Development Of A Direct Transesterification ]\Tlethod For The Determina Tion Of Total Fa Tty Acid Content In Oils, Meals And Tissues Of African Catfish
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Date
2004-02
Authors
INDARTI, ETI
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Abstract
This research was carried out to develop a direct transesterification (DT) method
for the preparation of fatty acid methyl esters (FAME) suitable for chromatographic
analysis of total fatty acids in oils, meals and fish tissues. The DT method that was
developed utilized a 4 ml reagent consisting of methanol:H2S04:chloroform
(1.7:0.3:2.0, v/v/v) in which the sample was heated for a specific time period. The
organic phase containing FAME was then subjected to gas chromatography (GC)
analysis.
For fish oil and cod liver oil, the total fatty acid (TF A) recovenes were
optimized at heating 90°C for 90 min or 100°C for 30 min, while the highest TF A
recoveries from lipid-in-feed ingredient samples such as fish meal and poultry offal
meal were observed either at 90°C for 90 min or 100°C for 60 min. Under optimum
conditions, TF A recoveries were above 95%, which reflected satisfactory quantification
of total fatty acids. For reasonable chromatographic appearance and efficient TF A
recovery, sample size of 20 mg was adequate for oils, 50 mg for samples with lipid
content above 10%, while 100 mg was required for samples containing lipid below
10%. The composition of fatty acids was found to be independent of heating time and
temperature for any type of sample. Also, qualitative analysis can be performed only
within half an hour.
Compared with the conventional method, the DT method resulted in enhanced
TFA recoveries by 20.4-21.3% for oil samples, 18.7-21.4% for meal samples, and 23.0-
29.4% for freeze-dried muscle, while the fatty acid composition between these methods
, were comparable. Reduced TF A recoveries with the conventional method were due to r losses by evaporation and possibly oxidation of fatty acids and FAME in extraction and
transesterification. The DT method offers some practical benefits such as short
processing time, small sample size and small volume of reagents and solvents and thus
reducing chemical costs and waste.
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Development Of A Direct Transesterification ]\Tlethod For The Determina Tion , Of Total Fa Tty Acid Content In Oils, Meals And Tissues Of African Catfish