Calibration of near infrared spectroscopy for solid fat content of fat blends analysis using nuclear magnetic resonance data

The functional properties of fats are determined by the distribution pattern of fatty acid residues in their acylglycerols, which may be modified by ester interchange (transesterification). In the margarine industry, the time course of the transesterification of fat blends is monitored by assaying for the amount of the solid fraction at different temperatures (SFC-solid fat content) currently measured by nuclear magnetic resonance (NMR). The aim of this study was to evaluate the feasibility of near infrared spectroscopy (NIRS) to quantify the SFC of different fat blends using NMR data for calibration. SFC values of 128 samples, consisting of different blends of palm stearin, palm kernel oil and concentrates of triglycerides enriched with omega-3 polyunsaturated fatty acids were assayed by NMR prior to (64 samples) and following inorganic (10 samples) or lipase-catalysed transesterification (54 samples). Prior to SFC measurement by NMR, sample preparation takes about 90 min. With NIRS technique, a faster determination is achieved since NIR spectra for SFC estimations are directly obtained on the sample at room temperature. High correlations were obtained for cross-validation of the data estimated by NIRS models and NMR for SFC assays at 10 degrees C (R-2 = 0.91, RMSECV = 2.4), 20 degrees C (R-2 = 0.96, RMSECV = 1.7), 30 degrees C (R-2 = 0.96, RMSECV = 1.3) and 35 degrees C (R-2 = 0.96, RMSECV = 1.3) of the different blends tested. The obtained results show that NIRS is a reliable technique to replace NMR for SFC estimation. (c) 2005 Elsevier B.V. All rights reserved.