Dioxide-Enriched Atmosphere…
9
Results and Discussion
Storage Period
A great deal of extension had occurred in the storage period of full
mature ‘Barhy’ date fruits stored at 0ºC under modified atmosphere
conditions (Fig. 1). Data revealed that modified atmosphere and cold
storage treatments retarded effectively ripening and senescence of ‘Barhy’
full mature dates. All CO2 enriched treatments significantly improved the
storage ability of the fruits. Evidently, elevating CO2 concentration inside
the storing containers to 20% at 0ºC resulted in extending the storage
period of the date fruits 2.8 times than those stored at the same temperature
(0ºC) under common atmosphere conditions. ‘Barhy’ fruits stored at 0ºC
under common atmosphere conditions were discarded totally after two
months. On the contrary, fruits stored under modified atmosphere
containing 20% CO2 at 0ºC maintained their quality and showed longer
storage ability achieving 173 days.
Fig. 1. Effect of different storage temperatures and CO2 concentrations on storage ability of
Barhy date fruits.
Each value in the figure is a mean of five replicates, and three measurements were conducted for each
replicate. Means followed by the same letter, within a curve line are not significantly different (p ≥ 0.05). The
least significant differences at P ≤ 0.05 were: Storage temperature: 8.213, carbon dioxide concentration:
12.571, and the interaction: 13.875.
10
D.A. El-Rayes
Longest storage period occurred when date fruits were stored at 0ºC
under MA containing 20% CO2, followed by those containing 10% and
5% CO2, respectively. On the contrary, shortest storage period was
observed in fruits stored at 6ºC under common air atmosphere. A clear
relationship was observed between CO2 concentration inside the storing
containers and the storage ability of the fruits. The higher the CO2
concentration, the longer the storage period.
Elevated carbon dioxide during storage delays fruit ripening and
reduces respiration rate of the fruits, which extends storage life and
maintains quality. The use of elevated CO2 at storage atmosphere for
preserving fruit quality, reducing respiration rate of the fruits, and
delaying fruit deterioration has been described (Al-Redhaiman, 2005;
Attia, et al.,1997; El-Rayes and Ahmed, 2001; and Kader, 2002).
Soluble Solid Content
Percentage of soluble solid contents
The percentage of soluble solids content in Barhy date fruits was not
affected significantly by CO2 or cold storage treatments (Fig. 2).
35
30
0.03% carbon dioxide
25
5 % carbon dioxide
20
10 % carbon dioxide
15
20 % carbon dioxide
10
0
2
4
6
Storage temperature ( º C)
Fig. 2. Percentage of soluble solid contents in Barhy date fruits stored at different storage
temperatures under different carbon dioxide concentrations.
The least significant differences at P ≤ 0.05 were: Storage temperature 0.387, carbon dioxide concentration
0.422, and the Interaction 0.498.
Perhaps because ripening processes after "Bisr" stage of fruit
development have only a slightly effect on SSC%. A slight increase in
SSC% occurred in most treatments under investigation. This increase
could be due to the conversion of some insoluble compounds into soluble
compounds (such as the conversion of protopectin into pectin), or as
11
Effect of Carbon Dioxide-Enriched Atmosphere…
a result of the water loss from the fruits. Lower moisture contents could
affect SSC% positively as shown by Thompson and Abboodi (2003).
Total Tannin Contents
Both modified atmosphere conditions and cold storage temperature
affected tannin content in Barhy date fruits during storage (Fig. 3). Fruit
total tannin contents showed an inversely proportional values to the
storage period. At the end of the experiment, lowest fruit tannin content
values were observed in fruits stored at 6ºC under common atmosphere
conditions. Data indicated that fruit total tannin contents were closely
associated with fruit ripening process during the storage period, the more
advanced stage of ripening, the lower the fruit tannin content.
5
Total tannin contents
(µ mol.g.-1)
4.5
4
3.5
3
2.5
2
0.03% CO2
1.5
5% CO2
1
10% CO2
0.5
20% CO2
0
0
2
4
6
Storage temperature (°C)
Fig. 3. Total tannins contents (μ mol.g–1) in Barhy date fruits stored at different storage
temperatures under different carbon dioxide concentrations.
