PREPARATION OF LOW CHOLESTEROL OIL

Abstract: A process for the continuous removal of cholesterol from a feed oil which comprises (a) wet milling a raw oil having an elevated cholesterol level with an extraction oil whereby there is formed a mixture of the raw oil and extraction oil; (b) centrifuging said mixture to yield a first fraction low in cholesterol, said first fraction being suited for incorporation into a foodstuff, and a second fraction which is an oil feed having a high level of cholesterol; (c) introducing said oil feed at a temperature of at least about 400 DEG F (204.4 DEG C) at an upper portion of a countercurrent thin-film steam stripper while simultaneously introducing steam at a lower portion thereof, wherein said countercurrent thin-film steam stripper is internally configured with sufficient active surface area so that it is capable under appropriate operating flow conditions of temperature, pressure and steam flow rates to remove at least 65 % cholesterol from a cholesterol containing oil, said countercurrent thin-film steam stripper being continuously maintained at a pressure of at least about 1 mmHg and a temperature of at least about 400 DEG F (204.4 DEG C), whereby there is produced a two-phase exit flow therefrom comprising a liquid phase containing oil with reduced level of cholesterol and a vapor phase rich in cholesterol; (d) and recycling said liquid phase as an extraction oil for said wet milling.

Description: PREPARATION OF LOW CHOLESTEROL OIL This application incorporates by reference the entire text of Marschner & Fine, U.S. Patent 4,996,072, granted Feb. 26, 1991, "Physical Process for the Deodorization and/or Cholesterol Reduction of Fats and Oils", including the entire specification and all drawings. BACKGROUND OF THE INVENTION 1. Technical Field The present invention relates to a method for treating fats and oils for cholesterol level reduction. 2. Background The prior art comprises Bracco et al., U.S. Patent 4,333,959, "Decholesterization of Egg Yolk", which discloses colloidal mixing of an oil to be treated and a recycle oil. Such known techniques in the prior art with colloidal mixing are not a part of the present invention. The present invention relates to an improvement in the general process for reducing the level of cholesterol in an oil feed taught by Marschner & Fine, U.S. Patent 4,996,072, granted Feb. 26, 1991. The Marschner & Fine process comprises steps (c) and (d) listed below in the first paragraph under the heading "DETAILED DESCRIPTION OF THE INVENTION". BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and IA are as set forth in the aforementioned and incorporated-by-reference text of U.S. Patent 4,996,072 and comprise a schematic flow chart diagram of one embodiment of the first aspect of the present invention. UNITS OF MEASUREMENT Throughout the specification and claims, percentages and ratios are by weight and temperatures in degrees Fahrenheit and Celsuis unless otherwise indicated. DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a process for the continuous removal of cholesterol from a feed oil which comprises. (a) wet milling a raw oil having an elevated cholesterol level with an extraction oil whereby there is formed a mixture of the raw oil and extraction oil; (b) centrifuging said mixture to yield a first fraction low in cholesterol, said first fraction being suited for incorporation into a foodstuff, and a second fraction which is an oil feed having a high level of cholesterol; (c) introducing said oil feed at a temperature of at least about 400* F. (204.4 β C.) (204.4 β C.) at an upper portion of a countercurrent thin-film steam stripper while simultaneously introducing steam at a lower portion thereof, wherein said countercurrent thin film steam stripper is internally configured with sufficient active surface area so that it is capable under appropriate operating flow conditions of temperature, pressure and steam flow rates to remove at least 65 % cholesterol from a cholesterol containing oil, said countercurrent thin-film steam stripper being continuously maintained at a pressure of at least about 1 mmHg and a temperature of at least about 400* F. (204.4" C), whereby there is produced a two phase exit flow therefrom comprising a liquid phase containing oil with reduced level of cholesterol and a vapor phase rich in cholesterol; (d) and recycling said liquid phase as an extraction oil for said wet milling. In step (a) of wet milling a raw oil having an elevated cholesterol level with an extraction oil whereby there is formed a mixture of the raw oil and extraction oil, the amount of raw oil yolk versus the amount of extraction oil, whether recycled or freshly introduced, is from about one to about four parts by weight of extraction oil per part raw egg oil, and more preferably about two parts extraction oil per part raw egg oil. The wet milling of the present invention involves mixing the ingredients in a high intensity mixer of the type that can be used for making mayonnaise. In a preferred embodiment there may be mentioned a wet milling apparatus sold under the trademark, Fryma