Membrane degumming

Various researchers have reported on attempts to remove fatty acids from oils by ultrafiltration membranes. In the absence of membranes that can withstand extraction solvents, success generally has been limited. However, progress has been made on membrane degumming.111... 

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. 

Recently, polymeric ultrafiltration membranes were used for degumming crude soybean oil and removing phospholipids from the crude oil/hexane miscella (168). Crude soybean oil also can be de-acidified by methanol extraction of the free fatty acids and the extract separated into fatty acids and solvent by a membrane filter (169). A surfactant-aided membrane degumming also has been applied to crude soybean oil, and the degummed oil contained 20-58 ppm of phosphorus (170). Supercritical carbon dioxide extraction was shown to be an effective means of degumming (171). In this process, soybean oil countercurrently contacted supercritical carbon dioxide at 55 MPa and 75°C. The phosphorus content of the oil was reduced from 620 ppm to less than 5 ppm. Ultrasonic degumming was also successfully used to reduce the gum content of soybean oil (172). 

Membrane degumming. Membrane separation has also been evaluated as an alternative process to conventional oil refining processing. Ultrafiltration (UF) and nanofiltration (NF) membranes separate phospholipids almost completely, and FFAs, pigments, and other components can also be removed with the phospholipids to a certain extent. Less effort is required in the later processing steps. 

TABLE 4. Comparisons of Reported Membrane Degumming Conditions and Results. 

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

The micellar-enhanced ultrafiltration MEUF technique, based on addition of surfactants and chelating agents to complex and enhance removal of undesirable compounds, show considerable promise in membrane degumming applications. The natural substances such as phospholipids act as surfactants to form large micelles that will be rejected by the membrane. 

Membrane degumming can be performed either with the miscella, generally 20%-30% of crude oil in hexane, m/m, and with the crude oil without the addition or removal of solvent. 

Lin, L., Rhee, K. C., and Koseoglu, S. S. (1997) Bench-scale membrane degumming of crude vegetable oil Process optimization. Journal of Membrane Science 134, 101-108. 

De BK, Das R, Dutta BK, Bhattacharyya DK. 1998. Membrane Degumming and Dewaxing of Rice Bran Oil and Its Refining. Lipid/Fett 100(9) 416-421. 

Lin L, Rhee KC, Koseoglu SS. 1997. Bench-Scale Membrane Degumming of Crude Vegetable Oil Process Optimization. Journal of Membrane Science 134(1) 101-108. 

Subramanian R, Nakajima M. 1997. Membrane Degumming of Crude Soybean and Rapeseed Oils. J. Am. Oil Chem. Soc. 74(8) 971-975. 

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