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

Abstract

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 ( T 2) properties of the composites were examined using Carr, Purcell, Mieboom, Gill (CPMG) pulse experiments and multi-exponential 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.