Process for preparing OAT lipids

Abstract

A method of separating polar lipids and non-polar lipids contained in a crude oat oil. An oil fraction enriched in polar lipids obtainable by said method, and the used of the oil fraction in consumer products as an emulsifier.

Description

[0001] PROCESS FOR PREPARING OAT LIPIDS

[0002] Field of the Invention

[0003] The present invention relates to a method of separating polar and non-polar lipids contained in an oat oil to provide an oil fraction that is enriched in polar lipids and an oil fraction that is enriched in non-polar lipids. The invention further relates to said oil fractions, their use as functional ingredients in consumer products, and to consumer products containing same.

[0004] Background of the invention

[0005] Oat oils obtained from oat grains or oat flour principally by solvent extraction consist mainly of starches, sugars, proteins, dietary fibers and lipids. These lipids can be broadly characterized as polar lipids and non-polar lipids. The polar lipids are largely made up of glycolipids and phospholipids, and typically they constitute up to about 20 wt % of the total lipid content of an oat oil although the amount can vary a little depending on the oat oil source and how it is obtained. The remaining lipids are non-polar lipids that essentially comprise fatty acids, such as palmitic acid, oleic acid and linoleic acid, as well as some fat-soluble antioxidants.

[0006] The polar lipids found in oat oils are particularly valued for both their nutritional properties as well as their emulsification properties, and are used widely in industrial applications for these reasons, at least.

[0007] Traditionally, polar lipids have been separated from non-polar lipids contained in an oat oil by means of solvent extraction using a non-polar solvent such as hexane. However, this method of separation is not only both tedious and costly, it also suffers from the disadvantage that it is extremely difficult to remove the residues of the solvent employed in the separation process.

[0008] US 8,855,923 describes a process of fractionating oat oils, using various mixtures of polar solvents, water and sugars. This process represents an improvement over extraction methods employing hexane as a solvent. However, depending on how crude is the oat oil starting material, the process of separating lipid fractions can still be rather laborious and costly, and does not result in particularly high yields of polar lipids. There remains a need to provide a cost-effective and facile method of obtaining from an oat oil, a lipid fraction that is enriched in polar lipids, which method can be employed to obtain polar lipid- enriched fractions even when relatively crude and unprocessed oat oils are used as starting materials.

[0009] Summary of the Invention

[0010] In addressing the problems associated with prior art processes, applicant found in a surprising manner that basification of an oat oil starting material before fractionation resulted in improved separation of polar lipid-enriched and non-polar lipid-enriched fractions, and made it possible to recover a polar lipid-enriched fraction with a very high amount of polar lipid in a simple, non- laborious and cost-effective manner.

[0011] Accordingly, the invention provides in a first aspect a method of obtaining a polar lipid-enriched fraction and a non-polar lipid-enriched fraction from an oat oil, the method comprising the steps:

[0012] (a) providing an oat oil containing a mixture of polar lipids and non-polar lipids;

[0013] (b) contacting the oat oil with a polar solvent, water and a base to form a mixture;

[0014] (c) separating the mixture into first and second oil fractions, wherein said first fraction is enriched in polar lipids, and said second fraction is enriched in non-polar lipids; and

[0015] (d) recovering the first fraction and optionally the second fraction.

[0016] In a second aspect the invention provides an oat oil fraction enriched in polar lipids, in particular a fraction obtainable by a method according to the first aspect of the invention.

[0017] In a third aspect the invention provides the use of the oat oil fraction according to the second aspect of the invention as an emulsifier or a nutritional supplement in a consumer product.

[0018] In a fourth aspect the invention provides a consumer product comprising an oat oil fraction according to the second aspect of the invention.

[0019] The details, examples and preferences provided in relation to any one or more of the stated aspects of the present invention will be further described herein and apply equally to all aspects of the present invention. Any combination of embodiments, examples and preferences described herein below in all possible variations thereof are encompassed by the present invention unless otherwise indicated herein, or otherwise clearly contradicted by context.

