Direct determination of the lipid content in starch-lipid composites by time-domain NMR

Starch-lipid composites, prepared by excess steam jet cooking aqueous mixtures of starch and lipid, are used in a broad range of applications for which their performance can depend upon accurately knowing the amount of the lipid contributed by the composites. A rapid and non-destructive method based on time-domain nuclear magnetic resonance spectroscopy (TD-NMR) was evaluated to quantitate soybean oil (SBO) or butterfat (BF) content in a series of dried starch-lipid composites. Transverse hydrogen relaxation (71,) properties of thc composites were examined using Carr, Purcell, Mieboom, Gill (CPMG) pulse experiments and multiexponential decay fitting routines were utilized to evaluate the various components. Spin-echo TD-NMR experiments were used to quantitate the amount of lipid in the composites and agreed well with lipid extraction experiments (R-2 = 0.998). Moisture levels in the composites were also simultaneously determined and compared reasonably well to moisture levels determined gravimetrically (R-2 = 0.881). TD-NMR was shown to be a rapid method to determine lipid and moisture content in these starch-lipid composites without the need for labor intensive extraction and gravimetric methods currently employed. (C) 2007 Elsevier B.V. All rights reserved.