Degree Type

Thesis

Date of Award

2009

Degree Name

Master of Science

Department

Food Science and Human Nutrition

First Advisor

Tong Wang

Abstract

High-purity oleate esters can decrease the melting points and improve the oxidative stability of lubricants. High-oleic soybean oil (HOSO) was esterified to butyl or isopropyl esters. Fractional distillation and low-temperature crystallization were applied to improve the purity of oleate of HOSO esters. Although the purity of butyl esters of HOSO attained 91.8% by fractional distillation, the rate of distillation must be slow which made this approach not very feasible. After subjecting the esters to a two-step crystallization at reduced temperatures, the percentage of oleate in the HOSO esters was increased from 83.2 to 92.5%. The percentage of saturated fatty acids decreased to less than 2.2%, but polyunsaturates percentage remained almost unchanged.

Methyl linoleate monolayer has a highest lipid oxidation rate. It can be employed to produce useful oxidation products including expoxides and hydroxides. Methyl linoleate (20% by weight) was coated to silica gel H to form monolayers and heated at 35, 40, 50 and 60yC. Methyl palmitate (5% by weight of methyl linoleate) was added as internal standard. The identification of oxidation products was by comparison to standards. The oxidation rate increased with temperature. The temperature for optimal yields of epoxides (20.26%) and total non-scission products (NSPs, 38.79%) was 50yC. Citric acid and EDTA (0.01% and 0.02% by weight of oil) were added as chelating agents to minimize the effects of iron on oxidation. Citric acid at 0.01% achieved higher PV and also reduced the loss of NSPs to scission products (SPs) after reaching the maximum peroxide value. The addition of 20 ppm vanadium (by weight of silica gel) increased the yield of epoxides (23.85%); however, it also led to lower peroxide values and longer induction period.

After long operation of biodiesel engine, hard and dark deposits accumulate on injector tips, which affect engine performance. The type and composition of biodiesel have major effect on the formation of deposits. The major compounds of thermal stable residues of biodiesel from muffle furnace heated at 200yC for 15 min were analysed by GC-MS. Those compounds were mostly fragments of fatty esters, in which the terminal ends are acids, aldehydes. Methyl linolenate formed significantly greater amounts of residue than neat biodiesel, methyl palmitate, methyl stearate, methyl oleate, and methyl linoleate. The GC profile of methyl linolenate residues included more compounds than from other oils.

Copyright Owner

Haixia Liu

Language

en

Date Available

2012-04-30

File Format

application/pdf

File Size

50 pages

Included in

Nutrition Commons

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