[0020] In the accompanying Figure 1, there is shown a diagrammatic illustration of a method of separating an oat oil starting material into lipid fractions according to the invention.

[0021] Detailed description of the invention

[0022] The invention in its first aspect is based on the surprising discovery that in a process of fractionating and oat oil using a mixture of polar solvent and water to produce two lipid fractions, the separation of a polar lipid-enriched fraction from a non-polar lipid-enriched fraction was facilitated by the use of a base.

[0023] Without intending to be bound by any particular theory, applicant believes that the use of a base converts polar lipid contained in the oat oil starting material from its zwitterionic form and into its anionic form. The higher polarity of the anionic form decreases the affinity between the polar and the non-polar lipids, leading to their faster and more efficient separation. Furthermore, owing to the efficient separation of the polar and non-polar lipids, the down-stream recovery of the polar lipid- enriched fraction is more straightforward.

[0024] Still further, whereas in the prior art process described in US 8,865,923 the skilled person is taught the importance of controlling the sugar concentration to create separation of the polar and nonpolar lipids fractions, the use of a base in the manner described in the present invention disposes of the need for strict in-process control of sugar concentration, considerably simplifying the process as a result.

[0025] In the process according to the first aspect of the invention, a mixture of polar solvent, water and a base can be added to the oat oil starting material. The order of addition is not particularly critical, but it is preferred if the water and polar solvent are first mixed together with the oat oil before the base is added in order to ensure that the water-solvent oat oil mixture is substantially homogenous before pH adjustment with the base is carried out. This will ensure a more accurate measurement of the change in pH and ensure that not too much base is added than is necessary to effect the required pH change.

[0026] Polar solvents useful in the present invention can be selected from any organic solvent that is miscible with water and is capable of dissolving the non-polar and polar lipids either completely or to some degree. The preferred solvent is ethanol, but other solvents, such as lower alcohols, e.g. methanol or propanol could be used.

[0027] As stated above, fractionation of the oat oil into first and second lipid fractions is achieved using a mixture of polar solvent, water and a base. The separation of the two fractions from each other as well as from solids contained in the oat oil starting material, such as sugars, proteins, starches and any other insoluble residues can be optimized by controlling, in particular, the levels of polar solvent employed in the fractionation step.

[0028] In particular embodiments of the invention, the weight ratio of polar solvent to the oat oil starting material can be controlled to improve the speed and efficiency of separation of polar and non-polar lipid fractions. More particularly, the amount of polar solvent employed can be within the range of about 5 to about 15 wt % based on the total combined weight of polar solvent and oat oil starting material. The polar solvent / water ratio can be within any range such that there is sufficient water in the mixture to enable pH adjustment and measurement. In particular embodiments, the polar solvent / water ratio can be in the range of 70 / 30 to 90 / 10 by weight.

[0029] Regarding the selection of the base, it can be selected from any strong base, and is preferably selected from sodium hydroxide or potassium hydroxide, but most preferably potassium hydroxide.

[0030] The amount of base employed is an amount sufficient to ensure that the polar lipids are converted into their anionic form. This is achieved when the pH of the mixture is adjusted within a range from about 7.0 to 7.5, for example 7.2. It is preferable not to allow increase of the pH above about 7.5 to avoid possible degradation reactions by saponification. The amount of base required to achieve an appropriate pH adjustment and also to limit or avoid the risk of saponification can be achieved by an operator exercising only normal skill and knowledge. By way of example, a level of about 0.1 to about 0.5 wt % of sodium or potassium hydroxide in the polar solvent / water / base mixture is an operative level of base. The pH adjustment can be measured using any convenient state of the art pH-meter, such as a pH-meter SenTix model pH 3110 from Xylem Analytics.

