Rice bran (Oryza sativa) oil is known for containing higher amount of free fatty acid (FFA) generated by hydrolytic enzyme. This FFA causes heavy neutral oil losses due to saponification and emulsification since it produces large amount of soap in the conventional alkali refining process. In the present study the FFA of degummed rice bran oil (RBO) was significantly reduced by reesterifying it with glycerol. The reesterification process was carried out by varying the temperature and amount of excess glycerol using 0.2% catalyst (SnCl2). The maximum efficiency of the process could be attained at 200°C using 70% excess glycerol and the maximum reduction in acid value (from 24.3 to 3.0) of RBO was observed within 4 h. The reesterified RBO was used to prepare stand oil and varnish and their performance characteristics were compared with those of the products obtained from dehydrated castor oil (DCO).
An attempt was made to study the bleaching ability of some alternative adsorbents like rice husk ash (HC), acid activated rice husk ash (AC), rice husk silica (S), and Al(OH)3 gel to replace commercial Acid Activated Clay (AAC, like Tonsil Earth: TE) for bleaching of mustard oil. Quantities of AAC used were varied from 0.5 to 2.0 % (w/w). It was used as such and along with commercial activated carbon (0.25-0.75 %, w/w), and laboratory prepared Al(OH)3 gel, rice husk ash and silica isolated from husk. The results show that quantity of AAC to be used can be reduced to 1.00 to 1.25% (w/w) by using a combination of AAC along with rice husk ash; Al(OH)3 gel; rice husk silica either by wet bleaching or by conventional bleaching method.
In this study, the effect of a random copolymer of polyoxyethylene (POE, 38 mol) / polyoxypropylene (POP, 10 mol) pentaerythrytol tetramethyl ether [PEPTME (38/10)], which is unable to form a self-organizing structure on account of its bulkiness, on the microemulsion phase was examined. The phase diagram of the liquid paraffin - nonionic surfactant+PEPTME (38/10) - water system was compared with that of polyoxyethylene (POE) / polyoxypropylene (POP) dimethyl ether (EPDME) system which has a straight-chain structure. In the previous study, the authors reported that a special droplet type microemulsion (highly concentrated microemulsion) was formed, when EPDME was distributed in the hydrophilic moiety of a surfactant in a lamellar liquid crystalline phase. In contrast, it was found that the use of PEPTME (38/10) resulted in disappearance of lamellar as well as hexagonal and cubic liquid crystals, and the formation of an optically isotropic and fluid phase owing to the relationship between the original microemulsion phase and the highly concentrated microemulsion phase. Thus, PEPTME (38/10) was considered to be most suited for preparing highly concentrated microemulsions.
A water/supercritical CO2 microemulsion (W/scCO2 μE) with methyl orange (MO) and sodium bis(1H,1H,2H,2H-heptadecafluorodecyl)-2-sulfosuccinate, 8FS(EO)2, was characterized by means of UV-visible absorption spectral and dynamic light scattering (DLS) measurements. Visual observation of the scCO2 mixtures revealed transparent and reddish scCO2 phases with and without separated excess water; they were identified as Winsor-II and Winsor-IV W/scCO2 μE, respectively. The polarities of the aqueous cores in the Winsor-IV W/scCO2 μE were examined by observing the spectral shift of the absorbance maximum of MO. It was observed that with an increase in the water-to-surfactant molar ratio (W0c), the measured absorbance maximum shifted from 418 to 423 nm, which suggests that the polarity of the environment surrounding the MO molecules was methanol-like, and the polarity increased with W0c. The hydrodynamic diameter of Winsor-IV W/scCO2 μE increased drastically with W0c but gradually with a decrease in the CO2 density. The increase in the diameter was a result of the aggregation of the μE droplets and the fusion promoted by the increase in W0c and the decrease in the CO2 density, in addition to the swelling of reversed micelles.
Emulsions consisting of n-alkane/water using α, β, and γ-cyclodextrin (α, β, and γ-CD) as an emulsifier were prepared and characterized by means of several physicochemical techniques. A phase diagram of the n-alkane/CD/water system showed that an oil in water (O/W) emulsion can be prepared from a mixture of the appropriate composition. The dissolved n-alkane/CD complexes formed at low CD concentrations showed surface-activity, but emulsions could not be prepared from these complexes. On the other hand, the precipitated complexes formed at high CD concentrations when adsorbed to the oil/water interface, and served as an emulsifier for formation of emulsions. These results showed that the emulsions formed were of the Pickering emulsion. In addition emulsion formation was governed by the wettability and the surface free energy of the precipitated complexes.
Kluyveromyces lactis strain M-16 isolated from raw milk accumulates a high amount of steryl glucoside in the cells. Under high temperature or in the presence of NaCl, this strain did not show better growth than other K. lactis strains that hardly accumulated steryl glucoside. Heat shock elevated the content of steryl glucoside 3.2-fold, which accounted for 27% of the total sterol lipids, and simultaneously reduced that of acyl sterol. Both strains, M-16 and NBRC 1267, contained ergosterol as a principal component, and dihydroergosterol was also included in steryl glucoside of strain M-16. Lanosterol was a major component second to ergosterol in free sterols. In acyl sterol of strain M-16, the proportion of 4,4-dimethylzymosterol was higher than that of ergosterol. Excess synthesis of steryl glucoside in strain M-16 consumes ergosterol and dihydroergosterol in the pool of free sterols, and acyl sterol may inevitably take in 4,4-dimethylzymosterol and 4-methylfecosterol, the intermediates in the biosynthetic pathway to ergosterol, as a component sterol.
Succinoyl trehalose lipids (STLs) are promising glycolipid biosurfactants produced from n-alkanes by Rhodococcus sp. These compounds show not only unique interfacial properties but also versatile biochemical actions. In this study, we determined for the first time the complete structure of the main component, namely STL-1, based on NMR, MALDI-TOF/MS and GC-MS analyses. The present STL-1 produced from n-hexadecane was identified as 3,4-di-O-alkanoyl-2-O-succinoyl-α-D-glucopyranosyl-2′-O-succinoyl-α-D-glucopyranoside. The major fatty acid of STL-1 was C16, indicating that n-hexadecane as the carbon source is directly incorporated into the carbohydrate moiety via terminal oxidation. We also investigated its surface active properties using a Whilhelmy method at 25°C. The estimated CMC and γCMC values for STL-1 were 5.6×10-6 M and 19.0 mN/m, and those for sodium salt (NaSTL-1) were 7.7×10-6 M and 23.7 mN/m, respectively. The high activity of STL-1 was probably due to the unique molecular structure resulting from its multiple functional groups including succinic acids and two long fatty acids. Accordingly, STL-1 and its sodium salt were demonstrated to exhibit an excellent surface-activity at remarkably low concentrations, and should have great potential for environmentally friendly surfactants.