Phosphatidylcholine alcohol fractionation

Alcohol fractionation redistributes the phosphoHpids according to their respective hydrophilic and lipophilic properties (13). A process to produce fractionated phosphoHpids with a phosphatidylcholine (PC) content of more than 30% and a PC/PE (phosphatidylethanolamine) quotient of ca 4 has been developed. With this process it is possible to produce 1000 t per year. 

Soybean lecithin is the predominant source of food and pharmaceutical lecithin because of its availability and outstanding functionality. The composition of crude soy lecithin is shown in Table 14. As a result of the presence of a large amount of neutral oil, crude lecithin is usually de-oiled to improve its functionality. De-oiling is based on the solubility difference of neutral and polar lipids in acetone, in which the phospholipids are precipitated and separated. Alcohol fractionation of de-oiled lecithin can further separate lecithin into an alcohol-soluble fraction that is enriched with phosphatidylcholine and an alcohol-insoluble fraction enriched with phospha-... 

A commercial, nearly oil-free lecithin is prepared by acetone extraction of natural lecithin, which removes all but 2-4% oil and free fatty acids. Then an optional alcohol fractionation step can separate the oil-free lecithin into an alcohol-soluble lecithin enriched in phosphatidylcholine and an alcohol-insoluble fraction enriched in phosphatidylinositol. The choline fraction is an excellent emulsifier for oil-in-water (o/w) emulsions and the inositol fraction for water-in-oil (w/o) emulsions. 

Sosada (46) determined the optimum conditions for fractionation of rapeseed lecithin with alcohols to improve purified lecithin yield and phosphatidylcholine enrichment. 

Further fractionation can separate the alcohol-soluble phosphatidylcholine from the alcohol-insoluble phosphatidylinositol. Commercial products that are alcohol-soluble contain concentrated phosphatidylcholine (40-60%) and only low levels of phosphatidylinositol. The alcohol-insoluble products are enriched in phosphatidylinositol (40-60%), whereas their phosphatidylcholine content is greatly reduced. The phosphatidylethanolamine component is approximately equally partitioned between the two fractions. The alcohol-soluble grades tend to be more oil-in-water emulsifiers, whereas the alcohol-insoluble grades are more effective in water-in-oil systems (7). 

To obtain individual phospholipids of greater than 50-60% purity, some form of selective adsorption process is usually required. Adsorption and distribution chromatography present these options. Treatment of the alcohol-soluble lecithin with alumina yields a fraction very rich in phosphatidylcholine and free of phosphatidylethanolamine and phosphatidylinositol (167). Although these products are available only in very limited quantities for highly specialized markets, products such as a lecithin containing up to 95% PC can be obtained commercially. 

Cmde fractions can be obtained by solvent fractionation treatments utilizing lower alcohols, such as ethanol, or alcohol-water mixtures. The product is a soluble fraction rich in phosphatidylcholine, whereas phosphatidic acid and phophatidyli-nositol predominate in the insoluble fraction. The shift in the ratio of phosphatidylcholine to phosphatidylethanolamine improves the emulsification and antispattering capabilities of the soluble fraction. The products of this process can be used as they are or can be further purified with adsorbents. The soluble fraction is an excellent oil-in-water emulsifier and is predominately used in margarine. The acidic phospholipids of the insoluble fraction are used in water-in-oil systems. The chocolate manufacturing industry uses this fraction to increase the viscosity of chocolate masses, thereby reducing the requirement for cocoa butter (83, 84). 

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