have been reported by Cakli et al. (2006). TBA index value
of control group increased during storage. Similar results
were determined in RO, TO, SO and CO groups. Lower
production of TBA index values SO and CO groups may be
due to the antioxidant properties of sage oil and clove oil
(Toda et al. 1994: Fasseas et al. 2007). The decrease in TBA
index values may represent the breakdown of the molondialdehyde
to tertiary degradation. After the 14th day, the
differences between the control group and treated groups
were found to be statistically significant (p<0.05). Yu et al.
(2002), Quitral et al. (2009) and Erkan and Bilen (2010)
observed that a rosemary, thyme and sage oil was an effective
means of controlling lipid oxidation in fish meat, as
reflected in thiobarbituric acid reactive substance values.
Shelf life of oil fish species is limited due to the oxidation
of lipid. The primary product of lipid oxidation is fatty acid
hydroperoxide, measured as PV. Peroxides are unstable
compounds, and they break down to aldehydes, ketones
and alcohols that are volatile products causing off-flavour
in products (Ucak et al. 2011). PV value in the fillet was
detected to be 1.17±0.19 (millimole O2/kg). After smoking
PV for hot smoked fillets were 1.17, 1.27, 1.22, 0.90 and
1.04 millimole O2/kg for the control, RO, TO, SO and CO
respectively (Fig. 2). During storage period, increase in PV
was observed for all groups. Significantly higher PV (p<
0.05) was obtained from the control group (A). No significant
differences (p>0.05) of PV was found for treated until
42nd day. These results proved that essential oils were
effective on PV. The results of this study are similar to the
findings of Quitral et al. 2009; Shahidi et al. 1995 and
Perez-Mateos et al. 2006. During storage period, the lower
PV was observed for Group CO.
Free fatty acids (FFA) are formed by lipolysis of triglycerides
and phospholipids (Pearson et al. 1983). The increase in
free fatty acid amount in the composition of foods is one of the
factors that accelerate oxidation. FFA amount in the fillet was
detected to be 0.63±0.07, which was approximately similar to
the values reported for Sardine pilchardus (0.53%oleic acid),
for Scomber japonicus (1.64 % oleic acid) (Soyer and Şahin
1999). At the beginning of the storage period (after smoking),
FFA amount of hot smoked rainbow trout were determined as
0.76, 0.68, 0.75, 0.70 and 0.76 (oleic acid %) for the control,
RO, TO, SO and CO respectively. FFA increase in the control
group was higher than treated groups during storage. After the
14th day, the difference between the control group and treated
groups was found to be significant (p<0.05). At the end of the
storage period of 112 days, FFA amount of CO group was
found to be 3.79 (oleic acid %). The results established the
antioxidant characteristics of the essential oils. Olley et al.
1969; Frega et al. 1999; Serdaroglu and Felekoglu 2005
confirmed the findings of our study. This result can be
explained by increasing free fatty acids (FFA) levels due
to the enzymatic hydrolysis during storage (Hwang and
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