Crystallization of oils

Povey, M.J.W. 2001. Crystallization of oil-in-water emulsions. In Crystallization Processes in Fats and Fipid Systems (K Sato, N. Garti, eds.), pp. 255-288, Marcel Dekker, New York. 

Blaurock, A.E. 2000. Fundamental understanding of the crystallization of oils and fats. In Physical Properties of Fats, Oils and Emulsifiers (N. Widlak, ed.), AOCS Press, Champaign. 

When it comes to predicting the point of crystallization, it gets more complicated. Crystallization of oils or fats or of FAME is a thermodynamic process. FAME crystallization by itself is probably much simpler than the complex crystallization of oils and fats as seen in food products from chocolate to margarine. Basic research on FAME crystallization is in progress, but currently not readily available to put in a simple and useful mathematical model sufficient to describe the CP, PP, or CFPP. 

The Avrami equation (1), originally developed for the crystallization of metals from melt, has been applied by many researchers to the crystallization of oils and fats in order to elucidate information on their crystallization mechanism. The Avrami equation is based on the model of a growing sphere crystallizing from a melt of uniform density without impingement. The usual Avrami exponent, used to draw conclusions with respect to the crystallization mechanism of the system, is observed to be about three or four for oils and fats after rounding off to whole integers. 

In addition, the original equation developed was based on a model where the crystal growth is over a solid sphere. In the case of the so-called three-dimensional spheres assumed by the (3 and 3 crystals of oils and fats, it can be seen from the electron microscope pictures (12) that the spheres are not solid but contain a lot of empty spaces or voids. 

The caution by Marangoni (8) on the misuse of a modified form of the Avrami equation is rightly justified within the context of the warning. However, if the equation is to be applied to the crystallization of oils and fats in order to elucidate information on the mechanisms of their nucleation and growth, the equation will have to be modified to suit the conditions prevailing in the system. 

Solid lipid microcarriers W/O microcarrier S/O microcarrier Solid microcarrier Crystallization of oil phase from W/OAV emulsion Freeze-drying of S/OAV emulsion Freeze-drying of W/OAV emulsion Shimizu et al. (2002a), Nakashima (2002) Shimizu (2002a), Nakashima (2002) Kukizaki et al. (2001)... 

The pour point is the lowest temperature at which an oil can still pour while it is cooled, without agitation, under standardized conditions. The pour point of paraffinic bases is linked to the crystallization of n-paraffins. The pour point of naphthenic bases is related to a significant viscosity increase at low temperatures. This property can be improved by additives. 

Disconnect the column, and remove the flask from the oil-bath. Add 25 ml. of dilute hydrochloric acid to the flask, shake the contents vigorously, and chill in ice-water, when crystals of benzhydrol will separate. (Occasionally the hydrol will separate initially as an oil, which ciystallises on vigorous stirring.)... 

Method 2. Equip a 1 htre thre necked flask with a double surface reflux condenser, a mechanical stirrer and a separatory funnel, and place 12 -2 g. of dry magnesium turnings, a crystal of iodine, 50 ml. of sodium-dried ether and 7-5 g. (5 ml.) of a-bromonaphthalene (Section IV,20) in the flask. If the reaction does not start immediately, reflux gently on a water bath until it does remove the water bath. Stir the mixture, and add a solution of 96 g. (65 ml.) of a-bromonaphthalene in 250 ml. of anhydrous ether from the separatory funnel at such a rate that the reaction is vmder control (1 -5-2 hours). Place a water bath under the flask and continue the stirring and refluxing for a further 30 minutes. The Grignard reagent collects as a heavy oil in the bottom of the flask ... 

