De-oiling of Raw Lecithin by High Pressure Extraction Processes

Volkmar Steinhagen1, Dr. Christoph Lütge1, Michael Bork1, Maša Knez Hrnčič3, Željko Knez2,3

1 Uhde High Pressure Technologies GmbH, 58093 Hagen, Germany 2 CINS d.o.o, SI 2000 Maribor, Slovenia

3 University of Maribor, Faculty of Chemistry and Chemical Engineering, Laboratory for Separation Processes and Product Design, SI 2000 Maribor, Slovenia

Corresponding author: volkmar.steinhagen@thyssenkrupp.com; Ph.: +49 2331 967-381; Fax: +49 2331 967-370

ABSTRACT The development of a new process for de-oiling of raw lecithin (dried degumming residue) is presented. Research on laboratory scale was later verified on a pilot scale plant and in next step in a small scale production plant. In each scale the target concentration of minimum 95% of phospholipids was reached in a free flowing powderous product. A production plant for the continuous supercritical de-oiling of soy raw lecithin with carbon dioxide was designed, engineered, assembled, started up and it is in operation since middle of the year 2007. INTRODUCTION Separation and formulation of products by supercritical fluids and production of substances and composites with unique properties and characteristics for the use in different applications are now days intensively studied. One of the most important advantages of the use of supercritical fluids is the design of solvent free products with special product properties. Lecithin is a natural emulsifier, which is found in high concentrations in soy beans and it is a by-product of the soy bean oil production. It is used as a nutraceutical, as emulsifying agent in the food industry and as a source for phosphatidylcholine (PC) in the pharmaceutical industry. Soy lecithin is mainly used in the food industry. Lecithin is not a single substances but a mixture of different phospholipids: phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatoic acid (PA) and others [1]. The raw lecithin, with a typical content of 50% of phospholipids, is conventionally de-oiled by acetone to form a pure lecithin in powderous or granular shape with phospholipids content of approx. 97%. Supercritical CO2 processing of raw lecithin is an alternative to overcome the problems of acetone residues in the de-oiled lecithin and extracted oil. The conventional process need solvent recovery and processing plants have to be explosion-proof. The demand of green products requires the use of green solvents - like CO2 [2-7]. De-oiling of lecithin using supercritical fluids was investigated by several research groups [8-14] but up to our new developed process no application on industrial scale was carried out. The development of a new process was started to establish a feasible process leading to a production scale plant, which produces lecithin powder with a minimum content of 95% of phospholipids. Fundamental thermodynamic data as well as mass transfer, mechanical design of industrial-scale equipment, influence of process parameters on lecithin particle size and particle size distribution, particle shape and modeling of extraction process was studied. PROCESS DEVELOPMENT Thermodynamic data For the process design solubility measurements and phase equilibrium observations were performed for the system raw lecithin (50% phospholipids)/CO2 in a variable volume high pressure view cell which was supplied by NWA (Lörrach – D) presented on Figure 1.

(a)

TI

TIC

PI

CO2

(b) Figure 1: High pressure view cell: flow sheet (a) and photo (b) of the apparatus (60 mL, max. operating pressure 700 bar and max. operating temperature 250°C)

Solubility measurements were performed in a pressure range up to 600 bar and at temperatures of 40°C and 60°C. Results are presented in Figure 2.

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wt.% CO2

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Figure 2: Phase diagram for the system raw lecithin (50% phospholipids)/CO2

Influence of pressure, temperature and stirring rate on:

• distribution of liquid and gaseous phases – possible phase inversions, • qualitative evaluation of viscosity of mixtures, • separation of phases after intensive stirring,

was observed. In the range of applied pressure and temperature (up to 520 bar at 62°C and 700 bar at 40°C) the distribution of phases was such that the phospholipids rich phase (liquid phase) was the bottom phase and the CO2 rich phase containing dissolved oil (gaseous phase) was the upper phase. Lab-scale extraction experiments Tests were carried out in a 10 litre laboratory scale plant at 400 bar and 500 bar at a constant temperature of 60 °C. The specific CO2 flow rate, which is defined as kilogram of CO2 per kilogram of raw material, was varied between 75 and 225 kg/kg and it is shown in Figure 3. As could be seen from Figure 3 the phospholipids content in the de-oiled product is widely independent from the specific CO2-demand at the tested condition.

