Total plant sterols, steryl ferulates and steryl glycosides in milling fractions of wheat and rye

Abstract

The total plant sterol, steryl ferulate and steryl glycoside contents in wheat and rye milling fractions show that there are significant differences in both sterol content and composition between various milling fractions collected from a commercial mill. Total sterols were analysed by gas chromatography after acid and alkaline hydrolyses. The steryl conjugates were first extracted with acetone, fractionated on solid phase extraction (SPE) cartridges and then analysed individually (steryl glycosides by gas chromatography and steryl ferulates by reverse phase-high performance liquid chromatography with UV detection. Differences in sterol contents of the wheat samples were greater than in the rye samples. The highest total sterol content was found in wheat germ, but surprisingly high sterol contents, that were comparable to bran, were found in some flour fractions. Contents of steryl ferulates were high in the bran fractions contributing up to 17% of total sterols. The variation in the content of steryl glycosides in the samples was lower and contributed less than 10% of total sterols. These results show that much of the bioactive components may be lost when certain flour fractions produced in common flour milling procedures are discarded. However, some of these fractions with significantly high sterol contents could possibly be introduced into milling products used in breadmaking and the food industry without greatly compromising consumer acceptability.