Thermo-oxidation of Cholesterol in Glyceryl Tristearate and Glyceryl Trioleate
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Abstract:
In order to elucidate the effects of saturation of fatty acids in triglycerides on cholesterol oxidation, thermo-oxidation of cholesterol in glyceryl tristearate(GTS) and glyceryl trioleate (GTO) was investigated by GC-MS, and their peroxide values were also measured. The results indicated that the main cholesterol oxidation products in GTS and GTO were 7α-hydroxycholesterol, 7β-hydroxycholesterol, 5,6β-epoxycholesterol, 5,6α-epoxycholesterol, and 7-ketocholesterol. At 160 ℃, the cholesterol oxidation products increased and then decreased over heating time, while unoxidized cholesterol reduced gradually in the process. The highest peroxide value (500.46 meq/kg) in GTO was achieved after 1 h heating. The peroxide value in GTS increased to the highest value of 401.30 meq/kg after 3 h heating, but then decreased with prolonging the treatment time. At 110 ℃, no cholesterol oxidation occurred in GTS, and the peroxide value kept lower, with its peak value (278.43 meq/kg) appearing after 96 h heating. However, cholesterol was almost completely oxidized in GTO, and the peroxide value increased rapidly, reaching its highest (1486.88 meq/kg) after 12 h heating, and then gradually decreased. Generally, cholesterol was more stable in GTS than GTO at 160 ℃ and 110 ℃, and the appearance of peroxide delayed with lower amounts. It was suggested that the saturated fatty acids in triglycerides were more beneficial to stabilize cholesterol under high temperature.
