Cholesterol oxidation in commercial samples of "pandoro" cake during the shelf life/Ossidazione del colesterolo in Pandoro nel corso della conservazione

This paper presents the study of the oxidative pathway of cholesterol through the determination of the cholesterol oxidation products (COPs) during the conservation of "pandoro", a traditional Italian vanilla cake. The cholesterol content of this product is about 0.7% of total lipids which, on its turn, represent about 23% of the cake. The determination of COPs was performed using gaschromatography after hydrolysis of the lipid extract, extraction of the unsaponifiable and purification with SPE. The identification of COPs was confirmed by means of GC-MS analysis. The samples of pandoro contained small amounts of COPs at the starting time (between 2 and 3 ppm of the product). Their concentration did not increase during the shelf life of the product, neither in the sample which was analysed one month after its expiration date. However, different pathways were observed for each determined compound: the 7 alpha -hydroxycholesterol content showed a constant increase, whereas 7-ketocholesterol was characterized by a variable trend of concentration. Both the isomers of epoxycholesterol decreased. Starting from the third month of conservation the 5 alpha -cholesten-3,5,6-beta -triol rapidly increased. Based on this result, a possible conversion of epoxycholesterol to cholestantriol during conservation can be confirmed.