Modified Atmosphere Packaging of Date Fruit (Phoenix dactylifera L.

)
Cultivar ‘Barhee’ in Khalal Stage
S.M.H. Mortazavi K. Arzani and A.A. Arujalian
College of Agriculture College of Agriculture
Department of Horticultural Science Department of Horticultural Science
Shahid Chamran University Tarbiat Modarres University
Ahvaz Tehran
Iran Iran

Keywords: date palm (Phoenix dactylifera L.), modified atmospheres packaging, quality
attributes, storage, ‘Barhee’

Abstract
Considering the date fruit (Phoenix dactylifera L.) ‘Barhee’ is mainly
harvested at the khalal stage, the quality changes of fresh fruits were studied under
modified atmosphere packaging (MAP). Fruit was packed in barrier bags and
exposed to the ambient air (passive MAP) and different concentrations of CO2 (5, 15
and 30%) within the packaging (active MAP) by using microperforated films as
control. Fruits were stored at 4°C and physiochemical changes were studied at
7 days intervals during 28 days of storage. Modified atmosphere containing 30%
CO2 caused almost half of the fruits to turn into low quality rutab, while the best
quality and longest shelf-life of khalal fruits was gained with 5% CO2 concentration.
Also, passive MAP compared with control samples, showed acceptable results by
extending the shelf-life of khalal date fruits.

INTRODUCTION
Date (Phoenix dactylifera L.) is a berry fruit whose development divides into five
stages namely hababook, kimri, khalal, rutab and tamar. At the khalal stage, fruits are
physiologically mature, hard and crisp with over 50% moisture content, bright yellow or
red in color and very perishable. In general, fruits at khalal stage are ready for commercial
trade as “fresh” fruit but this applies only to those cultivars which are sweet, with a low
amount of tannin and low astringency (Barreveld, 1993). Some date cultivars are suitable
for marketing at the khalal stage including ‘Barhee’, ‘Bereim’, ‘Hayany’ and ‘Khalas’
among them ‘Barhee’ is the most popular cultivar worldwide (Mortazavi et al., 2007).
The khalal fruits that are usually harvested at the end of July are highly perishable and
must be transported to the market as soon as possible (Glasner, 2002). Any delay in
transport or improper storage conditions result in quick appearing of rutab spots and
surface wrinkling accompanied by a loss of flavor and taste (Mortazavi et al., 2007). The
strategy for exporting khalal dates would make it necessary to develop new methods to
delay fruit ripening during handling and storage. Modified atmosphere packaging (MAP)
is now being used for extending the shelf-life and reducing the waste of a wide range of
fruits and vegetables. There are few studies about use of vacuum and modified
atmosphere packaging for date fruits at the khalal stage. Al-Redhaiman (2004) stored full
mature ‘Barhee’ date fruits under three CO2 concentrations (5, 10 or 20%) at 0°C and
reported that fruits under 20% CO2 have a statically longer storage period, lasting for
26 weeks. Also, Achour et al. (2003) determined that dehydrating of ‘Deglet Nour’ dates
at tamar stage decreased at MA condition with 20% CO2 and 80% N2 during the storage
period. A previous study by authors has demonstrated the potential interest of using
passive MAP to reduce the weight loss and appearance of low quality rutab spots of
‘Barhee’ date picked at khalal stage. However, in the vacuum packaging, a large part of
fruits turned to low quality rutab and fruit firmness reduced considerably (Mortazavi et al.,
2007). The objective of this work was to study the influence of some active and passive
MAP conditions accompanied by fruit to stalk junction status on the physiological
properties, quality attributes and storability of ‘Barhee’ date fruits at the khalal stage.

