Composição de acidos graxos e quantificação dos acidos graxos LNA, EPA e DHA no tecido muscular de tilapias (Oreochromis niloticus), submetidas a diferentes tratamentos com oleo de linhaça. / Fatty acid compositionand and quantification one of LNA, EPA and DHA in the fabric muscular of tilapias (Oreochoromis niloticus), submitted the different treatments with linseed oil.

Jesui Vergilio Visentainer

The present work had as its aim to raise the omega-3 (@-3 or n-3) fatty acids content in farm fish. With this in mind young Tilapias (Oreochromis niloticus) samples weighing approximately 88g were taken randomly to captivity in an experiment with four treatments (B, C, D and E) using linseed oil and one control (treatment A) using sunflower oil. The rations with linseed oil received increasing levels of it, being used because of its high level of alpha-linolenic acid (ALA, 18:3n-3), a precursor of other fatty acids of the n-3 family with a high nutritional interest. The sunflower acid used in the control ratio was chosen because of its low levels of ALA acid. The fatty acids composition, moisture and total lipids in the ratios were monitored during the supplying period. After five months of captivity in asbestos-cement boxes (water capacity of 1000L), the tilapias were slaughtered, the filets removed and taken to both moisture and total lipid (TL) determination. In the TL, it was analyzed the composition of fatty acids and the quantification of ALA (18:3n-3), eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) acids in mg/gram of TL using methyl ester of tricosanoic acid as an internal pattern. The TL were still fractioned in neutral lipids (NL) and phospholipids (PL) through classical column. The methyl esters separation of samples of TL, NL, PL and the content of ALA, EPA and DHA was carried out by gas chromatography, in fused-silica capillary column DB-WAX-20M, of 30m x 0.25mm x 0.25?m, kept at 170oC for 16 minutes, programmed at 2oC per minute up to 210oC, being kept at his temperature for 30 minutes, with injector at 250oC and detector at 280oC, using hydrogen as a dragging gas at 1mL/min. In TL, NL and PL, a total of 50, 64 and 58 components were found, respectively. The major fatty acids were the linoleic (18:2n-6), oleic (18:1n-9) and palmitic (16:0), where some times an inversion of these values occurred in some treatments and fractions. The fatty acids sums of the n-3 family in TL, NL, and PL were always increasing, whilst the sums of the n-6 family were always the opposite. The difference was significant for most of the treatments in both families as the linseed oil level increased in the rations. In the PL fraction, for the same treatment, the sums of the n-3 family fatty acids were always higher in relation to the sums in TL and NL. In TL, the supply of linseed oil based rations contributed for a better nutritional value of the meat lipid content (muscular tissue) in various aspects: it always furnished higher fatty acid content of ALA, EPA and DHA, increasing the sum of n-3 family fatty acids, reducing the ratio value of n-6/n-3, and, still increasing the values of HUFA/SFA and PUFA/SFA ratios. In the fatty acids quantification (ALA, EPA and DHA) in mg/g of TL, it was well established the concentration increase of these acids as they had their linseed oil level increased in the rations. The concentration values of ALA, EPA and DHA acids in mg/g of TL varied between the treatments A and E from 6.52 to 59.28 (ALA), from 0.15 to 2.54 (EPA) and from 9.93 to 26.13 (DHA). At the sensorial analysis, it was used the method of simple-triangular difference between the commercial tilapias filets and those which received rations with a higher content of linseed oil (treatment E). It was not found a significant difference in flavor between the filets.

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