Agriculture Reference
In-Depth Information
Modified atmosphere for insect control
Changes in the atmosphere (oxygen depletion, carbon diox-
ide enhancement) have been noted to affect insect survival
(Soderstrom et al., 1990). A 4-hour exposure at 26 Cand
(2.8% O 2 in N 2 ) resulted in over 80% of the initial nitidulid
beetle populations emigrating from the infested dried dates
(Navarro et al., 1998a, 1998b). Al-Azab (2007) and Abo-
El-Saad (pers. comm.) used a mixture of modified atmo-
sphere (65% CO 2 , 15% N 2 , and 20% O 2 ) and found that an
exposure for 24 hours at 34 C and 65% relative humidity
gave 100% mortality against the adults of E. cautella. El-
Mohandes (2009) found that 100% mortality was achieved
after 36-hour exposure at CO 2 concentrations of 75% at
25 C and RH of 55% for the adults of Oryzaephilus suri-
namensis and Tribolium confusum. Moreover, application
of CO 2 at concentrations of 75% with half dose of PH 3 at
28 ±
microwave radiation (2540 MHz) were approximately 22
and 19 sec, respectively.
Irradiation for insect control
Irradiation is one of the possible alternatives to control in-
sects in dates. The use of irradiation to control insects in
dates and its effect on nutrients sensory and microbial of
dates have been investigated (El-Sayed and Baeshin, 1983;
Grecz et al., 1986; Al-Khahtani et al., 1998). It has been
found that irradiation of dates at 0.9 kGy was sufficient
to eliminate single insect infestation ( Orysaephilus surina-
mensis ) and mixed infestation ( O. surinamensis and T. cas-
taneum ) (Al-Khahtani et al., 1998). Total bacterial counts
were reduced significantly as compared to the reduction in
molds and yeasts since the latter are generally less sensitive
to irradiation (Jay, 1986). El-Sayed and Baeshin (1983) re-
ported that a dose of 25 Krad (0.25 kGy) of gamma ray was
effective in preventing the development of O. surinamen-
sis, E. cautella, and Batrachedra amydraula and feeding
damage in dates.
Irradiation (0.3 and 0.9 kGy) followed by 3 and 6 month
postirradiation storage at room temperature did not affect
the sensory properties of 'Khalas' dates (Al-Khahtani et al.,
1998). El-Sayed and Baeshin (1983) found no changes
in sensory quality of four irradiated varieties of dates at
0.2 kGy using Cobalt-60 gamma cell. In another work by
Grecz et al. (1986), panelist could not discriminate be-
tween unirradiated dates and those irradiated at levels of
1.0 to 6.0 kGy. Al-Khahtani et al. (1998) reported that fruc-
tose, glucose, and total sugars were significantly reduced
immediately after irradiation (0.9 kGy).
2 C and RH of 60%
5% caused 100% mortality
of both tested insects after 6 hours of exposure.
±
Microwave energy for insect control
In studies by Al-Azab (2007) and Abo-El-Saad (pers.
comm.), all stages of E. cautella (eggs, larvae, pupae, and
adults) were exposed to microwave energy at frequency
(2,450 MHz) for different time intervals (6-20 sec). The
data indicated that the application of microwave against E.
cautella stages gave 100% mortality for all stages within 20
sec (Fig. 10.4) with no adverse effect on glucose, fructose,
sucrose, and protein profiles. The sensitivity of all stages
to microwave energy was in the order of: pupae
>
>
adults
eggs (loaded on dates)
larvae. Wahbah (2003) reported
that the required exposure times for 50% mortality of the
two species O. surinamensis and T. castaneum in dates by
>
STORAGE OF DATES
Dates may be required to be stored for long periods of time,
up to 12 months. Temperature is the most important factor
that affects shelf life. During storage, dates are susceptible
to various quality problems, such as crystallized sugar
on the surface, excessive dryness of soft dates, hydration,
fermentation, and surface color change. Another common
storage problem is insect infestation (Mohsen et al., 2003).
Therefore the choice of appropriate humidity and temper-
ature conditions during storage is critical (Achour et al.,
1998). Moreover, preservation of dates by packing in sealed
plastic containers, or using polyethylene-polyamide (PE-
PA) bags under vacuum is a common packaging practice.
100
Larvae
Adults
80
60
40
20
0
02468 0
Time (seconds)
12
14
16
18
20
Refrigeration and freezing storage of dates
Fruits are living tissues and require cooling immediately
after the product is harvested to facilitate maintaining es-
sential freshness and nutritional values at the maximum
Figure 10.4. Effect of microwave energy on
E.cautellalarvae and adults in infested dates at
different exposure times (source: Abo-El-Saad,
2010).
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