W. De Greyt

Gas chromatographic characterization of vegetable oil deodorization distillate

Because of its complex nature, the analysis of deodorizer distillate is a challenging problem. Deodorizer distillate obtained from the deodorization process of vegetable oils consists of many components including free fatty acids, tocopherols, sterols, squalene and neutral oil. A gas chromatographic method for the analysis of deodorizer distillate without saponification of the sample is described. After a concise sample preparation including derivatization and silylation, distillate samples were injected on column at 60 degrees C followed by a gradual increase of the oven temperature towards 340 degrees C. The temperature profile of the oven was optimized in order to obtain a baseline separation of the different distillate components including free fatty acids, tocopherols, sterols, squalene and neutral oil. Good recoveries for delta-tocopherol, alpha-tocopherol, stigmasterol and cholesteryl palmitate of 97, 94.4, 95.6 and 92%, respectively were obtained. Repeatability of the described gas chromatographic method was evaluated by analyzing five replicates of a soybean distillate. Tocopherols and sterols had low relative standard deviations ranging between 1.67 and 2.25%. Squalene, mono- and diacylglycerides had higher relative standard deviations ranging between 3.33 and 4.12%. Several industrial deodorizer distillates obtained from chemical and physical refining of corn, canola, sunflower and soybean have been analyzed for their composition.

Fat absorption and metabolism in bile duct ligated rats.

Background: Bile excretion is obstructed in children with extrahepatic bile duct atresia (EHBA) resulting in fat malabsorption and disturbed lipid metabolism. Aim: Investigate if the bile duct ligated rat exhibits similar deviations as patients with EHBA under different feeding conditions. Methods: 6 bile duct ligated Wistar rats and 12 matched paired controls were randomised over 3 feeding groups. Rats were killed 16 or 30 days postsurgery. Faeces, blood and livers were collected. Fat absorption was evaluated, markers for cholestasis and the fatty acid composition of serum phospholipids (PL) and cholesterol esters (CE) were determined. Fatty acid desaturation activities in liver microsomes were measured. Results: Cholestatic bile duct ligated rats have a lower fat absorption coefficient and a lower fraction of 18:2n–6 and 18:3n–3 in serum triglycerides than their controls. This demonstrates that bile duct ligated rats suffer from fat malabsorption. In contrast to the observations in serum triglycerides, 18:2n–6 and 18:3n–3 were not reduced in serum PL and CE of cholestatic rats. Overflow of 18:2n–6 rich biliary PL in the general circulation could contribute to this observation. In agreement with what was found in man, serum PL of cholestatic rats have a higher 16:0/18:0 ratio, increased monoenes and reduced unsaturated fatty acids. However, no differences were observed in microsomal desaturation activities. Conclusion: Cholestatic bile duct ligated rats exhibit similar deviations in serum fatty acid composition as found in patients with EHBA, therefore they can be used as a model for this human disease.

Comparison of steradiene analysis between GC and HPLC

Steradienes are sterol dehydration products formed in the vegetable oil refining process during the bleaching and deodorization process. The 3,5-stigmastadiene content of vegetable oils was quantified by GC as well as by HPLC. A good repeatability, as indicated by the low relative standard deviation of 1.11 and 2.46%, and accuracy levels of 113.9 and 107.7% were obtained for the GC and HPLC analytical method respectively. Although a good comparison between both analytical methods was observed, GC data consistently gave on average a higher 3,5-stigmastadiene content of 19.6% compared to HPLC data. Probably there is an overestimation of the steradiene content analyzed by GC due to peak overlap with other hydrocarbons as the FID detector is not as selective compared to the UV detector applied in the HPLC analysis.

Cholesterol oxidation in tallow during processing

Abstract The oxidation of cholesterol during the bleaching and deodorization process of tallow was studied. Eight polar cholesterol oxidation products were targeted, but only cholest-5-en-3β,7β-diol (7β-HC) and 5β, 6β-epoxy-5β-cholestan-3β-ol (β-CE) could be quantified in the samples analysed. The content of 7β-HC was slightly higher in the processed tallow (0.6–0.7 μg/g) compared with natural tallow (0.2 μg/g). However, the content of β-CE was considerably increased during processing, ranging from 0.8 to 3.4 μg/g, compared with 0.6 μg/g in the natural tallow. The general observation was that the content of β-CE was influenced by temperature, duration and type of bleaching earth.