Kinetic Parameters
The combinational kinetic model described by
Farhoosh (2018) was used to determine the
PV-based kinetic parameters. The kinetic curve of the accumulation of
LOOH molecules was drawn by plotting PV changes over time (Fig. 2). IP
(Eq. (4)) and CMC (Eq. (5)) of LOOH was calculated from the x- and
y-coordinates of the intersection point of two straight lines fitted on
the initiation and propagation stages of the kinetic curves,
respectively. The second straight line precisely arose from the
sigmoidal kinetic model (Eq. (6)) fitted on the whole range of PV
changes over time.
\(\text{IP}=\frac{K_{1}\ \left(2-\ K_{1}C_{c}+lnK_{2}\right)-4\text{PV}_{0}K_{2}}{4K_{i}K_{2}-\ k_{1}^{2}}\)(4)
\(CMC=K_{i}\left(\text{IP}\right)+\ \text{PV}_{0}\) (5)
\(\text{PV}=\frac{K_{1}\ }{\text{exp\ }\left[K_{1}\left(C_{c}-t\right)\right]+K_{2}}\)(6)
where ki (meq kg−1h−1), k1 (h−1) and
k2 (kg meq−1 h−1)
are the parameters of the equations; Cc (kg
meq−1) is an integration constant and
PV0 (meq kg−1) is PV at t = 0.
Antioxidative activities of alkyl gallate and gallic acid in bulk oil
peroxidation were examined by effectiveness factor (F ), oxidation
rate ratio (ORR), antioxidant activity (A ), and mean rate of
antiradical consumption
(\(\overset{\overline{}}{W}\)AH).
Stabilization factor (F ) or antioxidant efficiency, which showing
the potency of an antioxidant (AH) in delaying oxidation, was calculated
by Eq. (7).
\(F=\frac{\text{\ \ \ \ }\text{IP}_{\text{AH}}}{\text{IP}_{0}}\) (7)
where IP0 and IPAH are the IP in the
absence and presence of phenols, respectively.
The parameter ORR, which is inversely related to antioxidant power, was
determined by Eq. (8).
\(\text{ORR}=\frac{\text{\ \ \ \ }K_{i}}{\text{\ \ \ \ \ \ }K_{i0}}\)(8)
where Ki and Ki0 are the
pseudo-zero order rate constants in the presence and absence of phenolic
antioxidants, respectively.
Antioxidant activity (A ) was obtained with Eq. (9).
\(A=\frac{F}{\text{ORR}}\) (9)
The parameter \(\overset{\overline{}}{W}\)AH, the
average rate of AH consumption, was calculated by Eq. (10)
(Marinova and Yanishlieva, 2003).
\({\overset{\overline{}}{W}}_{\text{AH}}=\frac{\text{\ \ }\left[\text{AH}\right]_{0}\text{\ \ }}{\text{IP}_{\text{AH}}}\)(10)