Factors affecting sample preparation in the gas chromatographic determination of plant sterols in whole wheat flour

A fractional factorial experimental design was applied to study factors affecting sample preparation prior to a gas chromatographic determination of total plant sterols in cereal samples. Whole wheat flour was chosen for the representative matrix. Altogether six factors were studied at two levels. The most affecting factors were a type of hydrolysis (combined acid hydrolysis and alkaline hydrolysis over alkaline hydrolysis alone), extraction solvent after saponification (chloroform over hexane–ether), and sample amount (1.0 g over 2.0 g). Also, it was shown that there is no need to perform total lipid extraction prior to hydrolysis. The use of acid hydrolysis prior to alkaline saponification was found to be essential in a plant sterol analysis of flour matrix. In a further method development, that procedure is to be optimized with various foods of plant origin in order to establish a general method to determine plant sterols. Toivo et al., Factors in the determination of plant sterols