Application of standard addition to eliminate conjugated linoleic acid andother interferences in the determination of total trans fatty acids in selected food products by infrared spectroscopy
Mm. Mossoba et al., Application of standard addition to eliminate conjugated linoleic acid andother interferences in the determination of total trans fatty acids in selected food products by infrared spectroscopy, J AM OIL CH, 78(6), 2001, pp. 631-634
A novel and rapid (5 min) attenuated total reflection-fourier transform inf
rared (ATR-FTIR) spectroscopic method AOCS Cd 14d-99 for the determination
of total isolated trans fatty acids, which absorb at 966 cm(-1), was recent
ly developed, collaboratively studied, and applied to food products contain
ing 1-50% trans fat (as percentage of total fat). Attempts to apply the ATR
-FTIR method to biological matrices of low trans fat and/or low total fat c
ontent, and to dairy and other products were not satisfactory due to interf
ering 1R absorptions in the trans region. One group of interfering compound
s with absorption bands near 985 and 948 cm(-1) was the cis/trans positiona
l isomers of conjugated linoleic acid (CLA) found in dairy and meat product
s from ruminants at levels of <1% (as percentage of total fat). In the pres
ent study, we modified the ATR-FTIR method to overcome matrix interferences
. This modification, which consisted of applying the standard addition tech
nique to the ATR-FTIR determination, was also applied to several food produ
cts, namely, dairy products, infant formula and salad oil dressing, which s
uccessfully eliminated interfering absorbances that impacted on accuracy. T
he presence of <1% CLA in two butter and two cheese products containing 6.8
, 7.5, 8.5, and 10.4% trans fatty acids (as a percentage of total fat) woul
d have led to errors of -11.6, 10.4, 17.6 and 34.6%, respectively, in trans
fat measurements had the standard addition technique not been used. The ap
plicability of ATR-FTIR to the quantitation of food products is discussed.