SEPARATION OF STEROLS FROM DEODORIZER DISTILLATE BY CRYSTALLIZATION

Separation of sterols from deodorizer distillate (DOD) by crystallization without pretreatment was investigated. DOD was dissolved in different solvents and crystallization was then conducted at-10 or-20C, with a solvent-to-DOD ratio of 3:1 (v/w). Several solvents such as methanol, acetone, and their mixtures, were examined for their separation effectiveness. The sterol crystals formed were removed from the solution by centrifugation at low temperature and subsequent filtration. The best results were obtained by crystallization at -20C for 24 h with a mixture of acetone and methanol, followed by centrifugation, filtration and washing steps. Over 90% of the original tocopherols and squalene in DOD were recovered in the filtrate fraction, while 80% of total sterols in DOD were retained in the cake fraction.     

LAGRANGE MULTIPLIERS FOR THE INTERMEDIATE METALLIC REGIONS IN THE COMPUTATION OF THE POTENTIAL DISTRIBUTION OF INSULATOR CHAINS BY FEM

ABSTRACT

It is very important to predict the behaviour of the high voltage insulators at the operating conditions from the point of improving of the design and practical selection of the insulator type. Therefore, it is necessary to compute the potential and electric field distributions and to determine the critical regions forced much more by the electric field. In case the insulator surface is clean or the pollution film at the surface is dry, a little capacitive current flows and the solution of the problem results in a capacitive potential distribution.

In the numerical computational methods of potential distribution of insulator chains, it requires to insert into the resulting equation system as boundary conditions of the intermediate metallic zones that connect two units that have the same potential at every point. In this work, the potential distribution of clean insulator chains have been computed using the Finite Element Method (FEM). The metallic zones between the units have been taken into account as equipotential surfaces by Lagrange Multipliers. The computed results were compared with experimental results obtained by using the Conducting Paper Method and good agreement was observed.     

PREPARATION OF TOCOPHEROL SUCCINATES FROM DEODORIZER DISTILLATE

Preparation of tocopherol succinates from deodorizer distillate (DOD) with or without pretreatment was studied. To reduce damage to tocopherols, the reaction mixture was purged with nitrogen during heating. For DOD as a raw material, the succinylation procedure for converting tocopherols to tocopherol succinates was optimized in terms of type of catalyst, reaction time, and reaction temperature. Potassium acetate performed best among the catalysts tested. Using potassium acetate, 90% conversion was achieved within 30 min for total tocopherols and within 90 min for α-tocopherol. The optimal reaction time ranged from 60 to 90 min. To obtain rapid reaction and high conversion, the suitable temperature range was 100–140C. Under optimal conditions, a conversion of 93% was reached. For sterol-removed DOD as a raw material, the succinylation reaction was carried out at 140C for 1 h using potassium acetate as a catalyst. When using 10% of succinic anhydride and 1.3% of catalyst, over 80% of total tocopherols were converted to tocopherol succinates with conversion of α-tocopherol being highest among all isomers (over 90%). The conversion was significantly increased to over 90% by increasing the amount of succinic anhydride from 10 to 13% and that of the catalyst from 1.3 to 2%. Meanwhile, the free fatty acid (FFA) content was increased to approximately 10% after the succinylation reaction.     

ANTIOXIDANT ACTIVITIES OF ENDEMIC SIDERITIS LEPTOCLADA AND MENTHA DUMETORUM AQUEOUS EXTRACTS USED IN TURKEY FOLK MEDICINE

Total phenolic contents, hydroxyl radicals and one 1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activities, antioxidant capacities and reducing powers of Sideritis leptoclada, which is an endemic plant to Turkey, and Mentha × dumetorum were investigated in water extracts. Total phenolic contents were detected to be 0.32 µg gallic acid/µg dry biomass in the presence of 1.33 and 9.82 µg/mL, respectively. Fifty percent scavenging activities of hydroxyl and DPPH radical were determined with 0.03 and 0.16 mg/mL extracts of S. leptoclada and 0.21 and 1.6 mg/mL extracts of Mxdumetorum. In addition, total antioxidant capacities of S. leptoplada were also higher than Mxdumetorum and there was a significant difference between the controls. The result of this study suggests that extracts of S. leptoclada and Mxdumetorum can be used as potential source of natural antioxidants and as a possible food supplement or in the pharmaceutical industry.

