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Free fatty acid formation and lipid oxidation on milled rice
Author(s) -
Lam Henry S.,
Proctor Andrew,
Meullenet JeanFrançois
Publication year - 2001
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11745-001-0425-6
Subject(s) - partial least squares regression , fatty acid , chemistry , lipid oxidation , food science , infrared , aldehyde , analytical chemistry (journal) , chromatography , biochemistry , mathematics , optics , antioxidant , statistics , physics , catalysis
Milled rice was stored at 37°C and 70% humidity and sampled regularly for 50 d. Rice surface lipid was extracted with isopropanol and analyzed for free fatty acids (FFA) and conjugated diene (CD) contents. Diffuse reflectance Fourier transform infrared (DRIFTS) spectra of the rice samples were also obtained. FFA and CD levels increased together during rice storage and exhibited three distinct phases. DRIFTS identified a decrease in intensity at 1746 cm −1 (ester, −C=O) and increases in intensity at 1731 cm −1 (aldehyde, −CO) and 1714 cm −1 (fatty acid, −C=O) during storage, which correlated well with the chemical analysis data. DRIFTS spectral data were analyzed by a partial least squares regression method to identify spectral regions that correlate strongly with measured FFA and construct prediction models. Overall, the mid‐infrared region (4000–400 cm 1 ) gave the best model ( R =0.98, root mean square error of cross‐validation=0.05) and also predcted the FFA content of milled rice well. The DRIFTS technique has potential for use in studying qualitative chemical changes on the milled rice surface lipids and for predicting FFA on milled rice.