Oxidation of cholesterol by heating

Abstract

Oxidation of pure cholesterol during heating in an air oven at high temperature was studied. Cholesterol was virtually stable during heating at 100 OC for 24 h but was unstable at temperatures above 120 OC. In the heated cholesterol preparations, a number of oxidized derivatives were detected by a combination of thin-layer chromatography and capillary gas chromatography-mass spectrometry. Major oxidized sterols were 7a-hydroxycho1estero1, 7,3-hydroxycholestero1, 5a-epoxycho1estero1, 5,3-epoxycholesterol, cholestanetriol, and 7-ketocholesterol. Various oxidized cholesterol derivatives were produced during heating above 120 "C within a relatively short time (1 h). The composition of the oxidized products differed depending on temperature and time of heating. When cholesterol was heated at 150 OC, the production of oxidized cholesterol was maximum, and 7-ketocholesterol was the most predominant oxidized product. Heating a t 120 OC also produced oxidized cholesterol to some extent, whereas only marginal amounts of oxidized cholesterols were produced a t 100 "C and at 200 "C cholesterol was almost decomposed in a short time.

Oxidation of β-sitosterol and campesterol in sunflower oil upon deep- and pan-frying of French fries

“…Regarding the OS of PS in vegetable oils, some aspects should be considered, such as the degree of unsaturation of the lipid fraction and the occurrence and type of antioxidants. Studies on the effects of co-oxidizing matrix lipids are controversial because some indicate that PS oxidation is enhanced by unsaturated lipids (Osada et al 1993), while others have shown that oxidation is more pronounced in saturated than in unsaturated lipid matrix (Lampi et al 2002). The high unsaturation level and tocopherols content of the lipid matrix, in SFO, might have a protective effect on PS oxidation.…”

Cholesterol oxidation: Health hazard and the role of antioxidants in prevention

“…Analytical procedures for the determination of the extent of cholesterol oxidation in food, especially in heated and/ or stored foods with high cholesterol content, include capillary gas-chromatography (GC) García & Maraschiello, 1997), GC-mass spectrometry (GC-MS) (Park & Addis, 1986;Osada et al, 1993), and high performance liquid chromatography (HPLC) . GC has been used by several researchers because it allows the rapid separation and identification of up to 17 different oxysterols.…”

Efeito do processamento sobre os níveis de colesterol e 7-cetocolesterol em camarão-rosa

“…A fritura aparentemente apresentava maior potencial para oxidação do colesterol porque a temperatura utilizada (140°C) é mais elevada que no cozimento (cerca de 100°C), aproximando-se da faixa de maior instabilidade do colesterol, 120 a 150°C [14,26]. No entanto, foi o processamento que levou à maior redução nos ní-veis de 7-cetocolesterol livre.…”

“…Estudos que avaliaram o efeito do processamento térmico sobre a formação dos óxidos de colesterol em alimentos sugerem que o tempo e a temperatura são fatores determinantes neste processo, influenciando diretamente a taxa de oxidação [12,21,26,31].…”

“…A presença de oxigênio, calor, radiação e metais de transição desencadeia o processo oxidativo [14,28]. Durante o processamento os alimentos são expostos a vários destes fatores.Dentre os produtos da oxidação do colesterol, o 7-cetocolesterol tem sido utilizado como indicador da oxidação do colesterol por ser produzido em maior quantidade e nos estágios iniciais do processo oxidativo [29,32,38,39].Estudos que avaliaram o efeito do processamento térmico sobre a formação dos óxidos de colesterol em alimentos sugerem que o tempo e a temperatura são fatores determinantes neste processo, influenciando diretamente a taxa de oxidação [12,21,26,31].Embora possuam atributos adequados para a formação de óxidos de colesterol, os produtos marinhos têm sido pouco estudados neste sentido. Moluscos e crustáceos apresentam níveis relativamente elevados de colesterol, além de possuírem alta proporção de ácidos graxos polinsaturados em sua fração lipídica [10].…”