[0031] The mixture is agitated in a suitable mixing tank. Mixing may be carried out using a unidirectional agitator (e.g. Agitator 5.5kW Eex 11 B T3, IP 55). Stirring speed should be sufficiently high and duration of stirring should be sufficiently prolonged to ensure good dispersion of sugars in the oil in order to avoid any risks of solid residues blocking or clogging the apparatus. Typically stirring speeds are in the range 0.5 to 3 m / s, and the duration of stirring is typically in the order of 20 to 40 minutes. This step is typically carried out at ambient temperature.

[0032] At this stage some solid floccules, mainly consisting of sugars and fats, can be observed, and the solid-liquid separation step can be fully effected by centrifugation according to a process more fully described herein below.

[0033] The oat oil useful as a starting material in a process according to the first aspect of the invention can be any of the available forms of oat oil. Oat oils obtained by solvent extraction of oat grains are particularly preferred starting materials.

[0034] A particular advantage of the present invention resides in the fact that fast and efficient fractionation can be achieved regardless of how crude is the oat oil starting material, by which is meant that both relatively crude starting materials as well as relatively processed and pure starting materials can be fractionated in accordance with the method of the present invention. More particularly, the oat oil starting material can be relatively crude oil obtained from a whole meal flour, or it can be a purer form of crude oil obtained from already fractionated material containing high levels of beta-glucans. Still more particularly, oat oils useful as starting materials in accordance with the present invention include a solvent extract, more particularly an ethanolic extract of oat flour, and more particularly the commercially available P14 or P12 oat flour commercially available under the SWEOAT brand.

[0035] The term "polar lipid", as used herein, refers to lipid contained in oat oil that generally comprises phospholipid, glycolipid, sphingolipid or a mixture thereof. The most abundant polar lipids in oat oils are phospholipids, e.g. phosphatidylcholine and N-acylphosphatidyl ethanolamine, and glycolipids, e.g. the galactolipids, mainly monogalactosyldiacylglycerols (MGDG), digalactosyldiacylglycerol (DGDG) and derivatives thereof riGDG, TetraGDG, and various types of estolides.

[0036] The term "non-polar lipid" as used herein, refers to lipid present in oat oil that comprises fatty acids, including palmitic acid, oleic acid and linoleic acid, triacylglycerols, glycerides, or mixtures thereof.

[0037] In oat oils used as a starting materials in the present invention, the lipid content consists of mixtures of both polar and non-polar lipids, with the non-polar lipids representing the overwhelming abundance of lipids present in the mixtures. Typically, the non-polar lipids may represent 70 wt % or more of the total lipids content. The term "enriched" as it is used in relation to oil fractions can be understood in the following way: An oil fraction that is enriched in polar lipids according to the invention, refers to a fraction in which the proportion by weight of polar lipid relative to the non-polar lipid is higher in the fraction than the corresponding proportion in the oat oil starting material from which the fraction is obtained. Similarly, an oil fraction that is enriched in non-polar lipids refers to a fraction in which the proportion by weight of non-polar lipid relative to the polar lipid in that fraction is higher than the proportion in the corresponding oat oil starting material, from which the fraction is obtained. Thus, if in an oat oil starting material contains polar lipids / non-polar lipids in a weight ratio of 30 / 70, then a fraction enriched in polar lipid is any fraction in which that ratio is larger than 30 / 70, for example 40 / 60, although preferably the amount of polar lipid present in such a fraction will be higher than the amount of non-polar lipid present the fraction.

[0038] The method according to the first aspect of the invention provides an efficient means of separating an oat oil into an oil fraction enriched in polar lipids and an oil fraction enriched in non-polar lipids, as well as removing from said oil fractions quantities of other materials contained in the oat oil starting material such as proteins, starches and sugars, thereby to provide oil fractions of high purity and containing higher concentrations of polar lipids than heretofore possible according to prior art methods. In particular embodiments according to the invention an oat oil fraction that is enriched in polar lipids can contain 40 wt % or more of polar lipids.

[0039] The method of carrying out the fractionation of polar lipids and non-polar lipids, as well as preferred embodiments of the method are further described below with reference to Figure 1.

