Degumming process

Cmde soy lecithin is obtained as a by-product during the degumming process of soy oil. The phosphoms-containing compounds are removed to improve the stabiHty of the oil. 

Fats and Oils. The oxidation of fats and oils in food products can be prevented by the addition of citric acid to chelate the trace metals that catalyze the oxidation. Citric acid is also used in the bleaching clays and the degumming process during oil refining to remove chlorophyll and phosphohpids (59—63). 

The innermost and outer layers of the cocoon are regarded as waste material, as are inferior cocoons, or those that already hatched. This material is degummed and carded, yielding short-fiber silk that is called schappe. The degumming process of these fibers often involves fermentation in manure. 

A whole variety of processes have been developed to improve the removal of the nonhydratable phosphatides. The best known are the uni-and superdegumming processes (unilever) and the TOP degumming process (vandemoortele). They are principally based on a special acid treatment of the NHP. Over the last few years, several new technological approaches have been developed, which guarantee very low levels of phosphorus (less than 10 ppm). 

In the enzymatic degumming process, part of the hydratable phosphatides is enzymatically modified by removing the fatty acid on the C-2 position of the glycerol, using a phospholipase A2 enzyme as biocatalyst. These modified phosphatides facilitate the removal of the remaining NHP. Table 4.10 shows the results of an enzymatic degumming... 

In the soft-degumming process, a chelating agent (EDTA) is added to the oil to remove the cations from the nonhydratable phosphatides, thereby making them hydratable again (Table 4.11) [4]. 

Figure 4.6 Generalized flow sheet for degumming process. (Source Courtesy of DeSmet Group, Antwerp, Belgium.)...

Phospholipids The phospholipid content of crude sunflower oil ranges between 0.5% and 1.2%. Oils extracted by solvent generally have a higher content of phosphlipids than those obtained by pressing. Major phospholipids are phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and phosphatidic acid. Most are hydratable and may be removed from the cmde oil through a water-degumming process (See Section 5.3.1.)... 

Most published research is into the content and composition of unremoved phospholipids in sunflower oil after different degumming processes. Little research has been done, however, of the separated lecithins. Some conclusions may still be reached about efficiency of production method, as well as the possible composition of these lecithins from the composition of the phospholipids remaining in the oil. 

Two principal degumming methods are employed batch and continuous. The batch degumming process is shown in Figure 2 (115). A flow sheet for the continuous degumming of soybean oil and production of soybean lecithin is shown in... 

Other degumming agents considered include acetic, oxalic, boric, and nitric acids (150) and surfactants (151). However, none of these are currently used in lecithin manufacture. Ringers (152) obtained good results in a two-step degumming process wherein an edible acid, presumably citric, was used. Soybean oil can also be degummed by heat, but this practice is confined to oils going into industrial uses. 

Lecithin and Individual Phospholipids from Degumming Process... 

From a commercial point of view, soybean is the most important source for lecithin however, lecithin production from sunflower (180) and rapeseed (181-183) wet gum has also been successful. Wet gum is removed during the first refining step of crude oil that is the degumming process. Traditionally, crude oil obtained from solvent-extraction process is agitated with 1-3% water at elevated temperatures (70-80°C). Under these conditions, phosphohpids and glycohpids start to swell and become insoluble in the oil. The hydrated mass is removed via centrifugation, and the dehydration is carried out under vacuum until the residual moisture is below 1%. 

The effectiveness of the conventional degumming process is very much dependent on the quality of the crude oil inferior quality oils show incomplete degumming with a single process pass. Moreover, about 20% or more of the phospholipids are lost by destructive treatments and as much as 1% of the neutral oil may be lost. Considerable effluent disposal problems arise as well (8). 

Continuous ultrasonic degumming. Ultrasonic action can generate extremely localized heat and pressure and produce intimate contact of reactants without substantially raising the temperature of the final products. Moulton and Mounts (14) proposed a continuous ultrasonic degumming process in 1990. Compared with a... 

Figure 5. Diagrams for the existing chemical refining process and the proposed membrane degumming process (32).

Glycerophospholipids (PL) are abundant lipid components found in Nature [1]. Most vegetable oils, fish oil and egg yolk are particularly rich in mixtures of phospholipids. They are characterized by the presence of a polar head and two fatty acid chains in the apolar part of the molecule. The two acyl chains mainly consist of saturated fatty acid residues in the snl position and mainly (poly)unsaturated fatty acid chains in the sn2 position. Mixtures of phospholipids at low cost are obtained from the degumming process of vegetable oils. Lecithin, the main component of the mixture, has the polar head characterized by the choline residue. It is usually defined as phosphatidyl choline (PC) and it is understood that the composition of the apolar part is composed of mixtures of fatty acid residues dependent to a large extent on the source of the raw material (fatty acid chains composition of PC from soy beans palmitic 11.6%, stearic 3.4%, oleic 4.6%, linoleic 66.4%, linolenic 8.7%). Scheme 1 shows a PC with two defined acyl chains at the glycerol backbone l-palmitoyl-2-linoleoyl-5n-glycero-3-phosphocholine (PLPC). 

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