The least significant differences at P ≤ 0.05 were: for storage temperature 0.251, for carbon dioxide
concentration 0.232, and for the interaction 0.311.
Tannin contents of date fruits were at maximum concentration in the
Khalal (Bisr) stage (full mature stage of development) and gradually
decreased to reach a minimum concentration in the ripe stage (Rutab)
(Sawaya and Mashadi, 1983). At the beginning of the experiment, Barhy’
date fruits in the Khalal stage contained 4.2% tannins on dry weight basis
(Fig. 3). However, at the end of the experiment total tannins in fruits
stored at 6ºC under common atmosphere conditions decreased
significantly recording only 2.8%. No significant changes in tannin
content occurred in MA treated fruits supplied with 20% CO2 and stored
12
D.A. El-Rayes
at 0ºC. Moreover, fruit tannin contents showed directly proportional
values to CO2 concentration and cold storage temperature. Fruits stored at
MA and supplied with 20% CO2 at 0ºC contained the highest fruit tannin
contents compared to all other treatments and maintained, after 173 days
of storage, almost the same tannin values as it was at the beginning of the
experiment. This clearly indicates the positive effect of CO2 and cold
temperature treatments in retarding the fruit ripening process and
subsequently maintaining tannin contents. These findings are in harmony
with those of Rouhani and Bassiri, 1976 and Sawaya & Mashadi, 1983.
Total Sugar Contents
Neither modified atmosphere conditions nor cold storage temperature
treatments had any significant effect on total sugar contents of ‘Barhy’
date fruits. At the beginning of the experiment, total sugar content was
75.29% on a dry weight basis (Table 1). Evidently, at the end of the
storage period, a slight increase was observed in fruit total sugar content.
This increment occurred in all treatments under study but with different
rates. Highest rate of total sugar increment during storage period
occurred in fruits stored under common air atmosphere at 6ºC. On the
contrary, lowest rate of total sugar increment was observed in fruits
stored under MA with 20% CO2 at 0ºC. A clear relationship was
observed between fruit stage of development and total sugar content. The
more advanced stage of fruit development and ripening, the higher the
sugar content. In general, there was a slight increase in fruit total sugar
content as the fruits passed from the Khalal to Rutab (full ripen fruits)
stage. These findings are similar to those reported earlier by other
workers on various date cultivars (Coggins and Knapp, 1969; and
Sawaya & Mashadi, 1983).
Fruit Peel Color Analysis
Fruit peel color analysis indicated that both modified atmosphere
conditions and cold storage treatments influenced significantly fruit peel
lightness (L* values), the locus relative to purplish-red-bluish-green (a*
values), the locus relative to yellow-blue (b* values), the index analogous
to color intensity (c* values), and hue angle (h* values) (Tables 2-6 and
Fig. 4&5). A clear relationship was observed between CO2 concentration
inside the storing containers and the fruit peel color analysis parameters.
13
Effect of Carbon Dioxide-Enriched Atmosphere…
Fruit peel L*, a*, b*, c*, and h* values showed directly proportional
values to CO2 concentration and cold storage temperature.
Table 1. Changes in the percentage of total sugar contents in Barhy date fruits stored at
different storage temperatures under different carbon dioxide concentrations.
Storage
temperature
(°C )
Total sugar
contents at
zero time
Carbon dioxide concentration
Average
0.03%
5.0%
10.0%
20.0%
75.6
74.9
74.8
74.3
74.9a
77.4
77.7
75.8
75.2
76.5a
4ºC
78.2
77.8
76.7
76.1
77.2a
6ºC
79.6
78.4
78.7
77.8
78.6a
Average
77.7a
77.2a
76.5a
75.9a
0ºC
2ºC
74.1
Each value in the table is the mean of five replicates, and three measurements were conducted for each
replicate. Means followed by the same letter, within a column are not significantly different (p ≥ 0.05) and
means followed by the same letter, within a row are not significantly different (p ≥ 0.05). LSD at 0.05 for the
interaction: NS.
