Abstract:
The official methods (AOCS Ce1j-07 and Ce1h- 05), describe the methods for analyses of fatty
acids in specific fat sources and consists of several steps including GC temperature program to
resolve all fatty acids and the use of either theoretical correction factor (TCF) or empirical
correction factors (ECF) for flame ionization detector response of each fatty
acid. Determination of fatty acids in ready-to-eat diets using these GC temperature programs
have not consistently resolved the chromatographic peaks due to complexity of the matrix and
due to chromatographic conditions. This study aims to develop a temperature programme
specific to laboratory GC conditions to resolve the long chain fatty acids in ready-to-eat diets.
The laboratory optimized new programme (initial temperature of 90 °C increased to 140 °C
with 5 °C min-1
and then to 175 °C with 0.5 °C min-1
rate in turn increased to 220 °C at 20 °C
min-1
and held for 20 min ) has separated all 44 fatty acids in the reference standard mixture
(GLC 714, Nu-check prep, USA) with improved resolution and sensitivity, including co-eluted
polyunsaturated fatty acid pairs (C20:3n3, C20:4n6), (C20:4n6, C23:0), (C20:5n3, C24:0) and
(C24:1, C22:4) compared to AOCS conditions. Two types of diets, fried rice and rice and curry
(n=18), were randomly sampled from the Colombo municipal area and analyzed for fatty acid
composition using ECF and TCF separately, in the modified GC temperature program. The
NIST certified secondary reference material was used as a quality control sample. The test data
of fatty acids composition were revealed, that use of laboratory specific ECFs for determine
some of the saturated and monounsaturated fatty acids (between C4:0 to C18:0) including
C16:0, C17:0, are more accurate and reliable and also the modified temperature program is
able to analyse both saturated and higher chain polyunsaturated fatty acids with better accuracy
and sensitivity in the food matrix of ready-to- eat diets.