[0040] Referring to Figure 1, in a first step in the method according to the invention an oat oil starting material is dispersed in a mixture of ethanol, water and potassium hydroxide under stirring employing conditions described herein above. During this procedure, the pH of the whole was raised from a pH of about 5 to a pH in the range of 7.0 to 7.5.

[0041] During fractionation the mixture separates into a solid phase and a liquid phase. The solid phase contains insoluble residues including high levels of sugars, proteins and other residues, whereas the liquid phase contains the polar and non-polar lipids.

[0042] The solid and liquid phases can be separated by a suitable method, such as by filtration or centrifugation. In the case of centrifugation, suitable equipment includes a SC 6 unit from GEA Westfalia Separator. The equipment can be pre-rinsed with an appropriate solvent, such as ethanol, to remove water from the inner part of the centrifuge in order to avoid the creation of emulsions.

[0043] The parameters can be determined by a skilled operator to optimize the solid phase exit.

[0044] However, in particular embodiments of the invention, the inlet flow rate can be selected within the range of 50 and 200L / h, and the outlet pressure can be selected in the range of 2 to 3.5 bar. The solid phase is evacuated from the exit during the centrifugation step.

[0045] The liquid phase that is separated from the solid residue is allowed to settle for a period of time sufficient for it to separate into two distinct liquid phases (a so-called heavy phase and a light phase) of sufficiently different density that ensures their distinct separation. Phase separation of the heavy and light phases can be controlled by the selection of the base, solvent and water content employed in the fractionation process as more fully described above. It is a particular characteristic of the present invention that separation of the oil into distinct heavy and light phases occurs readily due to the use of a base in the manner describe herein.

[0046] In particular embodiments of the invention, separation of heavy and light phases can occur in a relatively short period of time, for example 2 hours to 6 hours, which compares very favourably to the much longer settling time required in prior art processes before a sufficiently distinct separation of heavy and light phases occurs. In some cases, prior art process separation times can be as long as 20 hours or more, and still the separation of the two phases may not be particularly distinct.

[0047] Once the heavy and light phases are separated, they each can be subjected to separate work-up procedures to increase their purity. Owing to the facile separation of the light and heavy phases referred to herein above, the subsequent work-up procedure is relatively straightforward compared with prior art processes, which typically requires multiple laborious filtration steps.

[0048] In a work-up procedure the heavy phase, which constitutes the fraction enriched in polar lipids as well as containing residual amounts of sugars and non-polar lipids, is acidified to convert the polar lipids from their anionic form back into their zwitterionic form. Acidification can be carried out using a strong acid, such as hydrochloric acid or phosphoric acid until reaching initial pH of the mixture, that is about pH 5. Acid is added continuously whilst measuring the pH of the system with a suitable pH meter, such as a pH-meter SenTix model pH 3110 from Xylem Analytics.

[0049] The resultant heavy phase can be concentrated, for example by evaporation, distillation, or membrane filtration, thereby to remove any volatile materials, such as solvent residues to recover the oil fraction that is enriched in polar lipids, which fraction forms an additional aspect of the invention as more fully described herein below.

[0050] The light phase, which constitutes an oil fraction enriched in non-polar lipids can be worked-up in the following way: In a first step the light phase is subjected to an acidification step, such as herein above described. Thereafter, the phase is concentrated, again, in a manner substantially as described for the heavy phase. Unlike the heavy phase, the light phase can then be subjected to a solid-liquid separation step to separate salt residues that are present as a result of both the basification and acidification steps thereby to recover an oil fraction that is enriched in non-polar lipids and a low concentration of polar lipids, which oil fraction forms an additional aspect of the invention as more fully described herein below.

[0051] The invention further relates in a second aspect to an oil fraction enriched in polar lipids, and more particular such an oil fraction that is obtainable according to the first aspect of the invention.