Table 2. Effect of storage temperature and carbon dioxide concentrations on L* values
(lightness) of Barhy date fruit peel color. At the beginning of the experiment, fruits
were at Khalal stage, but they varied at the evaluation time between Khalal and
Rutab stages.
Storage
temperature
(C )
Fruit color
at
zero time
Carbon dioxide concentration
Average
0.03%
5.0%
10.0%
20.0%
0ºC
37.7
40.7
41.5
65.7
46.4a
2ºC
32.7
35.1
34.1
63.8
41.4b
31.3
33.5
33.8
43.5
35.5c
6ºC
29.4
31.6
33.1
36.4
32.6c
Average
32.8c
35.2b
35.6b
52.4a
4ºC
67.1
Each value in the table is the mean of five replicates, and three measurements were conducted for each
replicate. Means followed by the same letter, within a column are not significantly different (p ≥ 0.05) and
means followed by the same letter, within a row are not significantly different (p ≥ 0.05). LSD at 0.05 for the
interaction: 4.261.
14
D.A. El-Rayes
Fruits stored at MA and supplied with 20% CO2 at 0°C showed the
nearest values to yellow color b* compared to all other treatments. In
Barhy date fruits, decrease of fruit peel L* values in peel color is
associated with fruit ripening processes. Subsequently, the effect of both
MA conditions (at 20% CO2) and cold storage (at 0°C) on retarding the
ripening process resulted in maintaining the fruit peel lightness (L*) and
yellow color (b*) the closest to the fruit peel color at time zero.
Table 3. Effect of storage temperature and carbon dioxide concentrations on a* values (the
locus relative to purplish-red-bluish-green) of Barhy date fruit peel color.
Storage
temperature
(ºC )
Fruit color
at
zero time
Carbon dioxide concentration
Average
0.03%
5.0%
10.0%
20.0%
0°C
2.1
3.6
4.1
4.5
3.6a
2ºC
1.8
2.9
3.0
4.3
3.0b
1.5
2.1
2.4
2.3
2.1c
6ºC
1.3
1.4
1.8
1.8
1.6d
Average
1.7d
2.5b
2.1c
3.2a
4ºC
4.7
Each value in the table is the mean of five replicates, and three measurements were conducted for each
replicate. Means followed by the same letter, within a column are not significantly different (p ≥ 0.05) and
means followed by the same letter, within a row are not significantly different (p ≥ 0.05). LSD at 0.05 (p ≥
0.05) for the interaction: 0.461.
Table 4. Effect of storage temperature and carbon dioxide concentrations on b* values (the
locus relative to yellow-blue) of Barhy date fruit peel color.
Storage
temperature
(ºC )
Fruit color
at
zero time
Carbon dioxide concentration
Average
0.03%
5.0%
10.0%
20.0%
0ºC
16.9
18.9
22.8
27.2
21.5a
2ºC
13.2
16..2
27.5
18.8b
4ºC
28.2
15.5
8.4
12.7
15.7
18.0
13.7c
6ºC
5.1
7.3
9.5
12.8
8.7d
Average
10.9d
13.6c
16.0b
21.3a
Each value in the table is the mean of five replicates, and three measurements were conducted for each
replicate. Means followed by the same letter, within a column are not significantly different (p ≥ 0.05) and
means followed by the same letter, within a row are not significantly different (p ≥ 0.05). LSD at 0.05 for the
interaction: 2.151.
15
Effect of Carbon Dioxide-Enriched Atmosphere…
Table 5. Effect of storage temperature and carbon dioxide concentrations on C* values (an
index analogous to color intensity) of Barhy date fruit peel color.
Storage
temperature
(ºC )
0ºC
2ºC
4ºC
6ºC
Average
Fruit color
at
zero time
27.2
Carbon dioxide concentration
0.03%
5.0%
10.0%
20.0%
18.2
16.6
4.5
2.3
10.4c
22.5
26.6
6.5
2.7
14.6b
23.2
21.6
7.2
3.5
13.9b
26.6
25.6
21.6
5.8
19.9a
Average
22.6a
22.6a
10.0b
3.6c
Each value in the table is the mean of five replicates, and three measurements were conducted for each
replicate. Means followed by the same letter, within a column are not significantly different (p ≥ 0.05) and
means followed by the same letter, within a row are not significantly different (p ≥ 0.05). LSD at 0.05 for the
interaction: 2.475.