Proc. 4th Int. Date Palm Conference 1063

Eds.: A. Zaid and G.A. Alhadrami
Acta Hort. 882, ISHS 2010
MATERIALS AND METHODS
‘Barhee’ date fruits were harvested at khalal stage from a commercial orchard in
Ahvaz, Khuzestan province, Iran according to yellow skin color and about 30% soluble
solids concentration. The fruit were precooled immediately and transported to the
laboratory. They were selected for no visual defects and basis of uniform size, color and
without rutab spots, then washed with sodium hypochlorite solution 0.5% for 2 min,
rinsed with tap water and dried prior to packaging.
Fruits were divided into eight lots each of 60 fruit, then each lot was divided into
three replicates of 20 (200±5 g). Each set of three replicates was put into a dish tray and
placed in a barrier nylon/polyethylene plastic bag (25×35 cm) given one of the eight
treatments: (5%-J) joint fruits+5% O2: 5% CO2; (5%-D) detached fruits+5% O2: 5% CO2;
(15%-J) joint fruits+5% O2: 15% CO2; (15%-D) detached fruits+5% O2: 15% CO2; (30%-
J) joint fruits+5% O2: 30% CO2; (30%-D) detached fruits+5% O2: 30% CO2; (PM)
detached fruits in passive MAP; and (C) control (detached fruits, perforated film
providing ambient air atmosphere within the packages). All active MAP treatments (T1 to
T6) were performed by creating a vacuum in a Henkelman vacuum pack instrument
(200A) followed by flushing the gas mixture 1 bar pressure before heat sealing and N2
used as a balance gas. All samples were stored at 4°C for up to 28 days. The experiment
was conducted based on a completely randomized design (CRD). The data were analyzed
with MSTAT-C (version 1.42) statistical package, and means compared by Duncan’s
Multiple Range Test (DMRT) at 0.01 and 0.05 probability levels. Visual examinations
and other quality attributes were evaluated initially and periodically at seven day intervals.
The gas atmosphere in the head space of the bags was analyzed using an O2/CO2 gas
analyzer. The fruit subjected to all treatments were weighed before and after storage and
data were expressed as percentage of weight loss. Fruit firmness was measured by a
Wagner Penetrometer (FT 011). Titratable acidity was calculated as percentage of malic
acid by titrating 10 g/100 ml of the date extract with a solution of NaOH (0.01 N) till pH
8.1. The pH was measured by a Metrohm pH meter. The level of sugars was measured
as °Brix by an Atago refractometer. Water activity (aw) values of fruits were measured at
30°C with a hygrometer. To determine the wrinkled area or rutab spots, to have more
accuracy of data, an image processing procedure was used (Rocculi et al., 2005). Images
were obtained, using a color plane scanner (true color-24 bit, resolution of 600×600 dpi),
and by positioning the fruit halves on a scanner held on a black box, to exclude the
surrounding light. The saved images were opened by a program that had been written by
authors in Matlab® software to calculate the percentage of selected area fraction of fruit
and averaged data were considered as RSA or WAP for each unit.
RESULTS AND DISCUSSION
During the storage period of 28 days, the fruit respiration resulted in a
modification of the internal atmospheres and as expected, all treatments showed a reduced
O2 and an increased CO2 level (Fig. 1). The oxygen concentration decreased sharply in
the first seven days, from 5 to less than 2.7% and continued with a little decreasing
amplitude in the following days. The final O2 concentration was less than 0.07% for all
treatments after 28 days storage. However the CO2 production rate was higher at the first
week for pouches containing 5% CO2 (5%-J and 5%-D) but the final concentration of
CO2 was in keeping with its concentration at the start of the experiment. Clear correlation
was observed between final and initial concentration of CO2 and its concentration reached
to about 60% for pouches containing 30% at the start of experiment. According to the O2
curves, differences between passive and active MAP were seen during the transient period,
then, drawing near and steady state was obtained after approximately 14 days of storage.
These were in agreement with the results of Charles et al. (2008) for fresh endives.
It was evident from this study that the rutab spots area (RSA) that appeared during
storage was correlated significantly with CO2 concentration within pouches. The higher
CO2 concentration promoted RSA and image processing of fruit surfaces in 30%-J and
30%-D treatments (30% CO2) showed 92.3 and 82.5% RSA respectively at the end of 28

