Agriculture Reference
In-Depth Information
but it is a very expensive treatment and the product loses
much of its freshness with time. Hamad (2008) reported
that the spoilage of
Rutab
was mostly caused by mixed
populations of lactic acid bacteria, yeasts and molds, and
contamination with the pathogenic bacterium
Staphylococ-
cus aureus
and coliforms. The growth of microbes on dates
causes spoilage, while the pathogenic contaminants, espe-
cially at the
Rutab
stage, can cause illnesses, like poisoning
and infection.
Preservation of fresh dates (
Rutab
) by refrigeration was
not sufficient for storage as fungal attack was evident af-
ter few days of storage (Shubbar, 1980). Hassan et al.
(1980) indicated that potassium sorbate was most promis-
ing as antimicrobial agent when it was used on dates at
Rutab.
Some varieties like Barhi, at full mature stage of de-
velopment, initially have a moisture content about 65%
(El-Rayes and Ahmed, 2001). This moisture content is
comparatively much higher than the critical value of 23%
for yeast fermentation and fungal attack (Rouhani and
Bassiri, 1976). At this range of moisture, the CO
2
atmo-
sphere had shown to be fungicidal. The use of modified
atmosphere as a fungicidal agent is advantageous because
it is economically competitive with chemical fumigation,
and leaves no chemical residue on the fruit.
lene production and sensitivity to ethylene, reduced soften-
ing, and reduced decay (Kader et al., 1989). Active MAP
introduces a desired gas mixture into the package prior to
sealing, thereby accelerating the process in achieving an
equilibrium atmosphere (Zagory and Kader, 1988).
Storage for
Khalal
(
Bisir
)
Al-Redhaiman (2005) exposed full mature 'Barhi' date to
MA storage conditions with three carbon dioxide concen-
trations at cold storage (0
◦
C). Fruits stored under 20%
CO
2
showed significantly longer storage period (lasted for
26 weeks), and maintained better fruit quality, firmness,
and sensory properties than all other treatments (i.e., 5%
and 10% CO
2
, which lasted for 17 weeks) and the control
(lasted for 7 weeks). Moreover, fruits stored under MA con-
ditions showed lower decay and weight losses percentage.
It was quite clear that carbon dioxide at high concentration
(20%) significantly retarded fruit ripening, but did not cause
fruit injury. MA conditions prevented significantly tannin
degradation in date fruits during storage. Tannin contents
of date fruits are at maximum concentration in the
Kha-
lal
stage (full mature stage of development) and gradually
decrease to reach minimum concentration in the ripe stage
(
Rutab
). In another study, the physicochemical properties
of full mature 'Barhi' dates under two storage temperatures
(4
◦
and 25
◦
C) in response to vacuum and MA packaging
were studied (Mortazavi et al., 2007). Results showed that
fruits in MA treatment had less than 1% weight loss, lowest
percentage of
Rutab
fruits (14.7%), highest
a
w
(0.957), and
low changes in other parameters tested. However, in the
vacuum packaging, weight loss and the amount of crum-
bled fruits were least but a large portion of the fruit had
changed to
Rutab
(22.4%), and fruit firmness was signifi-
cantly reduced.
Aleid et al. (2010) observed the response of date
'Khalas' cultivar (at the late
Khalal
and early
Rutab
stages),
chilled (0
◦
C) overnight, before MA packing with varying
levels of carbon dioxide in air. Samples were assessed at
up to 27 days of chilled storage (0
◦
C). While by day 9, no
differences in color, sensory, and firmness were detected
between MAP dates and the control (cardboard carton),
by day 18, the MAP treatment retarded the fruit-ripening
process and then sustained fruit quality and firmness
(Fig. 10.5) compared to the control packaging. Control
date sensory scores were similar to MAP product up to
day 18 but dropped significantly by day 27. Sensory at-
tributes and firmness scores were however significantly
inferior for MAP dates with carbon dioxide levels above
20% by day 18. MAP treatment using CO
2
levels of 20%
or below demonstrated promising results for firmness and
DATE PACKAGING
In the packaging process, fumigated date is transferred to
a feeding line elevator and automatically dumped over a
shaker to preliminary washing. The shaker is provided with
water sprayers to remove initial load of dust and other
course foreign matters. Date is then sorted by passing
over a grading and sorting conveyer during which defected
and inferior dates are picked up from superior dates. Fruit
is finally washed in washing conveyer using fresh water
mixed with food-grade detergent, for example, superchlore
(sodium salt of dodecylbenzen sulfonic acid) and dubois
317 (di-methyl naphthalene sulfonate) as disinfectant. A
hot air blast is supplied to remove excess water, and the
date is then loose or press packed, sealed, wrapped, and
stored in cold storage (Mikki et al., 1986). In addition,
dates can be packaged in flexible plastic packages under
vacuum (Al-Hamdan and Hassan, 1998).
Modified atmosphere packaging
Modified atmosphere packaging (MAP) is now being used
to extend shelf life and reduce the wastage of a wide range
of fruits. In the MAP packaging systems, the gas mixture
surrounding fruits in the package is changed. Elevated con-
centrations of CO
2
and reduced levels of O
2
inside the
package have benefits including reduced respiration, ethy-
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