The Influence Of Priming Two Cucumber Cultivar Seeds

J. Duhok Univ. Vol.13, No.1, (Agri. And Vet. Sciences) Pp 139-147, 2010
Table(2): Rate constant(K) , half timr(t1/2) and activation energy(Ea) of ascorbic acid degradation for orange
juice model system stored in various.condition
Packaging materials Temperature ﻩ C Rate constant(K)
month -1
944
Half time(t1/2) month Activation energy(Ea)k.cal/mol
Glass bottle in light 20 0.119 5.819 7.791
Glass bottle in dark
Plastic bottle in light
Plastic bottle in dark
The activation energy value (Ea)for ascorbic
acid destruction(table 2), show that the values
indicated that samples stored in plastic bottles in
the light had marginally better retention of
ascorbic acid for samples in glass bottle in the
dark,hence Ea value of samples stored in glass
bottles in the dark was 13.437 k.cal.mol -1 but for
samples in glass bottles in the light was 7.791
k.cal.mol -1 .The higher degradation of ascorbic
acid stored in light condition samples in
comparision to samples stored in dark condition
was attributed to more light penetration through
clear bottles.This was perhaps due to synergistic
effect casued by combination of air trapped in
the headspace and dissolved in the samples and
that of light penetration through the bottles.The
results in the same table indicated that the
values of activation energy(Ea) of ascorbic acid
degradation of samples stored in glass bottles
was higher than samples stored in plastic
bottles.The( Ea )value of ascorbic acid
degradation samples for glass bottles stored in
dark was 13.43k.cal.mol -1 ,while for plastic
bottles stored in dark was10.99k.cal.mol -1 .This
results indicate that the material which presented
the best retention of ascorbic acid was glass
30 0.171 4.053
40 0.280 2.475
20 0.052 13.327 13.437
30 0.106 6.538
40 0.227 3.530
20 0.176 3.938 7.641
30 0.233 2.974
40 0.408 1.699
20 0.108 6.417 10.990
30 0.185 3.746
30 0.361 1.920
bottles comparision to plastic bottels.The plastic
bottles presented a poor retention of ascorbic
acid . Oxygen one of main factors that
contributes to ascorbic acid degradation.Results
indicate that glass was the material that presents
the lowest oxygen permeability comparision to
plastic.This results agrees with other researchers
(Alwazeer et al.,2003;Baiano and
Del.,2005;Muratore et al.,2005).
Considering the limit for shelf life of
model system indicative to ascorbic acid
degradation (table 3).Taking into account values
from all treatment it is observed that glass
bottles stored in light at 0 ° C hase a longer shelf
life (6.58 months) than those stored at 50 ° C
(0.72 month) when the lost of ascorbic acid was
25%, this mean the shelf life decreased with
increasing the temperature of storage.The results
in the same table indicated that the shelf life of
samples in glass bottles stored in dark have
longer shelf life (30.54 months) comparing with
those packed in glass bottles stored in light (6.58
months) when the lost of ascorbic acid was 25%
and stored at the same temperature (0 ° C).This
results agrees with other researchers as(Maria et
al,2001; Al-Zubaidy and Khalil,2007).