Method of manufacturing a sterol ester mixture

Organic compounds -- part of the class 532-570 series – Organic compounds – Fatty compounds having an acid moiety which contains the...

Reexamination Certificate

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C554S156000, C554S195000, C426S478000, C426S489000

Reexamination Certificate

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06492538

ABSTRACT:

The present invention relates to a method for the manufacture of an ester mixture, in particular an ester mixture of phytosterols and phytostanols (4-desmethylsterols, 4-monomethylsterols and 4,4′-dimethylsterols and their stanol equivalents) (hereinafter called sterols) and fatty acids.
High cholesterol levels in blood serum can cause an increased risk of coronary heart diseases. Several methods have been proposed for reducing cholesterol levels.
A well-known method relates to a careful selection of fatty acids in the diet, in particular a diet rich in unsaturated fatty acids can help to reduce cholesterol levels.
Another method relates to the addition of specific substances to the diet to lower the cholesterol level. For example WO 92/19640 disloses the use of &bgr;-sitostanol ester for lowering cholesterol levels in serum.
It was found that particular sterol derivatives have better cholesterol lowering properties than others. A number of sterols occur in nature which are esterified. For example, the majority of sterols, i.e. 25-80%, found in sources like corn, wheat, oat, rice bran and sheanut are esterified with phenolic acids such as ferulic acid, coumaric acid, caffeic acid, and cinnamic acid. However, it has been found that these esterified sterols are less suitable for lowering cholesterol-levels in serum.
This means that for the majority of sterol derivatives occurring in sources like corn, wheat, oat, rice bran and sheanut, there is a desire for improvement for their blood cholesterol lowering effects.
Further, it has been found that a significant part of sterols is not esterified at all. This type of sterols is not easily soluble in oils, and so not very suitable as a good source for applications in fat based food products.
U.S. Pat. No. 3,751,569 suggests the use of esters of monocarboxylic acid and plant sterols in dietary oils for reducing the cholesterol level.
A disadvantage of the methods of WO 92/19640 and U.S. Pat. No. 3,751,569 is the high costs of the ester materials. These high costs are due to the high isolation and preparation costs for the materials.
All methods known to day for making ester materials use free sterols as occurring in nature as the starting material for obtaining ester mixtures. Also, in nature, a number of sterol esters exists that were found that are not as effective in blood cholesterol lowering as the fatty acid esters of phytosterols and phytostanols.
Where in this application sterols are mentioned, phytosterols, phytostanols or mixtures thereof are meant. Hence, the term sterols in this application refers to 4-desmethylsterols, 4-monomethylsterols and 4,4′-dimethylsterols, their stanol equivalents, and mixtures thereof in any of combination possible.
The present invention aims at providing a cheap process for the preparation of an ester mixture, said ester mixture having a cholesterol lowering effect on foods. By the presently found method, it is now possible to have all sterols and sterol derivatives present in fat rich sources, but which up till now were not suitable for obtaining sterol derivatives that have a significant blood cholesterol lowering effect. Moreover, the blood cholesterol lowering effect obtainable by the use of the total amount of sterols and sterol derivatives present in these sources was found to be increased. Thus, the amount of effective cholelesterol lowering sterol derivatives obtainable from sources used in the past is increased, and many more sources applicable for obtaining such effective sterol derivatives have become available.
It has been found that the costs for producing the ester mixture can significantly be reduced if materials other than free phytosterols (U.S. Pat. No. 3,751,569) or their derivatives (WO 92/19640) are used as the starting material and the process involves a specific hydrolysation step.
Further advantages of the process of the invention are that the process can be carried out without the need for high investments, the process can easily be carried out at a high yield and the level of wastage is low, because the by-products can be used for other purposes.
Further advantages are that the specific ester mixture obtained by the process of the invention can very conveniently be incorporated in food products at relatively high levels. They also show excellent abilities to reduce serum cholesterol levels.
Accordingly in a first aspect the present invention relates to a process for the manufacture of an ester mixture comprising the steps of:
(a) hydrolysing a sterol ester or a mixture of sterol esters such that a mixture is obtained comprising phenolic and/or fatty acids, and free sterols; and
(b) esterifying the so obtained free sterols with particular fatty acids.
In another aspect, the invention relates to a process for the manufacture of an ester mixture comprising the steps of:
(a) hydrolysing a sterol ester or a mixture of sterol esters such that a mixture is obtained comprising phenolic acids and/or fatty acids, and free sterols; and
(b) separating the phenolic acids and/or fatty from the reaction mixture; and
(c) esterifying the so obtained free sterols with particular fatty acids.
The method is very beneficial if the sterol esters are esters of sterols and acids other than fatty acids. In this embodiment, the sterol ester or mixture of sterol esters is a mixture comprising phenolic acid sterol esters. In a further preferred embodiment, the process is a process wherein the sterol ester or mixture of sterol esters consist of a phenolic acid sterol ester or a phenolic acid sterol ester mixture.
In a particular embodiment the invention concerns a process for the manufacture of an ester mixture comprising the steps of:
(a) hydrolysing &ggr;-oryzanol such that a mixture is obtained comprising ferulic acid and sterols; and
(b) separating the ferulic acid from the reaction mixture; and
(c) esterifying the so obtained sterols with particular fatty acids.
In particular, the present invention encompasses sterol fatty acid ester mixtures obtainable by the method of the present invention. If in the process of the invention, sterols of one particular source are used without modification, the nature and tatio of the sterols found in the product resulting from the process of the present invention will be indicative of the source used. In one embodiment of the present invention, the sterol fatty acid ester mixtures is characterised by the nature of the type of sterols found in the sterol esters and the ratio of the different sterol, the nature and ratio being similar to those found in the sterol derivatives present in rice bran.
In yet another embodiment, nature and ratio of the alcohol part found in the sterol fatty acid ester mixture of the invention are similar to those found in the sterol derivatives present in shea.
In the case there is a desire to prepare fatty acid sterol esters of a further definked fatty acid type, the process indicated above can also be applied for re-esterifying fatty acid sterol esters with a further defined group of fatty acids. With particular fatty acids is meant in this application a group of fatty acids chosed as desired.
In a most preferred embodiment of this invention, sterol esters are used that are esterified with any phenolic acid. In nature, most phenolic acid sterol esters are esters of sterols and phenolic acids from the group of ferulic, coumaric, caffeic, and cinnamic acid.
Sterol esters that are in particular suitable for the method of the present invention are the sterol esters from rice bran and from sheanut.
The sterol esters and stanol esters can be isolated from natural sources by known techniques. If so desirable, the sterol esters can be hardened to stanol esters, before or after the process of re-esterification.
A particular suitable sterol esters group to be re-esterified is oryzanol. Oryzanol or &ggr;-oryzanol is a mixture of ferulic acid esters of mainly the phytosterols campesterol, &bgr;-sitosterol, 24-methyl-cycloartenol and cycloartenol. &ggr;-oryzanol is present as a minor component at relatively high levels in rice-bran

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