Analysis of phytosteryl and phytostanyl fatty acid esters in enriched dairy foods: A combination of acid digestion, lipid extraction, and on-line LC-GC

Qualitative and quantitative methods for the analysis of intact phytosteryl/phytostanyl esters in enriched dairy products with substantial amounts of protein and fat were established. Lipids were extracted after acid digestion in order to achieve a complete extraction of the esters. The extracted lipids were separated via liquid chromatography on a normal phase, and the fraction containing the phytosteryl/phytostanyl esters was subsequently transferred on-line and analyzed by means of capillary gas chromatography. The applicability of the method was demonstrated for the analysis of intact phytosteryl/phytostanyl fatty acid esters in enriched yogurt, cheese-based spread, and milk. The approach enables the determination of individual phytosteryl/phytostanyl esters as well as of their total contents and provides detailed information on the distributions of esterified phytosterols/phytostanols and fatty acids. The employed approach complements the existing GC-based methods for the analysis of phytosteryl/phytostanyl esters in low-fat and fat-based products and thus creates a base for authenticity assessments of these types of novel foods.