Detection of adulteration of pumpkin seed oil by analysis of content and composition of specific Delta 7-phytosterols

A simple and accurate method for the determination of phytosterols by capil lary gas chromatography was developed for the analysis of the seeds and oil of the pumpkin Cucurbita pepo L., the naked seed variety growing in the so uthern Styrian parts of Austria. After extraction of the oil and saponifica tion, the remaining unsaponifiable material was isolated and purified using silica gel columns. For greater volatility, the sterols were derivatised t o trimethylsilylethers, and gas chromatography was performed on a column of high polarity, allowing separation of the Delta 5-sterols from the Delta 7 -sterols and thus yielding a typical chromatographical pattern. Quantificat ion of the phytosterols using 5 alpha-cholestan or cholesterol as internal standards led to a method of high accuracy. Comparison of the chromatograph ic pattern of the phytosterol fraction of pumpkin seed oil with those of ot her vegetable oil samples permitted the use of this method to detect adulte ration of pumpkin seed oil.