Food or edible material: processes – compositions – and products – Inhibiting chemical or physical change of food by contact... – Treating liquid material
Reexamination Certificate
1999-01-14
2001-03-27
Paden, Carolyn (Department: 1761)
Food or edible material: processes, compositions, and products
Inhibiting chemical or physical change of food by contact...
Treating liquid material
C426S417000, C426S422000, C426S478000, C426S490000, C554S175000, C554S177000, C554S206000, C134S040000, C210S348000, C210S650000, C210S651000
Reexamination Certificate
active
06207209
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for removing phospholipids from vegetable oil miscella, a method for conditioning a polymeric microfiltration membrane for selective removal of phospholipids from miscella, and membrane.
BACKGROUND OF THE INVENTION
Edible vegetable oils are generally obtained by processing oil seeds. Crude vegetable oils can be obtained from vegetable seeds by solvent extraction. Hexane is the most commonly used extraction solvent. The crude vegetable oils generally contain neutral triglycerides and a host of natural contaminants including phosphotides, sulphurous compounds, free fatty acids, carbohydrates, peptides, oxidized lipids, traces of lower aldehydes and ketones, glycosides of sterols and terpenes, and diverse types of color bodies or dyestuffs. These contaminants are removed from the crude vegetable oils in the course of refining in order to render the vegetable oils palatable.
The recovery of soybean oil from soybeans is particularly desirable. A technique for recovering soybean oil includes several processing steps. The soybean is dehulled and crude soybean oil is extracted with hexane. The extractant (miscella), which includes hexane and crude soybean oil, is further processing to recover palatable soybean oil. The hexane is evaporated from the miscella and the resulting crude soybean oil is degummed. Degumming, as used in conventional processes, refers to the removal of phosphatides and other gums from the oil by adding water and/or acid thereto and centrifuging. The recovered oil can be further refined with water and alkaline (such as NaOH) and centrifuged to remove the fatty acids and gums. The oil resulting from the alkaline refining step can then be bleached to remove color bodies, hydrogenated to render the oils more stable, and deodorized. The techniques of degumming, alkaline refining, bleaching, hydrogenating, and deodorizing are well known in the art. It should be appreciated that each separation step, and particularly centrifuging, results in loss of oil.
Numerous prior art references describe techniques for obtaining vegetable oils by application of membrane technology. For example, U.S. Pat. No. 4,093,540 to Sen Gupta describes refining crude glyceride oils by contacting a composition of glyceride oils and organic solvent under pressure with a semi-permeable ultrafiltration membrane to separate constituents of different molecular weight into retentate and permeate fractions, and contacting the composition or at least one of the fractions with a metal oxide or metalloid oxide adsorbent in a column containing the adsorbent. Additional references which describe the use of membrane technology for separating phospholipids from crude vegetable oils include: U.S. Pat. No. 4,414,157 to Iwama et al.; U.S. Pat. No. 4,533,501 to Sen Gupta; Raman et al., “Membrane Technology”, Oils & Fats International, Vol. 10, No. 6, 1994, pages. 28-40; Ziegelitz, “Lecithin Processing Possibilities”, Inform, Vol. 6, No. 11, Nov. 1995, pages. 1224-1213; Ondrey et al., “The Skinny On Oils & Fats”, Chemical Engineering, Oct. 1997, pages. 34-39; Pioch et al., “Towards An Efficient Membrane Based Vegetable Oils Refining”, Industrial Crops & Products, 7 (1998) pages 83-89; Koseoglu et al., “Membrane Applications & Research In The Edible Oil Industry: And Assessment, JAOCS, Vol. 67, No. 4 (April 1990), pages 239-249.
SUMMARY OF THE INVENTION
A method for removing phospholipids from vegetable oil miscella is provided by the present invention. The method includes a step of feeding vegetable oil miscella to a membrane for recovery of a permeate stream and a retentate stream, and recovering the permeate stream having decreased weight percent of phospholipids compared with the weight percent of phospholipids provided in the miscella.
