Temperature dependent electrical conductivities of ginger paste during ohmic heating
the heating rate, product will be exposed to high
Data were analyzed statistically to see the effect of
temperature for shorter time duration preserving the
temperature, salt level and voltage gradients on time
product quality.
of heating of ginger paste. ANOVA (Table 4) shows
that temperature, voltage gradient, salt level and
their interactions had significant effect on total time
for heating of ginger paste. It can also be observed
that salt level affect more significantly than voltage
gradient and temperature which shows addition
of ions to the product increase the rate of heating
because of increasing electrical conductivity of
product.
The behavior of time of heating of ginger paste
under the influence of the temperature and salt level
for voltage gradient of 9 and 13 v/cm is depicted in
Figure 4 and Figure 5. It is observed from Fig that
Figure 2: Point electrical conductivity variation with
temperature and salt level
time of heating reduces with temperature increased
from 30˚C to 80˚C. Also heating rate found to be
increased with increasing voltage gradient. Relation
of temperature (T) at different time (t) and voltage
gradients can be represented by the equations given
in Table 5 with their R 2 values.
Figure 6 shows the heating behavior of ginger paste
in terms of heating rate. It can be observed from fig
that heating rate increased from 0.09 to 0.28˚C/s as
voltage gradients increased from 5 to 13v/cm. It was
also found that heating rate of ginger paste followed
linear trend with voltage gradients (R 2 = 0.99).
Figure 3. Bulk electrical conductivity variation with
temperature and salt level
Table 4. ANOVA for time of heating
Source
df
ss
ms
Fc
Ftab
Salt
Level
4
1401890 350472 544.79*** 3.44***
(A)
Voltage
2
60473
30236
47.00***
4.74***
Gradient (B)
Temperature
4
79461
19865
30.88***
3.44***
(C)
A×B
8
1221475 152684 237.34*** 2.63***
B×C
8
1071764 133970 208.250*** 2.63***
A×C
16
878006
54875
85.300*** 2.12***
Figure 4: Time of heating variation with temperature and salt
A×B×C
32
3627814 113369 176.226***
.80***
level at 9 v/cm
Error
150
96497
643.31
Total
224 8437382 37666
* = P<0.05, ** = P<0.01, *** = P<0.001
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