Fig. 3. The ratio value in the fraction that results from each
crystallization process
Overall, the urea crystallization method was known to be able to provide
more effective and efficient purification compared to the acetone and
n-hexane crystallization methods. Urea crystallization was able to
maintain the presence of PUFA n-3 groups, especially EPA and DHA in the
fraction so that the levels increased [37]. Based on figures 2 and
3, the UPF fraction was very rich in n-3. UPF was able to increase the
PUFA/trans-FA ratio from 0.37 to 1.45 and n-3/trans-FA from 0.3 to 1.36.
The urea crystallization method proved to be able to produce fractions
very rich in n-3 fatty acids. Even so, this method still needs to be
further optimized because there was still an EA which has a higher
amount compared to EPA and DHA. As shown in Figure 3, the ratio of
EPA/EA and DHA/EA, although increasing, but still below one.
To eliminate EA completely, it is necessary to combine two purification
methods such as urea crystallization method with molecular distillation
which was able to separate EPA and DHA from sardine oil [38] or with
Argentated Silica Gel Column Chromatography which was able to separate
PUFA from tuna oil [36].
Conclusion
The urea crystallization method was significantly able to reduce the
content of SFA and EA (trans-FA), and be able to maintain n-3 PUFA
especially EPA and DHA in the oil fraction. Its seem from the increase
of ratio value of PUFA/trans-FA from 0.37 to 1.45 and n-3/trans-FA from
0.3 to 1.36. Even so, the crystallization of Urea has not completely
eliminated EA from the oil fraction. The only SFA that survived in the
three factions was lauric acid. Overall the Urea crystallization method
was able to recycle MAM became n-3 rich fraction.