Extraction of fish oil was carried out by four different methods, i.e. by acid silages, microbial silages, cooking
and steaming using white sardinella (Sardinella albella). Among these methods, 74% of total oil was extracted
by the acid silage method and 52% of total oil was extracted by steaming compared to the yield from Bligh &
Dyer method on wet basis.
The proximate composition of forty seven different fish varieties were studied. According to these results and
on the basis of oil content, abundance and price value, four pelagics were selected for future studies. These are
white Sardinella (Sardinella albella), Thryssa.sp, Silverbeddy (Secutor ruconius) and Streaked sprinefoot (Siganus javus). The study extended to fatty acid assay of forty fish species revealed Yellowstripe scad
(Selaroides leptolepis), Dorab-wolf herring (Chirocenrus dorab). Spotted sardinella (Amblvsaster sirm). Blacktip sardinella (Sardinella melanura). Buccaneer anchovy (Slolephorus punctifer), Brushtooth lizard fish (Saurida undosquamis) and Big eye barracuda (Sphyraena forsteri) were rich in omega-3 polyunsaturates.
White sardenella and Tryssa.sp contained high quantities of oil during the months of November and February whereas the month of May showed the lowest reading. Relatively low amounts were in Silver belly (Secular
ruconius) and Orawa (Siganus javus) with no apparent seasonal peaks or troughs. In general, the oil content was
lower during the period April -June; the spawning season of most species falling in or around May.
Influence of temperature (33, 2 and -18°C) on the quality of fish and fish oil was studied using Sudaya
(S.albella). Oxidation was very rapid when stored at room temperature; ice storage maintained good quality
over a period of one month; freezing (-18EC) considerably slowed down undesirable quality changes. The
amount of oil extracted form frozen fish was little lower than that from unfrozen fish. During this 446 day
storage period, the amount of peroxides and free fatty acids increased while the omega-3 PUFA content slightly
decreased.
When the anti-oxidant property of some plant extracts in relation to rancidity was taken into consideration,
Indian Gooseberry (Nelli, Phynanthus emblica) showed the ability to offer highest protection for fish oil.
Active components in Indian Gooseberry, when extracted using Ethanol instead of water, produced better
results. Furthermore, the ethanolic extract was separated using different solvents with different polarity and the
best activity was recorded in ethyl acetate system with 0.58 relative polarity. This system recorded higher
activity at lOOQppm compared to 200ppm of BUT. Tamarind (Tamarindus indica) is yet anodier promising
anti-oxidant which can be used to stabilize fish oil.