Ybc. Man et Mh. Moh, DETERMINATION OF FREE FATTY-ACIDS IN PALM OIL BY NEAR-INFRARED REFLECTANCE SPECTROSCOPY, Journal of the American Oil Chemists' Society, 75(5), 1998, pp. 557-562
A near-infrared (NIR) spectroscopy calibration was developed for the d
etermination of free fatty acids (FFA) in crude palm oil and its fract
ions based on the NIR reflectance approach. A range of FFA concentrati
ons was prepared by hydrolyzing oil with 0.15% (w/w) lipase in an incu
bator at 60 degrees C (200 rpm). Sample preparation was performed in D
utch cup, and the spectra were measured in duplicate for each sample.
The optimized calibration models were constructed with multiple linear
regression analysis based on C=O overtone regions from 1850-2050 nm.
The best wavelength combinations were 1882, 2010, and 2040 nm. Multipl
e correlation coefficients squared (R-2) were: 0.994 for crude palm oi
l, 0.961 for refined-bleached-deodorized (RBD) palm olein, and 0.971 f
or RED palm oil. Calibrations were validated with an independent set o
f 8-10 samples. R-2 of validation were 0.997, 0.943, and 0.945 respect
ively. The developed method was rapid, with a total analysis time of 5
min, and environmentally friendly, and its accuracy was generally goo
d for raw-material quality control.