Fractionation lecithin

There are six common grades of lecithin available including commercially available. Besides these common commercial grades, more special products are available, e g., enzymatically modified lecithin and phospholipids, semisynlhelic phospholipids, and acetylaled lecithins. 

The PC/PE ratios of alcohol-fractionated lecithins are largely determined by processing variables such as alcohol polarity, concentration, lecithin/alcohol ratio, temperature, and extraction time (33). By extracting natural lecithin with a PC to PE ratio of 1.2 1 with 90% ethanol, an alcohol-soluble fraction with a PC/PE ratio of 8 1 can be obtained (33, 120). The fractions may be blended with other surfactants or carriers to obtain desired functionality. 

Standard-grade (crude) lecithins are excellent water-in-oil emulsifiers. However, modified lecithins can function to emulsify either water-in-oU or oil-in-water emulsions, depending on the type of lecithin modification and the specific parameters of the system. These system parameters can include pH, types of components, component ratios, solids content, and others. Unlike crude lecithins, hydroxylated lecithins are stable in acid systems (pH 3.5). Fractionated lecithins can be manufactured for specific emulsion types. As lecithin s emulsifying activity is partially dependent on its phospholipid ratio, changing the ratio can alter its emulsifying capabilities (7). 

Solubilization. Most lecithins can aid in the production of microemulsions, an example being oil-soluble flavors in aqueous systems. Although standard-grade lecithins do not disperse in water, many modified or fractionated lecithins are water-dispersible, and they can be used to produce microemulsions. Standard-grade lecithin can be blended with other surfactants (e.g., ethoxylated monoglycerides) to produce synergistic emulsifier blends that are also effective in producing microemulsions. 

Common soy derivatives (Figure 8.2) are lecithin (raw, fractionated, phospha-tidylcholin fraction), tocopherols (vitamin E), soy isoflavones, soy flour, molasses, vegetable oil, and sterols. DNA can usually be found only in raw and some fractionated lecithins and soy flour as well as cmde soybean oil. 

Lysolecithins, which are more hydrophilic, show stronger oil-in-water emulsifying properties. Stable microemulsions have been prepared with various fractionated lecithins. These mlcroemulsions are used in direct applications as reservoirs for certain active materials (flavors, antioxidants, nutraceuticals, etc.) or as microreactors for enzymatic reactions. Several of these applications were... 

Purification Processes. Separation of neutral and polar Hpids, so-called deoiling, is the most important fractionation process in lecithin technology (Fig. 3). Lecithin is fluidized by adding 15—30% acetone under intensive agitation with acetone (fluidized lecithin acetone, 1 5) at 5°C. The mixture goes to a separator where it is agitated for 30 minutes. The agitator is then stopped and the lecithin separates. The oil micella is removed and the acetone evaporated. After condensation the acetone is returned into the process. 

To produce highly purified phosphatidylcholine there are two industrial processes batch and continuous. In the batch process for producing phosphatidylcholine fractions with 70—96% PC (Pig. 4) (14,15) deoiled lecithin is blended at 30°C with 30 wt % ethanol, 90 vol %, eventually in the presence of a solubiHzer (for example, mono-, di-, or triglycerides). The ethanol-insoluble fraction is separated and dried. The ethanol-soluble fraction is mixed with aluminum oxide 1 1 and stirred for approximately one hour. After separation, the phosphatidylcholine fraction is concentrated, dried, and packed. 

Pig. 4. Batch process for producing phosphatidylcholine fractions. 1, Ethanol storage tank 2, deoiled lecithin 3, solubiHzer 4, blender 5, film-type evaporator 6, ethanol-insoluble fraction 7, ethanol-soluble fraction 8, aluminum oxide 9, mixer 10, decanter 11, dryer 12, aluminum oxide removal 13, phosphatidylcholine solution 14, circulating evaporator 15, cooler 16, dryer and 17, phosphatidylcholine. 

In the continuous process for producing phosphatidylcholine fractions with 70—96% PC at a capacity of 600 t/yr (Pig. 5) (16), lecithin is continuously extracted with ethanol at 80°C. After separation the ethanol-insoluble fraction is separated. The ethanol-soluble fraction mns into a chromatography column and is eluted with ethanol at 100°C. The phosphatidylcholine solution is concentrated and dried. The pure phosphatidylcholine is separated as dry sticky material. This material can be granulated (17). 

Fig. 5. Continuous process for producing phosphatidylcholine. 1, Lecithin 2, ethanol 3, blender 4, diffuser 5, thin-type evaporator 6, ethanol-insoluble fraction 7, heat exchanger 8, chromatography column (Si02) 9, prestream 10 and 12, phosphatidylcholine solution 11, circulating evaporator 13, dryer ...