PRACTICAL APPLICATIONS

The research is focused on the determination of new potential plant sources of antioxidants that can be used as food. Antioxidants are vital substances that possess the ability to protect the body from damage caused by reactive oxygen species induced oxidative stress. In this study, infusions in boiled water of Sideritis leptoclada , which is a plant endemic to Turkey, and Mentha x dumetorum have high levels of antioxidant capacity. The results of the study show that extracts of S. leptoclada and Mxdumetorum can be used as a supplement agent to increase in quality of food and for the pharmaceutical industry.     

MISCELLA REFINING OF ISOPROPANOL EXTRACTED COTTONSEED OIL

A technologically feasible cottonseed oil-isopropyl alcohol (IPA) miscella refining process was developed to produce Prime Bleachable Summer Yellow (PBSY) quality cottonseed oil. Individual steps necessary to refine cottonseed oil-IPA miscella were determined and improved. The miscella was first neutralized with 20 Baume (Be') caustic solution (50% excess) using a homogenizer. After centrifugation to remove soapstock, the two remaining liquid layers were separated and desolventized. The refined oils from bottom and top layers were then water washed using 12.5 and 20% hot water (w/w), respectively. Water washing efficiently recovered the oil from the top miscella layer and reduced soap and phosphorus contents. The water washed and dried oil from the bottom and top layers were treated with 0.5 and 4% (w/w) acid-activated bleaching clay, respectively. Good quality bleached oil was then obtained. However, the quality of bleached oil produced from the bottom layer was better than that of the top layer. Comparative experiments with both IPA and hexane miscellas showed that quality of the refined oil from cottonseed oil-IPA miscella is as good as that produced from the cottonseed oil-hexane miscella using the process developed in this study.     

MODELING OF SELECTIVE EXTRACTION OF PHOSPHATIDYLCHOLINE FROM A COMPLEX LECITHIN MIXTURE USING SUPERCRITICAL CO2/ETHANOL

Phospholipids are not soluble in pure carbon dioxide used in supercritical flucid extraction due to their nonpolar nature. However, addition of ethanol as an entrainer makes it possible to selectively extract phoshatidylcholine (PC) from a phospholipid mixture. Phosphatidylcholine has a potential value in the pharmaceutical industry. In this study, two different models to predict the extraction behavior of phospholipids (a multicomponent system) with an entrained supercritical fluid (carbon dioxide/ethanol) were evaluated. The models developed for selective extraction of PC from a complex lecithin mixture were a mixed-flow model with an overall mass transfer coefficient as well as a shrinking-core model. Both models gave similar results in predicting the experimental data due to two main reasons: (1) shrinking-core model was developed with the perfect mixing assumption of the fluid phase, and (2) extraction of phospholipids from the lecithin mixture with SC-CO₂/ethanol was a slow process.     

SEPARATION OF TOCOPHEROL SUCCINATES FROM DEODORIZER DISTILLATE

Isolation of tocopherol succinates from sterol-removed, succinated deodorizer distillate (DOD) mixture by crystallization was investigated. Membrane technology was also evaluated for its effectiveness to separate tocopherol succinates from mixtures containing sterols and tocopherols. Crystallization was conducted at −20C for 24 h with different solvents, including hexane, petroleum ether, and a mixture of acetone and methanol (4:1, v/v). The crystallization results showed that recovery of tocopherol succinates from the cake fraction was poor with all solvents tested, with less than 10% of original tocopherol succinates in the raw material being crystallized under conditions employed. Among the solvents tested, hexane was better for the recovery of non-α-tocopherol succinates in the cake fraction. Furthermore, a high properties of free fatty acids (FFA) was co-crystallized along with tocopherol succinates for all solvents used, leading to tocopherol succinates contents in the cake fractions lower than that in the raw material. Two nanofiltration membranes (DS-7 and AP01) were also examined using hexane or petroleum ether as a solvent. The recovery of tocopherol succinates was over 60%. However, their concentration was increased only by 6%. A combined process was then evaluated that included crystallization before succinylation, succinylation, first stage membrane separation, and second stage membrane separation. The final tocopherols concentration derived from this combined process was mice as much as that of the original DOD.     

The effect of a sliding load on strain gauges embedded under the contact surface

Strain gauges embedded in plastic models can be used in three dimensional stress analysis. When gauges are located immediately below a surface subjected to the tangential traction of a sliding load, unexpected values are recorded. This phenomenon was investigated by suitably loading a semi–infinite solid with normal and shear stresses and comparing theoretical strain values with the experimental results. The comparison showed that strain gauges embedded in epoxy can be successfully used under sliding loads provided that the gauge depth below the contact surface is greater than a critical value.