Page 400 - Biosystems Engineering

Extraction, Refining, and Stabilization of Edible Oils 377

Crude oil becomes lighter in color during the course of experiment.
According to Beer–Lambert’s law, adsorption is proportional to the
concentration, which is as follows: 15
lnA/A = – kt (13.2)
0
where A is the absorbance of the colorants at time t and A is the
0
absorbance of the colorants at t = 0. If we plot lnA versus t according
to Eq. (13.2), the slope of the curves gives the value of k.
The activation energy can be determined by the Arrhenius
equation 15
k = Ae –E a /RT (13.3)
where k = rate constant
A = frequency factor or the Arrhenius constant
E = activation energy
a
–1
–1
R = universal gas constant (8.314 JK mol )
T = absolute temperature
When lnk is plotted against the reciprocal of the temperature (1/T),
– E /R represents the slope and the intercept gives ln A. The thermo-
a
dynamic parameters are assigned to activated complex as follows:
ΔH = E – RT (13.4)
a
Here, ΔH represents the activation enthalpy change of the oils;
these values are represented in Table 13.2. The negative value of ΔH
indicates that energy is released during the adsorption process (i.e.,
this adsorption process is an exothermic one). ΔS represents the acti-
vation entropy change; its values are calculated at different tempera-
tures [Eq. (13.5)] as follows:

A = RT/Nhe ΔS/R (13.5)

–1
Name of Oil Temperature (°C) ΔH (KJ/mole) ΔS (KJ /mole)
Bahera oil 30 –2.503 –22.80
60 –2.752 –19.96
75 –2.877 –18.74
Mustard oil 30 –2.506 –16.81
60 –2.755 –14.55
75 –2.880 –13.56
Sesame oil 30 –2.505 –14.17
60 –2.754 –12.10
75 –2.879 –11.27

TABLE 13.2 Measurement of ΔH, ΔS at Different Temperatures of Bahera,
Mustard, and Sesame Oil