In the context of the present invention, the permeate stream is the stream which flows through the membrane, and the retentate stream is the stream which does not flow through the membrane. The vegetable oil miscella includes extraction solvent and crude vegetable oils containing phospholipids. The membrane includes a polymeric microfiltration membrane conditioned for selective separation of phospholipids from the miscella to provide a permeate stream having a decreased weight percent of phospholipids compared with the weight percent of phospholipids provided in the miscella. The microfiltration membrane, prior to modification, is preferably provided having an average pore size in the range of about 0.1&mgr; to about 2&mgr;.
The vegetable oil miscella preferably contains between about 45 percent by weight and about 90 percent by weight extraction solvent, and more preferably between about 70 percent by weight and about 80 percent by weight extraction solvent. A preferred extraction solvent includes hexane. The permeate stream preferably includes less than 0.6 weight percent phospholipids, more preferably less than about 0.15 weight percent phospholipids, and even more preferably less than about 0.015 weight percent phospholipids.
A method for conditioning a microfiltration membrane is provided by the invention. The method includes providing a polymeric microfiltration membrane characterized as having an average pore size in the range of about 0.1&mgr; to about 2&mgr;. Preferably, the polymeric microfiltration membrane comprises polyacrylonitrile, polysulfone, polyamide, or polyimide. The polymeric microfiltration membrane can be conditioned by treating the membrane with an intermediate solvent, and then treating the membrane with an extraction solvent. A preferred embodiment of the invention includes treating the membrane with a mixture of intermediate solvent and extraction solvent between the steps of treating the membrane with an intermediate solvent and treating the membrane with an extraction solvent.
The steps of treating the membrane with solvent are conducted for a period of time which is sufficient to provide the desired level of conditioning. In most cases, it is expected that the treatment will include flushing and/or soaking for at least about one half hour. For convenience, it may be desirable to allow the membrane to soak in the particular solvent over night or for a period of up to about 24 hours. It should be understood that longer soaking times are permitted.
The treatment with the intermediate solvent is advantageous to reduce the likelihood of shocking or harming the membrane when treated with the extraction solvent. Exemplary intermediate solvents include alcohols and acetone. Preferably, the intermediate solvent is one which is miscible with the extraction solvent. In the case of using hexane as the extraction solvent, the intermediate solvent is preferably ethanol, propanol or a mixture of ethanol and propanol.
A conditioned polymeric microfiltration membrane is provided by the invention. The conditioned membrane can be characterized as a membrane resulting from the steps of conditioning. In addition, the conditioned membrane can be characterized in terms of its performance. For example, a soybean oil miscella can be providing containing 25 percent by weight crude soybean oil and 75 percent by weight hexane, and containing a phosphorous level of about 5,000 ppm in the crude oil. By feeding the miscella to the membrane at a transmembrane pressure of about 150 psi, it is expected that the membrane will provide a steady state permeate at a flux of greater than about 65 l/hr m
2
and a phosphorous level of less than about 50 ppm. Preferably, the phosphorous level will be less than about 25 ppm. More preferably, the flux will be greater than about 80 l/hr m
2
.
REFERENCES:
patent: 4062882 (1977-12-01), Sen Gupta
patent: 4093540 (1978-06-01), Sen Gupta
patent: 4414157 (1983-11-01), Iwama et al.
patent: 4496489 (1985-01-01), Sen Gupta
patent: 4533501 (1985-08-01), Sen Gupta
patent: 4787981 (1988-11-01), Tanahashi et al.
patent: 4797200 (1989-01-01), Osterhuber
patent: 5166376 (1992-11-01), Suzuki et al.
patent: 5207917 (1993-05-01), Weaver
patent: 5310487 (1994-05-01), LaMonica
patent: 5374356 (1994-12-
Jirjis Bassam
Muralidhara Harapanahalli S.
Otten Dennis D.
Cargill Incorporated
Merchant & Gould P.C.
Paden Carolyn
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