title: Cholesterol and stigmasterol within a sunflower oil matrix: Thermal degradation and oxysterols formation.
abstract: The characteristics of the lipid matrix surrounding sterols exert a great influence in their thermal oxidation process. The objective of this work was to assess the oxidation susceptibility of equal amounts of cholesterol and stigmasterol within a sunflower oil lipid matrix (ratio 1:1:200) during heating (180°C, 0-180min). Remaining percentage of sterols was determined and seven sterol oxidation products (SOPs) were analysed for each type of sterol along the heating treatment. Evolution of the fatty acid profile and vitamin E content of the oil was also studied. Overall oxidation status of the model system was assessed by means of Peroxides Value (PV) and TBARS. PV remained constant from 30min onwards and TBARS continued increasing along the whole heating treatment. Degradation of both cholesterol and stigmasterol fitted a first order curve (R(2)=0.937 and 0.883, respectively), with very similar degradation constants (0.004min(-1) and 0.005min(-1), respectively). However, higher concentrations of oxidation products were found from cholesterol (79μg/mg) than from stigmasterol (53μg/mg) at the end of the heating treatment. Profile of individual oxidation products was similar for both sterols, except for the fact that no 25-hydroxystigmasterol was detected. 7α-Hydroxy and 7-keto-derivatives were the most abundant SOPs at the end of the treatment. PUFA and vitamin E suffered a significant degradation along the process, which was correlated to sterols oxidation.
authors.affiliation: Department of Nutrition, Food Science and Physiology, Faculty of Pharmacy, University of Navarra, C/Irunlarrea s/n, 31008 Pamplona, Spain. Electronic address: bbarriuso@alumni.unav.es.
authors.forename: Blanca
authors.initials: B
authors.lastname: Barriuso
authors.affiliation: Department of Nutrition, Food Science and Physiology, Faculty of Pharmacy, University of Navarra, C/Irunlarrea s/n, 31008 Pamplona, Spain. Electronic address: dansorena@unav.es.
authors.forename: Diana
authors.initials: D
authors.lastname: Ansorena
authors.affiliation: Department of Nutrition, Food Science and Physiology, Faculty of Pharmacy, University of Navarra, C/Irunlarrea s/n, 31008 Pamplona, Spain. Electronic address: mpoyato@alumni.unav.es.
authors.forename: Candelaria
authors.initials: C
authors.lastname: Poyato
authors.affiliation: Department of Nutrition, Food Science and Physiology, Faculty of Pharmacy, University of Navarra, C/Irunlarrea s/n, 31008 Pamplona, Spain. Electronic address: iastiasa@unav.es.
authors.forename: Iciar
authors.initials: I
authors.lastname: Astiasarán
mesh_terms: D002784:Cholesterol / Q000032:analysis*; D005227:Fatty Acids / Q000032:analysis; D010545:Peroxides / Q000737:chemistry; D010938:Plant Oils / Q000737:chemistry*; D013265:Stigmasterol / Q000032:analysis*; D000074242:Sunflower Oil; D013696:Temperature; D014810:Vitamin E / Q000032:analysis
chemical_list: D005227:Fatty Acids; D010545:Peroxides; D010938:Plant Oils; D000074242:Sunflower Oil; D014810:Vitamin E; D002784:Cholesterol; D013265:Stigmasterol
keywords: Polyunsaturated fatty acids; Vitamin E