Cholesterol and stigmasterol within a sunflower oil matrix: Thermal degradation and oxysterols formation
Keywords: 
Polyunsaturated fatty acids
Vitamin E
Sterols
Issue Date: 
2015
Publisher: 
Elsevier
ISSN: 
0039-128X
Citation: 
Barriuso B, Ansorena D, Poyato C, Astiasarán I. Cholesterol and stigmasterol within a sunflower oil matrix: Thermal degradation and oxysterols formation. Steroids. 2015;99:155-160
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 ºC, 0 to 180 min). Remaining percentage of sterols was determined and seven sterol oxidation products (SOPs) were analyzed 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 Peroxide Value (PV) and TBARS. PV remained constant from 30 min onwards and TBARS continued increasing along the whole heating treatment. Degradation of both cholesterol and stigmasterol fitted a first order curve (R2= 0.937 and 0.883, respectively), with very similar degradation constants (0.004 min-1 and 0.005 min-1, respectively). However, higher concentrations of oxidation products were found from cholesterol (79 μg/mg) than from stigmasterol (53 μg/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-ketoderivatives 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.

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