VK-7 (Fryma-Maschinen AG, CH-4310 Rheinfelden, Switzerland) . The extraction oil that enters the wet milling process at the commencement of any production run may be either leftover extraction oil from a previous run, extraction oil that has been recycled, fresh oil, or any combination thereof. When a fresh oil is introduced into the procedure, the oil may be of animal or vegetable origin. As examples of oils that may be used as the extraction oil may be mentioned vegetable and animal oils. As vegetable oils may be mentioned soy oil, corn oil and safflower oil. As animal oils may be mentioned lard, tallow, chicken fat or a marine oil, e.g., a fish oil. In a preferred embodiment chicken fat is used as the extraction oil. The temperature of step (a) is not particularly critical. It is recognized that the extraction oil that is recovered in step (c) is at a temperature of at least about 400* F. (204.4° C.) when it exits the steam stripper. Preferably, the oil is permitted to cool, for example, to room temperature, but it is may be used without such cooling, preferably at a temperature of up to about 100° F. (37.8 • C). It is contemplated in a preferred embodiment that wet egg yolk, separated from the egg white, is the raw oil to be used in the invention. It is particularly advantageous to treat the egg yolk as it is notoriously high in cholesterol which is a major drawback to the wider usage of this otherwise wholesome food. In step (b) centrifuging said mixture to yield a first fraction low in cholesterol, the first fraction is suitable for incorporation into a foodstuff. Where wet egg yolk is used as the raw oil in step (a) , in a preferred embodiment the first fraction is a low cholesterol egg yolk product which is then suitable for use, as such, or for mixing with egg white, either for sale as a whole egg product to commercial food processors or for retail sale to homemakers. In the centrifugation step (b) , in one embodiment a batch centrifugation may be used where a simple test tube is centrifuged for a period of five minutes, during which two discrete phases are reached. An extraction oil phase is decanted off and used in step (c) . The remaining egg yolk is then suitable for further processing as a foodstuff. In a second embodiment, a continuous centrifugation process is used which is more suitable for a commercial operation. Through the centrifugation process there is a substantially complete separation of the cholesterol from the egg yolk. The cholesterol is uniformly distributed in the oil phase that is decanted off, thereby permitting an optimum removal of cholesterol. The second fraction from step (b) that is decanted off in the centrifugation process is a cholesterol rich oil that is preferably recycled by first treating that fraction under the procedures of step (c) . Step (c) comprises introducing said oil feed at a temperature of at least about 400" F. (204.4* C.) at an upper portion of a countercurrent thin-film steam stripper while simultaneously introducing steam at a lower portion thereof, wherein said countercurrent thin film steam stripper is internally configured with sufficient active surface area so that it is capable under appropriate operating flow conditions of temperature, pressure and steam flow rates to remove at least 65 % cholesterol from a cholesterol containing oil, said countercurrent thin-film steam stripper being continuously maintained at a pressure of at least about 1 mm Hg and a temperature of at least about 400* F. (204.4* C), whereby there is produced a two phase exit flow therefrom comprising a liquid phase containing oil with reduced level of cholesterol and a vapor phase rich in cholesterol. The vapor phase is rich in cholesterol. It is either discarded or may be retained for recovery of the cholesterol. The step (d) comprising the recycling of the liquid phase returns the remaining oil for use in step (a) . The following examples illustrate the invention: EXAMPLE 1 1 part by weight raw egg yolk is mixed together with 2 parts of an extraction oil that has been obtained by subjecting chicken fat to the process 'of Example 1 of U.S. Patent No. 4,996,072 (Marschner & Fine) , whereby the cholesterol content of the chicken fat has been substantially reduced. A wet milling process is used to create an intimate admixture suitable for centrifugation. The wet milling is conducted in an apparatus sold under the trademark, Fryma VK-7 (Fryma-Maschinen AG, CH- 4310 Rheinfelden, Switzerland) . EXAMPLE 2 A test tube full of the intimately mixed product of Example 1 is then centrifuged for a period of five minutes to yield two phases, a lower, egg yolk-rich phase that is retained for processing as a foodstuff, and an upper phase to be decanted off, and used for step (c) . It is understood that in any commercial operation of the present invention, a conventional, continuous centrifugation process is preferably utilized. EXAMPLE 3 The second, cholesterol-rich fraction which is decanted off in the procedure of Example 2 is thereafter introduced as the oil feed of cholesterol which is substituted for the oil containing native cholesterol