[0052] The oil fraction enriched in polar lipids comprises at least 40 wt %, and still more particularly at least 50 wt % of polar lipids, based on the total weight of the oil fraction.

[0053] The third aspect the invention relates to the use of the oil fraction enriched in polar lipids as an additive in consumer products, in particular an emulsifier or nutritional supplement in applications, including food & beverage, perfumery, cosmetic, nutrition and pharmaceutical applications.

[0054] The fourth aspect of the invention relates to consumer products comprising a lipid fraction, and in particular a polar lipid-enriched fraction, as described herein.

[0055] The consumer product includes, but is not limited to, food and beverage, nutritional products, pharmaceuticals, cosmetic and fragrance applications. In particular embodiments the consumer product is a dairy or dairy alternative product including chocolate, non-dairy creamers, vegetable spreads including margarines, ice-cream and all manner of dairy-alternative beverages. The consumer products may also comprise fruits and vegetables, in which case the lipid fractions according to the invention can be applied as a surface coating thereon to act as a preservative.

[0056] In this regard, another aspect of the invention relates to the use of lipid fractions according to the invention as surface-coatings for consumables, such as fruits and vegetables, which can represent a useful improvement over synthetic emulsifiers currently used in the art for this purpose. In consumer product applications the lipid fractions according to the invention may be employed in widely varying levels depending upon the particular application. Operative ranges include but are not limited to 0.1 to about 10 wt % based on the total weight of the consumer product.

[0057] The invention will be further illustrated by reference to the following examples.

[0058] This example is illustrative of the invention.

[0059] The oat oil starting material used in a subsequent fractionation process was produced in the following way: A SWEOAT ™ P14 flour (whole meal oat flour obtained by grinding whole meal oat) was extracted with ethanol 92% (ratio 10L ethanol for 1kg whole meal oat flour). The whole meal flour was twice extracted, performed over 1 hour at 65°C. After filtration and evaporation of the solvent, the oat oil was obtained.

[0060] 6.5 kg of an ethanol / water mixture (80 / 20 by weight) was added to 75 kg of the oat oil raw material produced in the manner described above in an evaporator with a conic bottom (Tournaire skid K1241) and the mixture stirred for 10 minutes at room temperature. The initial pH of the mixture was 4.8, measured with a pH-meter SenTix model pH 3110 from Xylem Analytics.

[0061] 650 g of 48 % potassium hydroxide was added to the mixture under stirring and the resultant mixture was stirred continuously for a further 20 minutes. The pH of the mixture was recorded as 7.2 with a pH-meter SenTix model pH 3110 from Xylem Analytics.

[0062] Thereafter, the mixture was introduced into a centrifuge (GEA Westfalia Separator) at an inlet flow rate of lOOL / hour via a peristaltic pump. The mixture introduced into the centrifuge was recirculated 2 times in a feeding tank until a solid residue separated from the liquid oil phase. The solid residue containing insoluble residues including high levels of sugars and other residues was removed from the centrifuge.

[0063] Thereafter, the oil phase was carefully placed into the evaporator for static decantation for 4h at room temperature. After decantation, two phases were observed: a heavy phase enriched in polar lipids., and a light phase enriched in non-polar lipids. The heavy phase was discharged from the evaporator.

[0064] 10-12% by weight of water was added to the light phase in order to measure a reliable pH value. If water is not added, the phase can be too oily and a reliable pH measurement is more difficult to make. The pH was adjusted to 4.5-5.0, with 40g HCI 18.5%. The light phase was concentrated in the evaporator (65°C, 100 mbar absolute) until ethanol and water are removed from the oily phase. The phase was then filtered on an AF6 plate (6-12 pm) in order to remove salts (potassium chloride).

[0065] Thereafter, the heavy phase was pumped into the evaporator, its pH was adjusted to 4.5-5.0 with 730g HCI 18.5%, and it was then concentrated under the same conditions to remove water and ethanol. The product was then discharged from the evaporator.

