Levels of phytosterol oxides in enriched and nonenriched spreads: application of a thin-layer chromatography-gas chromatography methodology

The content of phytosterol oxidation products (POPs) in enriched and nonenriched commercial spreads was evaluated by thin-layer chromatography-gas chromatography (TLC-GC). Oxides of beta-sitosterol, campesterol, and stigmasterol were produced by thermo-oxidation (7-hydroxy, 7-keto, and epoxy derivatives) and chemical synthesis (triol derivatives), which were then separated and identified by TLC-GC. Their identification was further confirmed by GC-mass spectrometry (GC-MS). The total amounts of phytosterols found were 6.07 and 0.33 g/100 g of sample in phytosterol-enriched and nonenriched spread, respectively, whereas the total POPs contents were 45.60 and 13.31 mg/kg of sample in the enriched and nonenriched products. The main POPs found were the 7-keto derivatives of all phytosterols analyzed; 7-ketositosterol was the most abundant one (14.96 and 5.93 mg/kg of sample in phytosterol-enriched and nonenriched spread). No beta-epoxy and triol derivatives were detected in both types of samples. The enriched spread presented a lower phytosterol oxidation rate (0.07%) than the nonenriched one (0.41%)

Thermo-oxidation of cholesterol: effect of the unsaturation degree of the lipid matrix

The influence of the unsaturation degree of different triacylglycerols (tristearin, triolein, trilinolein and trilinolenin) on cholesterol oxidation at 180 °C, was evaluated. Cholesterol degraded faster when heated alone than in the presence of triacylglycerols; moreover, the more unsaturated the matrix, the slower the degradation of cholesterol. Both cholesterol and triacylglycerols degradation fit a first order kinetic model (R(2)>0.9), except for the tristearin sample. Cholesterol oxidation products (COPs) and peroxides were formed during the heating treatment. The presence of any type of lipid matrix postponed and decreased the maximum concentration of both oxidation parameters. Maximum total COPs concentrations were achieved at 20 min in neat cholesterol, 120 min in tristearin and triolein and 180 min in polyunsaturated matrix samples. 7-Ketocholesterol was the main COP in most cases during the whole heating treatment. Both the presence of triacylglycerols and their unsaturation degree inhibited cholesterol thermooxidation at 180 °C

Levels of phytosterol oxides in enriched and nonenriched spreads: application of a thin-layer chromatography-gas chromatography methodology

The content of phytosterol oxidation products (POPs) in enriched and nonenriched commercial spreads was evaluated by thin-layer chromatography-gas chromatography (TLC-GC). Oxides of beta-sitosterol, campesterol, and stigmasterol were produced by thermo-oxidation (7-hydroxy, 7-keto, and epoxy derivatives) and chemical synthesis (triol derivatives), which were then separated and identified by TLC-GC. Their identification was further confirmed by GC-mass spectrometry (GC-MS). The total amounts of phytosterols found were 6.07 and 0.33 g/100 g of sample in phytosterol-enriched and nonenriched spread, respectively, whereas the total POPs contents were 45.60 and 13.31 mg/kg of sample in the enriched and nonenriched products. The main POPs found were the 7-keto derivatives of all phytosterols analyzed; 7-ketositosterol was the most abundant one (14.96 and 5.93 mg/kg of sample in phytosterol-enriched and nonenriched spread). No beta-epoxy and triol derivatives were detected in both types of samples. The enriched spread presented a lower phytosterol oxidation rate (0.07%) than the nonenriched one (0.41%)

Thermo-oxidation of cholesterol: effect of the unsaturation degree of the lipid matrix

The influence of the unsaturation degree of different triacylglycerols (tristearin, triolein, trilinolein and trilinolenin) on cholesterol oxidation at 180 °C, was evaluated. Cholesterol degraded faster when heated alone than in the presence of triacylglycerols; moreover, the more unsaturated the matrix, the slower the degradation of cholesterol. Both cholesterol and triacylglycerols degradation fit a first order kinetic model (R(2)>0.9), except for the tristearin sample. Cholesterol oxidation products (COPs) and peroxides were formed during the heating treatment. The presence of any type of lipid matrix postponed and decreased the maximum concentration of both oxidation parameters. Maximum total COPs concentrations were achieved at 20 min in neat cholesterol, 120 min in tristearin and triolein and 180 min in polyunsaturated matrix samples. 7-Ketocholesterol was the main COP in most cases during the whole heating treatment. Both the presence of triacylglycerols and their unsaturation degree inhibited cholesterol thermooxidation at 180 °C