3 Results
3.1 Selection of Favors
The pAV of flavored fish oils were consistently higher than the pAV of
the unflavored control oil. However, the magnitude of this pAV
difference varied (Fig. 1). Among all the flavors screened,
chocolate-vanilla and lemon flavors caused the greatest change in pAV.
Therefore, these flavors were selected for further analysis.
3.2 Compound Identification in Chocolate-Vanilla and Lemon Flavors
Although there were only six compounds identified in chocolate-vanilla
flavor with peak areas > 1% of the internal standard
(Table 1), three of them (p -anisaldehyde, piperonal, and
vanillin) were aldehydes that have a great potential to condense with
the p -anisidine reagent and increase the pAV. Among the six
identified compounds, the three aldehydes also had the highest area
relative to the internal standard (ARIS), with p -anisaldehyde,
piperonal, and vanillin at 4.7%, 24.5%, and 90.7%, respectively. A
small amount of trimethylpyrazine, ethyl caprylate, and ethyl caprate
were also identified. On the other hand, 15 compounds were identified in
lemon flavor, but there were still only three aldehydes (decanal,
β-citral, and α-citral) that had potential to react withp -anisidine. Decanal, β-citral, and α-citral had ARIS of 2.1%,
19.2%, and 29.6%, respectively. Total ARIS of the three aldehydes in
the chocolate-vanilla flavor was much larger than the three aldehydes in
lemon flavor. Besides aldehydes, a large amount of terpenes was also
identified in the lemon flavor. Limonene and β-pinene had ARIS of
824.5% and 123.0% respectively.
3.3 Oxidation of Chocolate-Vanilla and Lemon Flavored Fish Oils
The pAV of all the fish oil samples increased over the course of the
20-day study at 40°C (Fig. 2). In chocolate-vanilla flavored oils, a
significant difference in pAV was found between FBO and FAO samples on
Day 20. In lemon flavored oils, a significant difference in pAV occurred
between FBO and FAO since Day 12. According to regression analysis, an
exponential model was best fitted to the pAV data of each treatment
(R2 = 0.961 - 0.975). In both chocolate-vanilla
and lemon flavored oils, A (stable interfering aldehydes) was
significantly higher in FBO and FAO than in UFO (Table 2). No
differences were detected in B (changing aldehydes). In the
chocolate-vanilla flavored fish oils, FBO samples had a significantly
lower k (rate constant) than UFO. In lemon flavored oils, no
significant difference was detected in the k of UFO, FBO, and
FAO.