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days storage. Fruits in pouches filled with 15% CO2, showed 49.5 and 58.8% rutab spots
for 15%-J and 15%-D respectively and samples in 5% CO2 condition (5%-J and 5%-D)
undergoing a smaller turning to rutab spots. Also when the storage period prolonged,
greater part of fruits changed to rutab in all treatments, particularly in fruits detached from
stalk (5%-D, 15%-D and 30%-D). Fruits in the perforated bags exposed to the air (C),
exerted highest WAP (24.25%) after 28 days of storage. WAP was negligible for other
treatments and the lowest value was recorded in fruits that received 30% CO2 (30%-J and
30%-D) at which a large part of fruits turned to rutab. Fruit to stalk junction had no major
effectiveness on the wrinkled area percentage. Appearing rutab spots and wrinkled
surface are the two main disorders restricting marketing, storage and exports of khalal
dates after harvest (Fig. 2a,b). However, turning fruit surface color to brown considered
as rutab spot, comparing obtained rutab fruits in this study, with those ripened naturally
on the tree, showed some major differences. Rutab spots in the fruits coming out of
storage can be described as CO2 injury similar to that reported by Serrano et al. (2005),
for sweet cherry at high CO2 concentrations. Elevated CO2 can prove to be fruit damage,
often inducing fermentation, particularly when fruit is sealed in packaging film of
insufficient permeability (Betts, 1996).
Regardless of gas composition within the package, fruit weight loss ranged
between 1.13-1.82 g/100 g under MAP conditions, while control fruits in perforated bags
(C) lost 10.48 g/100 g. The data revealed the pattern of reduction in fruit weight in all
MAP packages was almost the same after 7, 14, 21 and 28 days of storage and packaging
was effective in limiting weight loss of fruits (Table 1). As expected, the wrinkled area
percentage (WAP) followed by a similar pattern with fruit weight loss (Weight loss =
0.525 WAP + 0.499). Weight loss is a physiological event caused by loss of water from
the fruit surface to the surrounding atmosphere and loss of carbon on formation of CO2
during respiration (Rizzo and Muratore, 2009). It can be controlled by temperature,
humidity, and using proper packaging. In this work, for using barrier films, and minimum
package condensation observed, it can be assumed that a gentle increase in weight loss of
all treatments (except control), is caused mainly by the biochemical reactions of fruit cell
components.
The initial firmness measured at the start of experiment was 3.4 kg. The following
decrease in firmness during 28 days cold storage to 0.66 kg (average of all treatments)
showed a clear response to the different MA conditions applied (Fig. 2c,d). Prolonging
the storage duration, decreased the firmness of all samples gradually. The lowest flesh
firmness was obtained in fruits stored under MA conditions with 30% CO2 (30%-J and
30%-D). Date fruit at khalal stage had a hard and crisp texture and physico-chemical
changes that caused arising rutab spots, decreased fruit firmness. Fruits in the pouches
with 5% O2 (5%-J and 5%-D) and control (C) showed the highest firmness (2.1, 1.9 and
2.2 kg respectively).
Significant differences between the treatments were found in terms of titratable
acidity. TA level of date fruit in passive MAP (PM) and control (C) treatments were
consistently lower than those of the other treatments. At harvest, the levels of total acidity
(TA) calculated as malic acid was 22.48 mg/100 g fresh weight and TA increased
significantly throughout the evaluation period for all samples (Fig. 2e,f). At the end of the
experiment, pouches containing 30% CO2 recorded nearly 1.5-1.7 fold higher acidity of
the initial value. Also the results showed the fruits in pouches filled with 5% CO2 had
consistently lower acidity than those of treatments with 15 and 30% CO2. However,
detaching fruit from stalk, increased TA in 5 and 15% CO2 treatments, but it did not show
any significant effect on acidity levels. Similarly to rutab spots area, an increase in acidity
level was apparent during storage time and direct correlation was observed among these
studied parameters. Reversely, a gradual decrease in pH from 7.5 to 6.3 was seen during
the 28 days of storage (Fig. 2e,f). Pouches filled with 30% CO2 had maximum reduction
in pH.
The pattern of changes in flesh softening, reducing pH and rising acidity level in
fruits with high rutab spot area exhibit correlation with a high CO2 level and it can be

