Vegetable Oil Degumming

Ochoa, N., Pagliero, C., Marchese, J., and Mattea, M. (2001) Ultrafiltration of vegetable oils. Degumming by polymeric membranes. Separation and Purification Technology 22-23, 417-422. 

Koris, A., Edit, M. (2006). Ceramic ultrafiltration membranes for non-solvent vegetable oil degumming (phospholipid removal). Desalination, 200, 537—539. 

The total commercial lecithin potential if all vegetable oils were degummed worldwide would be 552,000 t (Table 7). Although soybean, sunflower, and rape lecithins are available in the market, the principal commercial interest is only in soybean lecithin. The aimual worldwide production is 130,000 t (Table 8). 

In commercial formulations, phospholipids are not available as pure products. Mostly they are obtained as a by-product of the process of refining vegetable oils, during the so-called degum-ming step (3,4), from which a liquid-to-pasty product is obtained that is referred to as lecithin. Lecithin contains about 65% phospholipids plus about 30% residual neutral lipids and minor amounts of glycolipids. For historical reasons, most commercially available lecithins are derived from soybean oil, but lecithins of other oils could be used as well. From this discussion it follows that the determination and quantification of phospholipids is of importance both to control how efficiently the phospholipids have been removed from vegetable oils and to control the quality of the lecithin. For this purpose it is important to know not only the total amount of phospholipids but also the amount of the different types of phospholipids present, because it is well known that the functional properties of the various phospholipids differ widely (2-8). 

Vegetable oils are refined through pressing/extraction, degumming, alkali deacidification, decolorization, and deodorization. Alkali deacidification byproduces soapstock. Acidulation of soapstock prepares acid oil which contains FFAs, acylglycerols, and other lipophilic compounds. It is reproduced currently as FFAs, which are used as raw materials for production of soaps, lubricants, and paints. But the demand for FFAs is almost in saturation. Hence, conversion of acid oil to BDF is expected to avoid an oversupply of the industrial FFAs and subsequent price decrease. 

Peroxide Value, Fats and Oils (PV) (Cd 8-53) determines all substances, in terms of milliequivalents of peroxide per 1000 g of sample, that oxidize potassium iodide (KI). These substances generally are assumed to be peroxides or products of fat oxidation. Phosphorus in Oils (Ca 13-55) estimates the phospholipid content of crude, degummed, and refined vegetable oils in terms of phosphorus. Refineries often use induction coupled plasma (ICP) spectrographs to analyze divalent cations rapidly in aspirated crude oil. The calcium and magnesium measured are mainly responsible for nonhydratable phosphatides (NHP) and are determined directly. An AOCS method for analysis by ICP is being developed. 

Lin, L., Rhee, K. C., and Koseoglu, S. S., Recent progress in membrane degumming of crude vegetable oils on a pilot-plant scale, in Advances in Oils and Fats, Antioxidants, and Oilseed By-Products, S. S. Koseoglu, K. C. Rhee, and R. F. Wilson (Eds.), pp. 76-82, AOCS, Champaign, IL, 1998. 

EnzyMax A process for degumming vegetable oils by use of the enzyme phospholipase A2, which converts water-insoluble phospholipids into hydratable phospholipids that can be extracted with water. Developed by Lurgi and first installed at Shenzen, China. 

E.g., Vegetable oil, WVO, animal fat, yellow grease (filtered degummed)... 

Figure 3 (111). Recommended conditions for degumming of crude vegetable oils can vary greatly as shown in Table 22 (111, 117-124).

Nonhydratable phospholipids. According to Myers (138), about 90% of the phospholipids are removed from the oil by water degumming. Although most of the remaining phospholipids are removed by alkali neutralization, Braae et al. (139) report that soybean oil and several other types of vegetable oils often contain some phospholipids that are not removed by alkali neutralization and washing. 

The conventional crude oil refining process consists of four steps (2,4—6). The first step is degumming to remove the phospholipids. Cmde vegetable oils can either be... 

Degumming with acetic anhydride. The process is referred to as the Staley 50 process. Acetic anhydride (0.1%) is mixed with preheated oil (60-70°C) for 15 min, and the mixture is stirred for 30 min after the addition of 1.5% water. The degummed oil obtained is claimed to require no caustic refining. However, the Staley process does not work well with highly colored vegetable oils like cottonseed oil (5). 

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). 

Subramanian, S., Nakajima, M., Yasui, A., Nabetani, H., Kimura, T. and Maekawa, T. (1999) Evaluation of surfactant-aided degumming of vegetable oils by membrane technology. J. Am. Oil Chem. Soc., 76, 1247-1253. 

Acid degumming of sunflower oil is not generally required because of the low concentration of the phospholipids in the oil. Some processors degum poor quality sunflower oil with citric acid treatment. The results are satisfactory. However, this is not commonly followed in the sunflower processing industry. Some processors also pre-treat crude sunflower oil with phosphoric acid or citric acid before chemical refining. This is a common practice for refining most vegetable oils. 

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