in the process of Example 1 of U.S. Patent No. 4,996,072 (Marschner & Fine). The resultant two phase exit flow comprises a liquid phase containing oil with reduced level of cholesterol and a vapor phase rich in cholesterol. The vapor phase is discarded, while the liquid phase is recycled to be used as extraction oil for said wet milling. EXAMPLE 4 The lower, egg yolk-rich phase of Example 2 that is retained for processing as a foodstuff may be used in a variety of ways. The egg yolk-rich phase may be substituted without further processing for egg yolk in a commercial operation where egg yolk, per se, is required either for cooking or baking. Where an egg product is to be made available for sale to consumers it is generally reconstituted together with an appropriate amount of egg white to form a whole egg product. In a preferred embodiment of a reconstituted product, the egg white and the egg yolk-rich phase are mixed together to form a product that is offered to consumers in a "scrambled" form. Pasteurization is optimally included as a processing step whereby any danger of salmonella or other illness inherent in poultry is obviated. Homogenization is also a desirable processing step. EXAMPLE 5 Instead of creating a "scrambled" egg form as in Example 4, it is also possible to form an "egg" in an unscrambled form. The egg-yolk rich phase may be extruded in a conventional manner with pieces of the egg-yolk rich phase being cut into units equivalent to an egg yolk, with the resultant "egg yolk" being treated in conventional means for such reconstitution whereby a solid film encasing the "egg yolk" is formed. A plurality of "egg yolks" is then mixed with egg white under conditions not to break the "egg yolks". EXAMPLE 6 The "scrambled" form of egg of Example 4 has an oil content substantially equivalent to that of a regular, -untreated egg. Whereas the cholesterol component of the oil has been removed in accordance with the process leading to the egg of Example 4, a small amount of oil substantially equivalent to the removed cholesterol is retained. In a preferred embodiment, chicken fat is used as the extraction oil. EXAMPLE 7 Instead of providing the replacement oil from the extraction oil in the same amount as the removed cholesterol as in Example 6, it is possible to include an excess oil of up to about five percent, and preferably not more than about three percent. In this example, the amount of oil in the "scrambled" egg of the invention of Example 4 is increased by one percent. Inclusion of an increased amount of oil facilitates making a scrambled fried egg food product. Having described the invention, the claims define the scope of protection:

Claims: WHAT IS CLAIMED IS: 1. A process for the continuous removal of cholesterol from a feed oil which comprises (a) wet milling a raw oil having an elevated cholesterol level with an extraction oil whereby there is formed a mixture of the raw oil and extraction oil; (b) centrifuging said mixture to yield a first fraction low in cholesterol, said first fraction being suited for incorporation into a foodstuff, and a second fraction which is an oil feed having a high level of cholesterol; (c) introducing said oil feed at a temperature of at least about 400* F. (204.4 * C.) at an upper portion of a countercurrent thin-film steam stripper while simultaneously introducing steam at a lower portion thereof, wherein said countercurrent thin film steam stripper is internally configured with sufficient active surface area so that it is capable under appropriate operating flow conditions of temperature, pressure and steam flow rates to remove at least 65 % cholesterol from a cholesterol containing oil, said countercurrent thin-film steam stripper being continuously maintained at a pressure of at least about 1 mmHg and a temperature of at least about 400* F. (204.4* C), whereby there is produced a two phase exit flow therefrom comprising a liquid phase containing oil with reduced level of cholesterol and a vapor phase rich in cholesterol; (d) and recycling said liquid phase as an extraction oil for said wet milling. 2. A process of claim 1 wherein said first fraction is incorporated into a foodstuff. 3. A process of claim 1 wherein said raw oil is wet egg yolk, whereby there is produced said first fraction which is a lowered cholesterol component of egg yolk. 4. A process of claim 1 wherein said method is operated under conditions to remove at least fifty percent of the cholesterol from said oil feed. 5. A process of claim 1 wherein a vegetable oil is included in said wet milling and forms a component of the recycled oil and the feed oil. 6. A process of claim 1 wherein at least 65 % of the cholesterol is removed from said feed oil. 7. A process of claim 1 wherein an animal oil is included in said wet milling and forms a component of the recycled oil and the feed oil. 8. A process of claim 1 wherein said animal oil is chicken fat.

Inventors: MASSIE CECIL, MASSIE, CECIL
Applicants: SOURCE FOOD TECHNOLOGY INC, SOURCE FOOD TECHNOLOGY, INC.
Application year: 1993
Main classification: A23D7
IPC codes: A23D9, A23L1, C11B1, C11B3