Development and validation of methodologies for the quantification of phytosterols and phytosterol oxidation products in cooked and baked food products

Chromatography-​mass spectrometry (GC-​MS) methodologies for the anal. of the main phytosterols (PS) and phytosterol oxidn. products (POPs) present in 19 different foodstuffs cooked or baked using margarines with or without added plant sterols are presented. Various methods for fat extn. were evaluated to allow the GC-​MS anal. of large nos. of prepd. vegetable, fish and meat products, egg and bakery items in a practically feasible manner. The optimized methods resulted in a good sensitivity and allowed the anal. of both PS and POPs in the broad selection of foods at a wide range of concns. Calibration curves for both PS and POPs showed correlation coeffs. (R2) better than 0.99. Detection limits were below 0.24 mg kg-​1 for PS and 0.02 mg kg-​1 for POPs, resp. Av. recovery data were between 81​% and 105.1​% for PS and between 65.5 and 121.8​% for POPs. Good results were obtained for within- and between-​day repeatability, with most values being below 10​%. Entire sample servings were analyzed, avoiding problems with inhomogeneity and making the method an exact representation of the typical use of the food by the consumer.