Diethylbarbituric acid. In a dry 250 ml. distilling flask, fitted with a thermometer reaching to within 3-4 cm. of the bottom and a condenser, place 51 g. of clean sodium and add 110 g. (140 ml.) of super-dr ethyl alcohol (Section 11,47,5). When all the sodium has reacted, introduce 20 g. of ethyl diethylmalonate and 7 0 g. of dry imea (dried at 60 for 4 hours). Heat the flask in an oil bath and slowly distil off the ethyl alcohol. As soon as the temperature of the liquid reaches 110-115°, adjust the flame beneath the bath so that the contents of the flask are maintained at this temperature for at least 4 hours. Allow the flask to cool somewhat, add 100 ml. of water and warm until the solid (veronal-sodium) dissolves. Pour the solution into a beaker, and add a further 100 ml. of water but containing 7 0 ml. of concentrated siilplmric acid this will hberate the veronal from the sodium derivative. The veronal usually crystallises out if it does not, add a few more drops of dilute sulphuric acid until the solution is acid to Congo red. Heat the contents of the beaker, with stirring and the addition of more water if necessary, until all the veronal dissolves at the boiling point. Allow the hot solution to cool, filter off the crystals of veronal and diy in the air. The yield is 12 g., m.p. 190°. 

The soiution is aliowed to cool and the crystals of the P2P-bisulfite addition compound are then separated by vacuum filtration, washed with a little clean dH20 then washed with a couple hundred mLs of ether, DCM or benzene. The filter cake of MD-P2P-bisulfate is processed by scraping the crystals into a flask and then 300mL of either 20% sodium carbonate solution or 10% HCi soiution are added (HCI works best). The soiution is stirred for another 30 minutes during which time the MD-P2P-bisulfite complex will be busted up and the P2P will return to its happy oil form. The P2P is then taken up with ether, dried and removed of the solvent to give pure MD-P2P. Whaddya think of that ... 

D. Now the ether will be a deep reddish yellow. Distill off the ether...quack...and take the temp up to 170 C to drive off any other volatiles. Should recover 90%+ of the original weight of oil. Now add 500 ml of saturated bisulfite and stir for 1.5 hours...Quack Vacuum Filter, the duck fat crystals Wash with water and ether, yield dull fine ppt in the filter cake...stable bisulfite addition product...can be stored forever...QuackU Yield -50 to 80% depending on a ducks technique ... 

A 25% dispersion of NaH crystals ia oil is obtained. The commercial product, after filtration, is a 60% dispersion of NaH crystals (5—50 p.m). The oil dispersions can be handled quite safely because the oil phase provides a barrier to air and moisture, whereas the unprotected crystals react vigorously. Traces of unreacted sodium metal give the product a gray color. 

The more modem processes adopted in the United Kingdom and some European plants (20) are also based on crystallization of the primary naphthalene oil, which is diluted with lower crystallizing material to give a feedstock crystallizing point at 55°C. This material is cooled in closed, stirred... 

The detection of Hquid crystal is based primarily on anisotropic optical properties. This means that a sample of this phase looks radiant when viewed against a light source placed between crossed polarizers. An isotropic solution is black under such conditions (Fig. 12). Optical microscopy may also detect the Hquid crystal in an emulsion. The Hquid crystal is conspicuous from its radiance in polarized light (Fig. 13). The stmcture of the Hquid crystalline phase is also most easily identified by optical microscopy. Lamellar Hquid crystals have a pattern of oil streaks and Maltese crosses (Fig. 14a), whereas ones with hexagonal arrays of cylinders give a different optical pattern (Fig. 14b). 

The crystallization of wax from lubricating oil fractions makes better oil. This is done by adding a solvent (often a mixture of benzene and methyl ethyl ketone) to the oil at a temperature of about -5 F. The benzene keeps the oil in solution and maintains fluidity at low temperature the methyl ethyl ketone acts to precipitate the wax. Rotary filters deposit the wax crystals on a sp woven cloth stretched over a perforated cylindrical drum. A vacuum in the drum draws the oil through the perforations. The wax crystals are removed from the cloth by metal scrapers and ol vent-washed to remove oil followed by solvent distillation to remove oil for reuse. 

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