Neutralization is an important step in the chemical refining of edible oils. Free fatty acids (FFA) are generally removed in neutralization as sodium soaps but neutral oil is also entrapped in the emulsion and removed with the soap during centrifugation. Thus, alkali neutralization causes a major loss of neutral oil in the chemical refining of edible oils. The effects of demulsifiers (NaCl, KCl, Na 2 SO 4 and tannic acid) on reducing alkali refining losses of refined palm, soybean, and sunflower oils (used as model oils) incorporated with FFA from rice bran oil were investigated. Adding small amounts of demulsifiers to the alkali neutralization step significantly reduced neutral oil loss of these model oils. All demulsifiers except for tannic acid had similar effects on refining losses in all oil model systems. The optimum demulsifier content was 1.0 % (w/w of oil).
Rice bran wax (RBW) is a by product of rice bran oil refinery. Crude RBW from refineries in Thailand had only 20-40% of the wax ester. The major impurity was triglyceride (TG). Purification of RBW requires a rapid and reliable method of analysis. In this study, a modified size exclusion HPLC column (100-Å Phenogel) was reported. Degree swellings of the gel matrix were controlled by isooctane-toluene mobile phase ratio. With pure toluene as the mobile phase, the gel matrix is fully swollen. Wax and TG could not be separated. With 65:35 (v/v) of isooctanetoluene, wax and TG as well as other lipids were baseline separated. The resolution (Rs) between wax and TG was greater than 1.5. Acetic acid (0.1% or higher) in the mobile phase could suppress peak tailing and improved separation of the lipid containing active hydroxyl groups such as free fatty acid, diglyceride and monoglyceride without affecting retention times of the wax and the TG. Separation of lipids in crude RBW could be completed in a single run on the modified Phenogel column (100 Å ) with the total analysis time less than 15 min. The relationship between the amount of wax in the sample and the peak area was linear with the R 2 greater than 0.98.
The effect of π-electrons and hydroxyl group on the separations of vitamin E on a swelling-controlled polystyrene-divinylbenzene (Phenogel) column using toluene/isooctane as the mobile phase was investigated. The effect of the π-electrons was demonstrated in the baseline separation of α-tocopherol and α-tocotrienol on a 100-Å Phenogel column. In addition, baseline separation of α-, (β- + γ-)- and δ-tocopherol could be achieved on this column. The separation mechanism of these isomers are due to the difference in the interactions between the hydroxyl group on the chromanol ring of each tocopherol and the gel matrix caused by the steric hindrance of methyl group(s). It was concluded that solutes of the same molecular size but different in the polar groups could be separated on a high performance size-exclusion chromatography by controlling the swelling of the gel matrix via modification of the mobile phase.
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