Table 6. Effect of storage temperature and carbon dioxide concentrations on h* values (hue
angle1) of Barhy date fruit peel color.
Storage
temperature
(ºC )
0ºC
2ºC
4ºC
6ºC
Average
Fruit color
at
zero time
80.5
Carbon dioxide concentration
Average
0.03%
5.0%
10.0%
20.0%
79.9
31.3
26.9
24.9
40.8c
79.9
52.7
27.9
26.5
46.8b
79.5
61.2
33.8
30.7
51.3ab
78.5
59.6
49.5
38.4
56.5a
79.5a
51.2b
34.5c
30.1c
Each value in the table is the mean of five replicates, and three measurements were conducted for each
replicate. Means followed by the same letter, within a column are not significantly different (p ≥ 0.05) and
means followed by the same letter, within a row are not significantly different (p ≥ 0.05). LSD at 0.05 for the
interaction: 7.562
1
hue angle is the angle between the hypotenuse and 0º on the a* (the locus relative to purplish-red-bluishgreen) axis.
Fig. 4. Storing Barhy date fruits at full mature stage (Bisr) under high CO2 concentrations
(higher than 30% CO2) could result in CO2 injury as shown above (data are not
reported).
16
D.A. El-Rayes
Fig. 5. The color change during the different stages of Barhy fruit development.
Antioxidants and Phenolics Extraction Method
Data in Table 7 compares the effect of extraction methods on
antioxidant activity and content of total phenolics in Barhy date fruits
using four different solvents. Significant (p ≤ 0.05) differences existed
among different solvent used. Extraction into phosphate buffer (75 mM,
pH 7.4) gave the highest antioxidant activity (7986 µmol of TE/g),
whereas ethanol afforded the (5832 µmol of TE/g) among the solvents
used. These results suggest that most of the antioxidants in date fruits are
water soluble (hydrophilic). In contrast to antioxidant activity, ethanol/
water (50: 50, v/v) yielded the highest recovery of total phenolics (284
mg of FAE/100g). This could be due to the solubility differences of
phenolic acid in ethanol, water, or their mixture. Thus, phosphate buffer
for antioxidant activity and ethanol/ water (50: 50, v/v) for total
phenolics was selected to extract the remaining treatments.
Table 7. Comparison of extraction solvents for the contents of antioxidant activity (µ mol of
a
TE/g fresh) and total phenolics in Barhy date fruit .
a
c
Antioxidant activityb
(µ mol of TE/g)
Total phenolics
(mg of FAE/100g)
Water
7338 + 628e
226 + 7 g
Phosphate buffer (75 mM, pH 7.4)
7986 + 614d
232 + 8 f
Ethanol :Water(1:1)
6678 + 523f
284 + 11d
Ethanol
5832 + 533g
251 + 9 e
Extraction solvent
Data are expressed as mean + SD on fresh weight basis. Each value in the table is the mean of five replicates,
and three measurements were conducted for each replicate. Means + SD followed by the same letter, within a
column are not significantly different (p ≥ 0.05) .
b
Antioxidant activity expressed as micromoles of Trolox equivalents (TE) per gram fresh weight.
c
Total phenolics are expressed as milligrams of ferulic acid equivalents (mg of FAE/100g).
17
Effect of Carbon Dioxide-Enriched Atmosphere…
Total Phenolics
Significant differences (p ≤ 0.05) in total phenolic values were
observed among Barhy date fruits stored under different modified
atmosphere and cold storage treatments (Table 8).
Table 8. Contents of total phenolics (mg.100 g–1 dry weight) in Barhy date fruits as affected
a
by storage temperature and carbon dioxide concentrations .
