Bortolomeazzi Renzo, Cordaro Francesca, Pizzale Lorena, Conte Lanfranco S
Food Science Department, Udine University, via Marangoni 97, 33100 Udine, Italy.
J Agric Food Chem. 2003 Apr 9;51(8):2394-401. doi: 10.1021/jf026063d.
The content of phytosterol oxidation products was determined in samples of crude vegetable oils: peanut, sunflower, maize, palm nut, and lampante olive oils that were intended for refining and not for direct consumption. The 7 alpha- and 7 beta-hydroxy derivatives of beta-sitosterol, stigmasterol, and campesterol and the 7-keto-beta-sitosterol were the principal phytosterol oxides found in almost all of the oils analyzed. In some oils, the epoxy and dihydroxy derivatives of beta-sitosterol were also found at very low levels. The highest total concentrations of phytosterol oxides, ranging from 4.5 to 67.5 and from 4.1 to 60.1 ppm, were found in sunflower and maize oils, respectively. Lower concentrations were present in the peanut oils, 2.7-9.6 ppm, and in the palm nut oil, 5.5 ppm, whereas in the lampante olive oils, only three samples of the six analyzed contained a low concentration (1.5-2.5 ppm) of oxyphytosterols. No detectable levels of phytosterol oxides were found in the samples of palm and coconut oils. Bleaching experiments were carried out on a sample of sunflower oil at 80 degrees C for 1 h with 1 and 2% of both acidic and neutral earths. The bleaching caused a reduction of the hydroxyphytosterol with partial formation of steroidal hydrocarbons with three double bonds in the ring system at the 2-, 4-, and 6-positions (steratrienes). The same sunflower oil was deodorized at 180 degrees C under vacuum for 1 h, and no dehydration products were formed with a complete recovery of the hydroxyphytosterols. A bleaching test with acidic earths was carried out also with an extra virgin olive oil fortified with 7-keto-cholesterol, dihydroxycholesterol, and alpha-epoxy-cholesterol. There was no formation of steratrienes from these compounds, but dihydroxycholesterol underwent considerable decomposition and alpha-epoxycholesterol underwent ring opening with formation of the dihydroxy derivative, whereas 7-ketocholesterol was rather stable
测定了用于精炼而非直接食用的粗制植物油样本中的植物甾醇氧化产物含量，这些植物油包括花生油、葵花籽油、玉米油、棕榈仁油和粗橄榄油。β-谷甾醇、豆甾醇和菜油甾醇的7α-和7β-羟基衍生物以及7-酮-β-谷甾醇是在几乎所有分析的油中发现的主要植物甾醇氧化物。在一些油中，还发现了β-谷甾醇的环氧和二羟基衍生物，但其含量极低。植物甾醇氧化物的最高总浓度分别在葵花籽油和玉米油中被发现，范围为4.5至67.5 ppm和4.1至60.1 ppm。花生油中的浓度较低，为2.7 - 9.6 ppm，棕榈仁油中的浓度为5.5 ppm，而在粗橄榄油中，六个分析样本中只有三个含有低浓度（1.5 - 2.5 ppm）的氧化植物甾醇。在棕榈油和椰子油样本中未检测到植物甾醇氧化物。对一个葵花籽油样本在80℃下用1%和2%的酸性白土和中性白土进行了1小时的脱色实验。脱色导致羟基植物甾醇减少，部分形成了在环系统的2-、4-和6-位带有三个双键的甾体烃（甾三烯）。同样的葵花籽油在180℃真空下脱臭1小时，未形成脱水产物，羟基植物甾醇完全回收。还用添加了7-酮胆固醇、二羟基胆固醇和α-环氧胆固醇的特级初榨橄榄油进行了酸性白土脱色试验。这些化合物没有形成甾三烯，但二羟基胆固醇发生了相当程度的分解，α-环氧胆固醇发生了开环反应并形成了二羟基衍生物，而7-酮胆固醇则相当稳定。
