Lecithins turbidity

Without an artificial sink, the membrane retentions are very high, with many basic probe molecules showing R > 80%. With the imposed sink, many of the retentions dropped by as much as 50%. Furthermore, just 0.5% wt/vol cholesterol in dodecane (in addition to the sink) caused increased retention to drop by at least a further 10-30%. It was not possible to form stable cholesterol-containing lipid models under sink conditions with Avanti s egg lecithin acceptor buffer solutions turned significantly turbid in the untenable model 13.1. 

Figure 4. Effect of salts on the formation of coacervates from lecithin and carrageen. The percentage of turbidity corresponds to the amount of coacervate (1).

Sample preparation followed the method described by Ryoto (13). One gram SPE or dry deoiled lecithin was dissolved in 100 g of oil and heated to 60-80°C for complete dispersion of the emulsifier. Ethanol-insoluble lecithin was added at a level of 1 mg/100 g oil and any residual to the ethanol was removed by heating a water bath. Samples with 0.5 and 0.25% SPE or dry lecithin were prepared by diluting the original sample with oil. Deoiling and fractionation of lecithin were done with acetone and ethanol, respectively, as reported by Ziegelitz (15). Turbidity test was conducted on 70 mL oil in a 100-mL tube at different concentrations of DK F-10 (0.0,0.5, and 1.0%) at several temperatures. 

Lecithins are complex phospholipids and occur in serum and egg yolk. Enzyme activity breaks down the emulsion and liberates free fats so that turbidity is created. The test is used for distinguishing Clostridium species and may be carried out using commercially available egg yolk suspensions. 

Egg lecithin sol gave with 6—1 a slight turbidity only very slowly and only in the neighbourhood of the reversal of charge point, therefore in the Fig. symbol 5—1 has been chosen for its flocculability. 

Nevertheless the affinity of Ca for the phosphate group of the lecithin is still appreciably greater than for the carboxyl group of the pectate (c ) 6). Formation of a tricomplex system is therefore still possible but this manifests itself only in an intensification of the turbidity, in the presence of lecithin. 

Here also Ca with nucleate results in the separation of a dicomplex system but this turbidity is hardly, or not at all, intensified in the presence of lecithin. This is also not surprising since b is no longer greater than c indeed the nucleate and the lecithin have now the same ionised group (phosphate group). 

Phosphaddylchotine-slerol acyitransferase (EC 2.3.1.43). Plasma cholesterol and triacylglycerols increased. Lysophosphatidylcholine and cholesterol esters decreased. Turbid or milky plasma. Multiple lipoprotein abnormalities. Comeal opacities. Normochromic anemia and proteinuria, due to renal damage. Therapy by enzyme replacement. [The enzyme catalyses formation of cholesterol esters by tranter of an unsaturated fatty acid from position 2 of lecithin to the 3-OH of cholesterol]... 

Fig. 2. A typical example of gel-filtration of liposomes coated with FITC(0.54)-OPP-50(1.8) from the free FITC-OPP developed with 200 mM Tris-HCl (pH 8.0) as an eluant. Liposomes were detected by turbidity at 220 nm (— —) and fluorescence intensity of FITC moiety at 520 nm (—O —) Coating with the polysaccharide was perfomed by incubating 3.0 ml of a sonicated liposome suspension prepared from 30 mg of egg lecithin with 1 ml of 200 mM Tris-HCl containing 5 mg of the FITC-OPP at 25 C (see text).

In an effort to determine as well as predict the formation of a sediment in canola oil, a method was developed based on solvent precipitation. Our studies indicated that the addition of 30-40% acetone addition to canola accelerated crystallization of the sediment (Liu et al 1996c). The relationship between turbidity and sediment formation in canola oil was shown to be non-linear. As can be seen in Figure 1.5, the presence of phospholipids also influenced turbidity as the addition of 2% lecithin increased turbidity by 23%. A review of this work can be found by Liu etal. (1998). 

FIGURE 1.5 Turbidity of canola oil containing 50 ppm of sediment as a function of cooUng time at 0°C. The turbidity for corresponding oils with 2% lecithin was also shown in broken line. (From Lin, H., Przybylski, R. and Eskin, N.A.M. 1996b. J. Am. Oil Chem. Soc. 73 1137-1141. With permission.)... 

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