Storage
temperature
(ºC )
Carbon dioxide concentration
Average
0.03%
5.0%
10.0%
20.0%
0ºC
18.7
19.4
19.5
20.8
19.6 a
2ºC
18.4
18.8
19.1
20.5
19.2 a
14.7
16.8
17.5
19.4
17.1 b
14.4 c
4ºC
a
Total
b
phenolics
at zero time
21.62
6ºC
12.9
13.9
14.0
16.8
Average
16.2 b
17.2b
17.5b
19.4 a
Each value in the table is the mean of five replicates, and three measurements were conducted for each
replicate. Means followed by the same letter, within a column or a row are not significantly different (p ≥
0.05).
b
Total phenolics expressed as micromoles of ferulic acid equivalents (FAE) per 100 grams of fresh weight.
The higher total phenolic values were observed in fruits at the
beginning of the experiment (at zero time before any storage treatment).
However, at the end of the experiment, no significant differences (p ≤ 0.05)
were observed between fruits stored at 0ºC under 20.0% CO2 for 173 days
and fruits at zero time regarding total phenolic values. Carbon dioxide
treatment at 20.0% maintained fruit contents of total phenolic values
significantly higher than all other CO2 treatments. Moreover, low storage
temperature (0ºC and 2ºC) maintained fruit contents of total phenolic
values significantly higher than all other cold storage treatments used in
this study. During the fruit development, the conversion of Barhy date
fruits from full mature stage to ripening stage caused a significant loss in
total phenolics (Table 8). This loss could be due to the decomposition of
natural phenolics in dates during ripening processes. The reduction in total
phenolic values during the conversion from full mature stage to ripening
stage of development has also been reported for other fruits.
Larrauri, et al., 1997, reported decreases in the total phenolic values
of red grape at high temperature during and after ripening processes.
18
D.A. El-Rayes
Contents of Flavonoids and Caroteinoids
Barhy date fruits contents of both flavonoids and caroteinoids did
not show any significant difference among different treatments stored
under different modified atmosphere and cold storage conditions (Table
9). Although a slight increase was observed in both flavonoids and
caroteinoids contents in Barhy date fruits during the storage period
compared with their values at zero time (fruits were at full mature stage
of development), however, this increment did not reach the level of
significance between the different treatments.
Table 9. Contents of total flavonoids (mg.100 g–1 dry weight) and total carotenoids (mg.100
g–1 dry weight) in Barhy date fruit as affected by storage temperature and carbon
dioxide concentrations.
Storage
temperature
Total
flavonoids
at zero time
Carbon dioxide concentration
Average
0.03%
5.0%
10.0%
20.0%
2.51
2.45
2.45
2.43
2.46a
2.58
2.56
2.52
2.49
2.54a
2.61
2.61
2.59
2.51
2.58a
6ºC
2.64
2.62
2.61
2.55
2.62a
Average
2.59a
2.56a
2.55a
2.50a
5.83
5.79
5.72
5.67
5.75a
6.08
5.74
5.71
5.63
5.79a
6.15
6.04
6.11
5.81
6.03a
6ºC
6.21
6.15
6.19
6.18
6.18a
Average
6.07a
5.93a
5.94a
5.82a
Total flavonoids (mg.100 g–1 dry weight)
0ºC
2ºC
4ºC
2.38
Total carotenoids (mg.100 g–1 dry weight)
0ºC
2ºC
4ºC
5.58
Each value in the table is the mean of five replicates, and three measurements were conducted for each
replicate. Means followed by the same letter, within a column of each character are not significantly different
(p ≥ 0.05) and means followed by the same letter, within a row of each character are not significantly different
(p ≥ 0.05). LSD at 0.05 for the interaction: NS.
The lowest values of fruit contents of both flavonoids and
caroteinoids were observed in fruits at the beginning of the experiment
(at zero time before any storage treatment). In contrast, the highest values
of fruit contents of both flavonoids and caroteinoids were observed in
fruits stored at 6ºC in ambient air composition (0.03% CO2). This
increment in the values of fruit contents of both flavonoids and
Effect of Carbon Dioxide-Enriched Atmosphere…
19
caroteinoids was proportionally associated with the ripening processes
occurring in the fruits. The closer the fruit to the full ripe stage the higher
the content of both flavonoids and caroteinoids .Subsequently, the effect
of both MA conditions (at 20% CO2) and cold storage (at 0ºC) on
retarding the ripening process resulted in maintaining the fruit contents of
both flavonoids and caroteinoids closest to their values at time zero.