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concluded that the highest CO2 level (30%) is not appropriate for storage of date fruits at
khalal stage. This was nearly in contrast with the results of Al-Redhaiman (2004) that
reported khalal date fruits have significantly longer storage period under higher CO2
concentration.
Khalal fruits that lost their hard and crisp texture had lower quality and price.
Softening of fruit texture is related to activation of pectin decomposing enzymes. The role
of high CO2 level in slowing texture softening and other enzymatic reactions has been
underlined in different reports. Our results showed that CO2 at 30% concentration had a
negative effect on firmness due to stimulated fermentation, during that degradation of
hemicellulosic polysaccharides and cellulose, leads to disorganization of cell wall,
decrease in cellular turgidity and loss of texture firmness (Kader et al., 1989).
Increasing the acidity level upon storage and more specifically at the onset of
deterioration of fruit texture postulated the second generation of organic acids formation
(Barreveld, 1993). The accompanying increment of acidity level and brown surface
discoloration of fruits also suggested that organic acids can react with reducing sugars to
produce brown pigments (Lozano, 2006). Organic acids are a useful index of authenticity
in fruits and have an important influence on the sensory properties of fruits especially in
combination with sugars. Major organic acids that have been isolated from date flesh are
citric, malic and oxalic acid (Barreveld, 1993). Fruit juice pH is affected by alkaline and
acidic compounds of cells and any change in concentration of these compounds will
change the pH quickly (Wills, 1998). Barreveld (1993) reported the most common pH
values for ‘Deglet Noor’ date range from 5.3 to 6.3 and definite correlation was observed
between increasing the pH and the commercial quality for this cultivar.
The water activity value in ‘Barhee’ date fruits at the beginning of the experiment
was 0.97 (Fig. 2g,h). Evidently, after 28 days of storage, a slight decrease was observed in
this parameter in all treatments but with different rates. The highest rate of aw decline
during the storage period occurred in fruits stored under MA with 30% CO2 (0.94 in T5
and T6). On the contrary, the highest aw value was observed in fruits stored under MA
with 5% CO2. A clear correlation was identified between decrease in water activity and
rutab spots area, the less water activity, the higher Rutab spots (Aw = -0.0004 RSA +
0.9687). Water activity is the ratio of the partial vapor pressure of water in food to the
partial saturation vapor pressure of water vapor in the air at the same temperature and
describes the energy state of water in the food as an important quality factor for dates
during storage (Fontana, 2000). Decreasing the level of aw by storage duration revealed
bonding more H2O molecules to the solutes released from the fruit texture degradation.
As expected, significant changes in SSC were seen between different MAP
conditions applied. Fruits exposed to 30% CO2, displayed maximum amounts of SSC
(33.2 and 32.9 for 30%-J and 30%-D respectively). Generally, most of the full mature
khalal fruits gradually turned to low quality rutab fruits during storage. In all treatments
by increasing the storage period, a greater part of fruits turned to rutab, and SSC increased
from 27.7 to 34.3%. A direct correlation (SSC = 0.1039 RSA + 27.945) was observed
between SSC and RSA. The lowest amounts of increase in the SSC and RSA were seen in
pouches filled with 5% CO2, passive MAP and control (31.4, 32.8, 34.1 and 33.6%
respectively). SSC is one of the most important maturity and quality indices in various
fruits and in date fruits at khalal stage, should be more than 28% (Barreveld, 1993). In
contrast with produced rutab fruits in this work from khalal dates, the SSC content of
rutab date fruits naturally ripened on the tree is about 70% and those have an acceptable
quality. These findings are similar to those reported earlier by other workers on various
date cultivars (Barreveld, 1993). It is postulated that the immobile form of the ripening
enzymes existed in fruits harvested at khalal stage, is in contrast with dates left on the
palm till they turn naturally to rutab. Formation of some metabolites including soluble
contents arises by releasing and activating enzymes such as amylase, invertase,
polygalacturonase and polyphenol oxidases (Saleem et al., 2005).

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CONCLUSIONS
The date fruit of cultivar ‘Barhee’ lose their astringency at khalal stage and are
sold as fresh fruit. This stage will last for a couple of weeks, terminating the supply for
this purpose, leaving other fruits to mature further on the palm (Glasner et al., 2002). Fruit
at khalal stage has a limited shelf-life and generally is sold shortly after harvest and
mostly in the local markets. Based on our results we can conclude the significant
improvement in postharvest storage of khalal ‘Barhee’ date fruits that can be achieved,
under modified atmosphere conditions. Detrimental color changes of khalal dates were
related to packaging conditions and, CO2 injury was the direct result of the high CO2
levels. A conservative recommendation to minimize quality losses would be to keep the
khalal dates under 5% CO2 level during storage. However, the best beneficial effects were
obtained in active MAP, significant but not major differences were seen in passive MAP
conditions and due to lower costs, it can be recommended when needed. Detaching fruit
from stalk, showed negligible positive effects on maintaining the studied quality factors.
Evident correlations were displayed between RSA and firmness, acidity, water activity
and SSC postulated the biochemical changes of fruit issued from texture degradation by
means of different enzymes. To understand better these biochemical changes, research
dealing with and focused on the understanding of the processes involved might be
proposed.

ACKNOWLEDGEMENTS
We would like to thank the Departments of Horticultural Science and Food
Science & Technology, Tarbiat Modares University (TMU) for providing technical and
laboratory facilities, also the Date Palm and Tropical Fruits Institute of Iran in Ahwaz, for
providing fruit samples.

