Dates - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 176

dates because these dates are unfit for direct consumption.
The drying and quality tests led to the selection of a pre-
treatment step of soaking at 30 ◦ C for 8 hours, followed by
drying at an intermediate temperature (60 ◦ C) as the opti-
mum condition to obtain a final product of high quality with
35% moisture (Boubekri et al., 2010).
Dehydrated dates are used directly or as industrial ingre-
dients in the processing of various foods such as bakery
products and instant fruit powders (Mohamed et al., 2005).

To store dates for a long period (several months to a year),
fruit must be thoroughly cleaned of any pests (eggs, pupas,
larva, or adults), typically by fumigation with methyl bro-
mide. However, fumigation must not be carried out when
the fruit is fresh, harvested at the Khalal stage, or stored un-
der deep refrigeration. Methyl bromide is very effective for
controlling stored products insects, however, its emissions
are found to have a deleterious effect on the atmosphere,
and it is a tremendous hazard for human health; accordingly,
Montreal Protocol decided to eliminate its production and
use by the end of 2015 worldwide (CRA, 1985).
Alternatives for methyl bromide are (1) phosphine (PH 3 ),
which is the principal alternative to methyl bromide, (2)
controlled atmospheres high in carbon dioxide, and (3)
physical control methods such as filtering, heating or cool-
ing regimes, active-oxygen (ozone, hydrogen peroxide) and
irradiation. However, some of these methods are very costly
(Glasner et al., 2002). Heat treatment is a common way for
de-infestation of dates (Belarbi et al., 2001a, 2001b).
As an alternative to methyl bromide, Abo-El-Saad (pers.
comm.) accelerated aluminum phosphide (AlP) hydroly-
sis to produce phosphine gas by adding proton donors
such as 2N HCl, 5% acetic acid or water which individ-
ually added to AlP at ratio of 1:1 (v/w), the PH 3 gas was
produced immediately and gave a 100% mortality against
thelarvaeof E. cautella within 2 hours of exposure time
instead of 3-7 days under nonaccelerating condition, as
shown in Fig. 10.3.

Microwave drying
Idris and El-Gassim (1993) and El-Sharnouby et al. (2007)
studied the effect of four different drying methods (oven,
microwave oven, solar energy, and oven under vacuum)
on the quality of date's powder. There were differences
in total sugars, crude protein, fiber, ash, and vitamin C (as
ascorbic acid) among powders produced by different drying
methods. Date powders dried by microwave oven had the
highest rehydration ratio (1:5) and were more acceptable
than other powders produced by other methods.

Rutab drying
Some date varieties in the Rutab stage with high mois-
ture content of 28-32% suffer from a periodic surplus
problem because they tend to drop before reaching Ta m a r
stage. They are produced in comparatively short peri-
ods and are highly perishable. Fooladi and Tafti (2003)
dehydrated Rutab at 50 ◦ -55 ◦ C and 10-15% RH up to
24 hours in drying room. During drying process, the
acidity content was gradually increased but organoleptic
properties decreased, especially after 12 hours of dry-
ing time and in moisture of content of < 22%. Drying
rate of Rutab depends on factors such as texture, drying
temperature, and speed of air circulation. Drying time of
9-12 hours and acceptable moisture content of 22%
were recommended. Rutab with high moisture content
(above

120

100

80

22%) are prone to microbial growth (Fooladi and
Tafti, 2003).

∼

60

40

Insect control in dates
Fumigation for insect control
The date industry suffers terribly from the ravages of in-
sects. Infestation of dates with moths (almond moth, meal
moth), beetles (sap beetle, saw-toothed grain beetle, flour
beetle), fig moth, Ephestia cautella, and the Indian meal
moth, Plodia interpunctella, rats, mice, and ants lead to
contamination and loss of volume (Morton, 1987; Glas-
ner et al., 2002). The presence of the larvae inside the
dates gradually reduces their market value (El-Sayed and
Baeshin, 1983).

20

0

0 0 0 0 0
Time (minutes)

80 100 120

Figure 10.3. Effect of hydrolyzed aluminum
phosphide (AlP) under accelerating conditions by
mixing with water against E.cautellalarvae-infested
date at different exposure times (source:
Abo-El-Saad, 2010).