Conclusion
Modified atmosphere conditions maintained fruit skin color, and
overall quality parameters of date fruits. Fruits stored under MA with
high CO2 concentrations (20% CO2) looked exactly as the freshly
harvested fruits. A positive proportional relationship between CO2
concentration and both fruit quality and storage ability was recorded. The
effect of both MA conditions (at 20% CO2) and cold storage (at 0ºC) on
retarding the ripening process resulted in maintaining the fruit contents of
total phenolic, flavonoids, and caroteinoids values closest to their values
at time zero. Fruits stored under low temperature conditions (0°C) or
relatively high CO2 concentration (20% CO2) did not show any chilling
or CO2 injury symptoms. In this respect, a modified atmosphere system
could be developed for ‘Barhy’ full mature date fruits that can effectively
retard ripening and senescence, and allow shipping of the fruit to distant
markets with acceptable quality.
References
Al-Redhaiman, K.N. (2005) "Chemical changes during storage of ´Barhy` dates under
ccontrolled atmosphere conditions", Hort. Science, 40(5): 1413-1415.
AOAC (1975) Official Methods of Analysis. Association of Official Analytical Chemists.,
Washington DC, 12th ed, pp: 564-596.
Attia, M.M., Etman, A.A., Hussein, A.M. and El-Naggar, N. (1997) Effect of wrapping with
two polyethylene types on postharvest behavior and shelf life of three soft date cvs,
Zagazig J. Agric. Res., 24: 124-134.
Carlos, H.C., Garner, D. and Crisosto, G. (2002) Carbon dioxide-enriched atmospheres during
cold storage limit losses from Botrytis but accelerate rachis browning of 'Red Globe' table
grapes, Postharvest Biology and Technology, 26: 181-189.
Coggins, C.W. and Knapp, J.C.F. (1969) Growth, development and softening of Deglet Noor
date fruits, Date Growers’ Inst. Report, 46: 11-14.
Dubios, M., Gilles, K.A., Hamilton, J.K., Rebers, P.A. and Smith, F. (1956) Colorimetric
method for determination of sugars and related substances, Anal. Chem., 28: 350-356.
El-Rayes, D.A. and Ahmed, D.M. (2001) Effect of modified atmosphere packaging and cold
storage on storage period and quality of “Tommy Atkins” mango fruits, Assiut J. Agric.
Sci., 32:251-262.
20
D.A. El-Rayes
Frankel, E. (1995) Nutritional Benefits of Flavonoids, International Conference on Food
Factors: Chemistry and Cancer Prevention, Hamamatsu, Japan, Abstracts, C6-2.
Gross, J. (1991) Pigments in Vegetables: Chlorophylls and Carotenoids, Van Nostrand Reinhold,
New York.
Hassan, I.M. and El-Sheemy, M.G. (1989) Freeze thaw biochemical changes in three Egyptian
date varieties, Annals Agric. Sci. Cairo, 34:205-222.
Hegazy, M.K., Fahmy, M.A., Sobaih, M.A. and Abdul-Samad, M.A. (2003) Effect of Some
Postharvest Treatments on Zagloul Date Fruits During Storage, Proceedings of the
International Conference on Date Palm, King Saud Univ., Qassim, Kingdom of Saudi
Arabia, pp: 353-362.
Huang, D., Ou, B., Hampsch-Woodill, M., Flanagan, J.A. and Deemer, E.K. (2002)
Development and validation of oxygen radical absorbance capacity assay for lipophilic
antioxidants using randomly methylated B-cyclodextrin as the solubility enhancer, J. Agric.
Food Chem., 50: 1815 – 1821.
Kader, A.A. (2002) Postharvest Biology and Technology: An Overview, pp. 39-47. In: A.A.
Kader (ed.), Postharvest Technology of Horticultural Crops, 3rd ed., Univ. of Calif., Davis,
Agriculture and Natural Resources, Publication 3311.
Kalt, W., Ryan, D.A.J., Duy, J.C., Prior, R.L., Ehlenfeldt, M.K. and Vander Kloet, S.P.
