| Summary: | 碩士 === 輔仁大學 === 食品科學系碩士班 === 105 === Cholesterol, widely present in the edible fat and animal tissues, can undergo oxidation to form cholesterol oxidation products (COPs) during heating. It has been well documented that the consumption of COPs in excess can be harmful to human health. The major COPs in foodstuffs include 7-ketocholesterol (7-keto), 7α-hydroxycholesterol (7α-OH), 7β-hydroxycholesterol (7β-OH), 5,6α-epoxycholesterol (5,6α-EP), 5,6β-epoxycholesterol (5,6β-EP), 25-hydroxycholesterol (25-OH) and cholestanetriol (triol). The objectives of this study were to develop a QuEChERS (quick, easy, cheap, effective, rugged, and safe) method for determination of COPs in edible oil and meat products by gas chromatography-mass spectrometry (GC-MS). By employing a DB-5MS capillary column (30m×0.25mm I.D., film thickness 0.25μm), 7 COPs, cholesterol and internal standard (5α-cholestane) could be separated within 20 min by using helium as carrier gas at a flow rate of 1 mL/min with the injector temperature at 280℃ and mass interface temperature at 300℃. The oven temperature programming was 250℃ in the beginning, raised to 290℃ at 10℃/min, maintained for 5 min, increased further to 291℃ at 0.1℃/min and maintained for 1 min. Samples were extracted with 20 mL of water/acetone (1:1 v/v), followed by adding magnesium sulfate and sodium acetate, vortexing for 1 min and centrifuging at 3200 g for 10 min. Then the supernatant was collected and mixed with primary secondary amine (PSA), magnesium sulfate and C18EC sorbent, and centrifuged at 3200 g for 10 min. Both limit of detection (LOD) and limit of quantification (LOQ) of COPs ranged from 0.16 – 180 ppb and 0.32 – 400 ppb, respectively, while the recoveries were from 89.1% – 107.6% for meat and 80.5% ~ 105.6% for oil. The intra-day variability ranged from 2.27% – 6.87% for meat and 1.52% – 9.78% for oil, whereas the and inter-day variability from 1.81% – 7.89% for meat and 3.57% – 9.26% for oil. Among the various meat, fish showed the highest level of COPs (31837 ng/g). For edible oils purchased from market, the COPs contents in contaminated lard (5533 ~ 16460 ng/g) and tallow (22794 ~ 70145 ng/g) were higher than in lard (153 ~ 2552 ng/g) and butter (534 ~ 1357 ng/g). However, no COPs were found in contaminated coconut oil and vegetable oil procured obtained from market.
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