[0066] 34.7kg of the light phase (referred to as "PL4") was obtained. This phase contained 1.44 wt % polar lipids.

[0067] 25kg of the heavy phase (referred to as "PL40") was obtained. This phase contained 47.1 wt % polar lipids, which represents 73.8% of the total polar lipids contained in the raw oat oil starting material.

[0068] Example 2

[0069] This example is comparative.

[0070] 6.5 kg of an ethanol / water mixture (80 / 20 by weight) was added to 75 kg of oat oil raw material (prepared in the manner described in Example 1) and the mixture stirred for 10 minutes at room temperature in an evaporator with conic bottom (Tournaire skid K1241). The initial pH of the mixture was 4.8.

[0071] Thereafter, the mixture was subjected to a centrifugation step as set forth in Example 1 above. The oil phase was carefully placed into the evaporator for static decantation for 20h at room temperature. Solid residues were discarded. After 20h decantation, the oil was observed to have separated into two phases: a heavy phase enriched in polar lipids, and a light phase enriched in nonpolar lipids. The heavy phase was discharged from the evaporator.

[0072] The light phase was concentrated in the evaporator (65°C, 100 mbar absolute) until ethanol and water are removed. The product was then discharged from the evaporator and the heavy phase was pumped into the evaporator. It was then concentrated under the same conditions to remove water and ethanol. The product was then discharged from the evaporator.

[0073] The light phase (PL4) was determined to contain 12.56 wt% polar lipids, and the heavy phase (PL40) was determined to contain 34.90 wt% polar lipids.

[0074] Compared to Example 1, the light phase (PL4) contained too much polar lipid, whereas the heavy phase (PL40) was relatively poor in polar lipids, demonstrating a poorer separation between polar and non-polar lipids in the comparative Example. This poorer separation was evident even though the decantation time (20 hours) was five times longer than the decantation time in Example 1. It is posited that this poor separation is the result that without the use of the basification step, the polar lipids remain in zwitterionic form, meaning that the polarity difference between polar lipids and nonpolar lipids is not enough to create a clear separation.

Claims

We Claim:

1. A method of obtaining a polar I ipid-enriched fraction and a non-polar lipid-enriched fraction from an oat oil, the method comprising the steps:(a) providing an oat oil containing a mixture of polar lipids and non-polar lipids;(b) contacting the oat oil with a polar solvent, water and a base to form a mixture;(c) separating the mixture into first and second oil fractions, wherein said first fraction is enriched in polar lipids, and the second fraction is enriched in non-polar lipids; and(d) recovering the first fraction and optionally the second fraction.

2. A method according to claim 1 wherein the polar solvent is ethanol.

3. A method according to claim 1 or claim 2 wherein the ratio ethanol: water is at least 70 parts by weight solvent to 30 parts by weight water.

4. A method according to any of the preceding claims wherein the base is selected from the group consisting of potassium hydroxide or sodium hydroxide.

5. A method according to any of the preceding claims wherein the base is present in the mixture in an amount sufficient to raise the pH of the mixture to about 7 to about 7.5.

6. A method according to any of the preceding claims wherein the oat oil is selected from the group consisting of an extract of an oat flour, and in particular an ethanolic extract of an oat flour.

7. A method according to any of the preceding claims wherein the first oil fraction enriched in polar lipids contains at least 40 wt % of polar lipids based on the total weight of the fraction.

8. A method according to any of the preceding claims wherein the second oil fraction enriched in non-polar lipids contains about 4 wt % or less of polar lipids based on the total weight of the fraction.

9. An oat oil fraction enriched in polar lipids obtainable according to a method according to any of the claims 1 through 8.

10. An oat oil fraction according to claim 9 comprising at least 40 wt % of polar lipids.31207 PCT11. The use of an oat oil fraction according to claim 9 or claim 10 as an emulsifier or a nutritional supplement or a coating in a consumer product.

12. A consumer product comprising an oat oil fraction defined in any of the claims 9 or 10.

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