(2001) Interspecific variation in anthocyanins, phenolics, and antioxidant capacity among
genotypes of highbush and lowbush blueberries (Vaccinium Section cyanococcus spp.), J.
Agric. Food Chem. 49: 4761 – 4767.
Larrauri, J.A., Rupérez, P. and Saura-Calixto, F. (1997) Effect of drying temperature on the
stability of polyphenols and antioxidant activity of red grape pomace peels, J. Agric. Food
Chem., 45 (4): 1390 – 1393.
Larson, R.A. (1988) The antioxidants of higher plants, Phytochemistry, 27: 969–978.
Navarro, S., Donahaye, E., Rindner, M., Azrieli, A., Aksoy, U., Fergusson, L. and Hepaksoy,
S. (1998) Storage of dried fruits under controlled atmospheres for quality preservation and
control of nitidulid beetles, Acta Hortic., 480: 221-226.
Ou, B., Hampsch-Woodill, M. and Prior, R.L. (2001) Development and validation of an
improved oxygen radical absorbance capacity assay using fluorescein as the fluorescent
probe, J. Agric. Food Chem., 49: 4619 – 4626.
Rouhani, I. and Bassiri, A. (1976) Changes in physical and chemical characteristics of Shaahni
dates during development and maturity, J. Hort. Sci., 51:489-494.
Sawaya, W.M. and Mashadi, A.S. (1983) Sugars, Tannins, and Vitamin Contents of Twenty-five
Date Cultivars Grown in Saudi Arabia, Proceedings of Date Palm Symp. King Faisal Univ.,
pp: 468-479.
Snedecor, G.W. and Cochran, W.G. (1980) Statistical Methods, 7th ed. Iowa State Univ. Press,
Ames, Iowa, USA.
Talcott, S.T. and Howard, L.R. (1999) Phenolic autoxidation is responsible for color
degradation in processed carrot puree, J. Agric. Food Chem., 47: 2109 - 2115.
Thompson, K.A. and Abboodi, A.H. (2003) Modified Atmosphere Packaging, Proceedings of
the International Conference on Date Palm. King Saud Univ., Qassim, Kingdom of Saudi
Arabia, pp: 363-394.
Velioglu, Y. S., Mazza, G., Gao, L. and Oomah, B.D. (1998) Antioxidant activity and total
phenolics in selected fruits, vegetables, and grain products, J. Agric. Food Chem., 46: 4113
– 4117.
Vinson, J.A., Su, X., Zubik, L. and Bose, P. (2001) Phenol antioxidant quantity and quality in
foods: Fruits, J. Agric. Food Chem., 49: 5315 – 5321.
Wang, H. G. Cao and Prior, R.L. (1996) Total antioxidant capacity of fruits, J. Agric. Food
Chem., 44: 701-705.
Zhuang, X.P., Lu, Y.Y. and Yang, G.S. (1992) Extraction and determination of flavonoid in
ginkgo, Chinese Herbal Medicine, 23: 122–124.
Effect of Carbon Dioxide-Enriched Atmosphere…
21
#$ %$& !" ' (&
– – ! "" .
+ % &
'
*
(!#$) .
!#$ ,0 1
/,& -&. '
*'$ % . 3448/3447. 3447/3445
'+ /(º 8 /5 /3 /:) :$
; ?34 . / >4, 7 /4,4=) *.+ + '< *
:$
'+ C
* AB @. 0. .(*.+ + '<
E E /*'$ ; D $
*.+ + '<
*. /.:
*+. /
;. !BF . *
'< ?34 '+ /º : ; '$
!@ & % /
;. !@ GH *.+ +
+ .I$J #
1
!+ 0
/'$ ;0
. /*.
+ 'M 1
K L * AB @.
N.@. ' E /'$ GE. /
;. *.+
*+
% ,@:$
; '$
: H
C
P . >O3 ;
*'$
/*.+ + '< ?34 '+ G ;.
22
D.A. El-Rayes
.
*
I.
M . / º : ;
GH .P.1
PM . /+ . /B
. /;. @J Q , / #
1
C
.*.+ + '< *
1:
'+ $ @