The standard methods (26) of analysis for commercial lecithin, as embodied in the Official and Tentative Methods of the American Oil Chemists Society (AOCS), generally are used in the technical evaluation of lecithin (27). Eor example, the AOCS Ja 4-46 method determines the acetone-insoluble matter under the conditions of the test, free from sand, meal, and other petroleum ether-insoluble material. The phosphoHpids are included in the acetone-insoluble fraction. The substances insoluble in hexane are determined by method AOCS Ja 3-87. 

The total phosphoms content of the sample is determined by method AOCS Ja 5-55. Analysis of phosphoUpid in lecithin concentrates (AOCS Ja 7-86) is performed by fractionation with two-dimensional thin-layer chromatography (tic) followed by acid digestion and reaction with molybdate to measure total phosphorous for each fraction at 310 nm. It is a semiquantitative method for PC, PE, PI, PA, LPC, and LPE. Method AOCS Ja 7b-91 is for the direct deterrnination of single phosphoHpids PE, PA, PI, PC in lecithin by high performance Hquid chromatography (hplc). The method is appHcable to oil-containing lecithins, deoiled lecithins, lecithin fractions, but not appHcable to lyso-PC and lyso-PE. 

Plant Protection. Lecithin (0.5—10%) and phosphohpid fractions ate used in fertilizers (qv), herbicides (qv), insecticides, and fungicides as emulsifiers or to increase the effectiveness of the active ingredient (45). In insecticides (0.5—5% lecithin), lecithin is used for improved emulsification, spreading, penetration, and adhesion (see Insectcontroltechnology). 

The chromatogram of the commercial soya lecithin as shown in Figure 4 suggests a number of components and all subsequent work was done with the ethanol-soluble fraction, i.e., phosphatidyl choline, or the ethanol-insoluble fraction, comprised primarily of other phosphatides. 

Figure 5. GPC chromatograms of phosphatidyl choline fraction of soya lecithin (conditions same as for Figure 4 except injection volume 50-250 pJL)...

Figure 7. Effect of sample size on apparent molecular weight for soya lecithin phosphatide fractions (conditions same as for Figures 5 and 6 (O) ethanol-soluble fraction (phosphatidyl choline), oligomer GPC (%) ethanol-soluble fraction (phosphatidyl choline), "main column (l ) ethanol-insoluble fraction (other phos-p hat ides), "oligomer GPC (A) ethanol-insoluble fraction (other phosphatides),...

Most of the permeabilities of the bases decrease steadily as the phospholipid fraction increases. There are some significant exceptions. Metoprolol, which is only moderately permeable in the DOPC lipid, becomes appreciably permeable in 10% soy lecithin. But at the 68% soy level, this molecule also shows reduced transport. 

Einally, LDPE SPMDs with grass carp lipid were exposed for 21 d to 14C-2,2, 5,5 -TCB, 14c-3,3, 4,4 -TCB, i c-mirex and i c-fenvalerate, whereas SPMDs with triolein or lecithin were exposed to only " C-2,2, 5,5 -TCB. After 21 d, the largest mass fraction of these test chemicals ( " C-mirex was an exception) was in the triolein. The C-2,2, 5,5 -TCB log triolein-water partition coefficient was 6.01, whereas the " C-2,2, 5,5 -TCB partition coefficients for the grass carp lipid-water and lecithin-water systems were 30% and 35% lower, respectively. Comparison of these data to literature log AlowS of 2,2, 5,5 -TCB showed that the partition coefficients for the grass-carp lipid and the lecithin were not significantly different from median values reported for the log ATow of " C-2,2, 5,5 -TCB. However, the partition coefficient of 2,2, 5,5 -TCB in triolein and water in direct... 

The aggregation behavior of C21-DA salt in dilute electrolyte medium appears to resemble that of certain polyhydroxy bile salts (25,16). That C21-DA, with a structure quite different from bile acids, should possess solution properties similar to, e.g., cholic acid is not entirely surprising in light of recent conductivity and surface tension measurements on purified (i.e., essentially monocarboxylate free) disodium salt aqueous solutions, and of film balance studies on acidic substrates (IX) The data in Figure 3 suggest that C21-DA salt micelles Incorporate detergents - up to an approximate weight fraction of 0.5 -much like cholate Incorporates lecithin or soluble... 

One of the most striking lipoprotein abnormalities of familial LCAT deficiency is the presence in the LDL fraction of abnormally large particles, containing variable but unusually great proportions of unesteri-fied cholesterol and lecithin (F6, G14, N5). Recently, an abnormal LDL lipoprotein, identical to cholestatic lipoprotein, LP-X (see Section 8.1) was demonstrated in plasma from patients with familial LCAT deficiency (Ml, T2). Identity of the abnormal LDL lipoprotein and LP-X was shown by electron microscopy, composition, and immunological techniques (T2). The amount of LP-X in plasma of patients with obstructive jaundice ranged from 40 to 1200 mg/100 ml (M3) whereas plasma from patients with familial LCAT deficiency contained 49 to 152 mg/100 ml (T2). 

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