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Spec. CO2 [kg/kg]

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Figure 3: Phospholipids content (AIM) vs. specific CO2 flow rate

Pilot scale extraction experiments The tests were carried out at 400 bar and 60 °C with specific CO2 flow rates ranging from 100 kg/kg to 200 kg/kg. During each test run totally 200 kg of raw lecithin were extracted resulting in approx. 100 kg of powderous de-oiled lecithin. As it was found out during the lab-scale tests, also the pilot scale up tests shows that the de oiling efficiency is independent from the specific CO2 flow rate in the range between 100 kg/kg and 200 kg/kg.

Production plant design, construction and start up As the result of the experimental studies a production plant was designed, based on the parameters, which were obtained and verified in different scale tests. Beside the degree of de-oiling and the powdery shape it is essential to prevent oxidation of phospholipids in the final product. The basic process flow diagram of the unit is presented in Figure 4a and a photo of the unit is presented in Figure 4b. Because de-oiled lecithin is a powderous product (electronic microscope picture of lecithin particles could be seen on Figure 5) the extractor has to be emptied batch-wise during the process without interruption of feeding. This has the advantage of a more effective and economic operation of the de-oiling process and ensures that the sensible product will not come into contact with oxygen from air.

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Figure 4: a) basic process flow diagram of industrial plant, b) photo of industrial plant

Figure 5: View of lecithin particles produced in industrial scale plant

CONCLUSIONS A green process for processing of the highly viscous raw lecithin was developed from laboratory scale up to industrial plant scale. The main advantages using supercritical CO2 instead conventional solvents (which contaminate lecithin with organic solvents which can not be easily removed) are presented. Examples on selective extraction and further fractionation of components of lecithin from raw lecithin are presented. Fundamentals, like phase equilibrium data for the system oil/SCF as well as mass transfer data will be given in the presentation. Mechanical design of industrial-scale equipment, influence of process parameters on lecithin particle size and particle size distribution, particle shape, modeling of extraction procedure of the process will be presented. REFERENCES [1] HORROCKS, L. A., in: SZUHAJ, B.F., (Ed.), Lecithins: Sources, Manufacture and Uses, American Oil

Chemists Society, Champaign, IL, 1989 [2] SCHNEIDER, M., in: SZUHAJ, B. F., (Ed.), Lecithins: Sources, Manufacture and Uses, American Oil

Chemists Society, Champaign, IL, 1989 [3] MONTANARI, L., FANTOZZI, P., SCHNEIDER, J.M., KING, J.W., J. Supercrit. Fluids, Vol. 14, 1999, p.

87 [4] LIST, G.R., KING, J.W., JOHNSON, J.L., MOUNTS, T.L., J. Am. Oil Chem. Soc., Vol. 70, 1993, p. 473 [5] TEMELLI, F., J. Food Sci., Vol. 57, 1992, p. 440 [6] PETER, S., in: KING, J.W., LIST, G.R., (Eds.) Supercritical Fluid Technology in Oil and Lipid Chemistry,

AOCS Press, Champaign, 1996, p. 82 [7] BRUNNER, G., PETER, S., Sep. Sci. Tech., Vol. 17, 1982,p. 199 [8] STAHL, E., QUIRIN, K.W., Fette Seifen Anstrichmittel, Vol. 87, 1985, p. 219 [9] PETER, S., WEIDNER, E., TIEGS, C., EP 0156374, 1985 [10] WEIDNER, E., ZHANG, Z., CZECH, B., PETER, S., Fat Sci. Technol., Vol. 95, 1993, p. 347 [11] PETER, S., WEIDNER, E., JAKOB, H., Chem. Ing. Tech., Vol. 59, 1987, p. 59 [12] BEN-NASR, H., KRIEGEL, E., REIMANN, K., DE 4010400, 1991 [13] ROSOLIA, F., DE 3936031, 1990 [14] HEIDELAS, J., Agro Food Industry Hi-Tech, Vol. 8, 1997, p. 9