Literature Cited
Achour, M., Amara, S., Salem, N., Jebali, A. and Hamdi, M. 2003. Effect of vacuum and
modified atmosphere packaging on Deglet Nour date storage in Tunisia. Fruits
58:205-212.
Al-Redhaiman, K.N. 2005. Chemical changes during storage of ‘Barhi’ dates under
controlled atmosphere conditions. HortScience 40:1413-1415.
Barreveld, W.H. 1993. Date Palm Products. Agricultural Services Buletin No 101, FAO,
Rome, p.1-50.
Betts, G.D. 1996. A code of practice for the manufacture of vacuum and modified
atmosphere packaged chilled foods. Guideline No. 11, CCFRA, Chipping Campden,
Glos., UK.
Charles, F., Guillaume, C. and Gontard, N. 2008. Effect of passive and active modified
atmosphere packaging on quality changes of fresh endives. Postharvest Biology and
Technology 48:22-29.
Fontana, A.J. 2000. Water activity basics for safety and quality in food products. Second
NSF International Conference on Food Safety, October 11-13, Savannah, GA, USA.
Glasner, B., Botes, A., Zaid, A. and Emmens, J. 2002. Date harvesting, packinghouse
management and marketing aspects. p.237-267. In: A. Zaid (ed.), Date palm
cultivation. FAO Plant Production and Protection Paper, No: 156. FAO, Rome.
Kader, A.A., Zagory, D. and Kerbel, E.L. 1989. Modified atmosphere packaging of fruits
and vegetables. Crit. Review Food Science Nutrition 28:1-30.
Lozano, J.E. 2006. Fruit Manufacturing: Scientific Basis, Engineering Properties, and
Deteriorative Reactions of Technological Importance, Springer, 230p.
Mortazavi, S.M.H., Arzani, K. and Barzegar, M. 2007. Effect of vacuum and modified
atmosphere packaging on the postharvest quality and shelf life of date fruits in khalal
stage. Acta Hort. 736:471-477.
Rizzo, V. and Muratore, G. 2009. Effects of packaging on shelf life of fresh celery.
Journal of Food Engineering 90:124-128.
Rocculi, P., Romani, S. and Dalla Rosa, M. 2005. Effect of MAP with argon and nitrous

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 oxide on quality maintenance of minimally processed kiwifruit. Postharvest Biology
and Technology 35:319-328.
Saleem, S.A., Baloch, A.K., Baloch, M.K., Baloch, W.A. and Ghafoor, A. 2005.
Accelerated ripening of Dhakki dates by artificial means: ripening by acetic acid and
sodium chloride. Journal of Food Engineering 70:61-66.
Serrano, M., Martínez-Romero, D., Castillo, S., Guillén, F. and Valero, D. 2005. The use
of natural antifungal compounds improves the beneficial effect of MAP in sweet
cherry storage. Innovative Food Science & Emerging Technologies 6:115-123.
Wills, R., McGlasson, B., Graham, D. and Joyce, D. 1998. Postharvest: An Introduction
to the Physiology & Handling of Fruits, Vegetables and Ornamentals. CAB
International Press, Sydney, Australia, p.54-59.

Tables

Table 1. Weight loss modifications of different applied treatments during storage duration.

Storage duration
0 7 14 21 28
(days)
5%-J 0.00±0.00 0.45±0.02 0.62±0.09 0.94±0.23 1.58±0.25
5%-D 0.00±0.00 0.42±0.03 0.58±0.01 0.98±0.19 1.14±0.12
15%-J 0.00±0.00 0.42±0.03 0.61±0.02 0.73±0.12 1.82±0.34
15%-D 0.00±0.00 0.40±0.04 0.71±0.13 0.76±0.07 1.13±0.23
30%-J 0.00±0.00 0.39±0.02 0.68±0.09 0.74±0.13 1.28±0.19
30%-D 0.00±0.00 0.41±0.01 0.63±0.06 0.72±0.05 1.32±0.57
PM 0.00±0.00 0.39±0.02 0.60±0.09 0.81±0.06 1.23±0.18
C 0.00±0.00 3.17±0.86 5.50±0.39 8.91±0.97 10.48±2.46

Figures

70 25

60
20
CO2 concentration (%)

O2 Concentration (%)

50
15
40

30 10
20
5
10

0 0
Day 1 Day 7 Day 14 Day 21 Day 30 Day 1 Day 7 Day 14 Day 21 Day 30
Time of storage Time of storage

Fig. 1. Changes in CO2 (left) and O2 (right) partial pressure within pouches filled with
200±5 g of khalal date fruits as a function of time of storage, at 4°C, and
packaging condition: (5%-J) joint fruits+5% O2: 5% CO2; (5%-D) detached
fruits+5% O2: 5% CO2; (15%-J) joint fruits+ 5% O2: 15% CO2; (15%-D)
detached fruits+ 5% O2: 15% CO2; (30%-J) joint fruits+5% O2: 30% CO2;
(30%-D) detached fruits+5% O2: 30% CO2 and (PM) detached fruits in
passive MAP.

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Fig. 2. The effect of applied treatments (left) and storage duration (right) on different
quality attributes.

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