WO1997010050A1

WO1997010050A1 - Surface-active composition

Info

Publication number: WO1997010050A1
Application number: PCT/EP1996/003930
Authority: WO
Inventors: Jan Benjamins; Karel Abraham Kuypers; Emmie Helena Lucassen-Reynders
Original assignee: Unilever NV
Current assignee: Unilever NV
Priority date: 1995-09-14
Filing date: 1996-09-09
Publication date: 1997-03-20
Anticipated expiration: 1998-03-14
Also published as: ZA967707B; AU6987996A

Abstract

Extraction of oats yields an acetone soluble composition possessing strong W/O emulsifier properties.

Description

SURFACE-ACTIVE COMPOSITION

The present invention relates to a new, natural surface- active composition, in particular for use as an emulsifier and/or foaming agent in food products and to methods for preparing the same.

BACKGROUND OF THE INVENTION

The demand for natural, so called "green", ingredients, including emulsifiers, for use in food products is increasing. In this context "natural" means "originating from a natural source", such as plants.

Two types of emulsifiers exist: water-in-oil (W/O) emulsions require oil-soluble or lipophilic emulsifiers, whereas oil-in-water (O/W) emulsions need water-soluble emulsifiers. The latter emulsifiers are quite abundantly available from natural sources, but natural lipophilic emulsifiers are far less widespread.

Saturated and unsaturated monoglycerides are established W/O emulsifiers. These can stabilize fairly dilute emulsions but not concentrated emulsions. A dilute emulsion is an emulsion with relatively little disperse phase, like margarine, which is a water-in-oil emulsion containing only about 16% water. Concentrated emulsions have a large disperse phase content, such as the low fat spreads which contain 40% water or more. Other common lipophilic emulsifiers are polyglycerol polyricinoleate esters, also known under the brandname Admul WO ™ (E476) , which is very effective in stabilizing concentrated water-in-oil emulsions. The major drawback of Admul WOL™ is that it is not considered natural.

Oat oil is produced by extraction of oats with a food permitted extraction liquid, preferably an aliphatic alcohol, particularly isopropanol. Oat oil contains oat glycolipids. When oat oil is subjected to an extraction with methanol an oily substance with surface activity remains after evaporation of the methanol, as described by Evans et al . in European Patent Application 0 371 601. Alternatively, said oily substance with surface activity may be obtained in one step from oats employing an extraction with supercritical carbon dioxide and evaporating the extraction liquid, a technique described in Stahl, E., Quirin, K.-W., Gerard, D., Verdichtete Gase zur Extraktion und Raf filiation, Springer Verlag, Berlin, 1988.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a new surface-active composition exhibiting an emulsifying activity comparable to Admul WOL™ but of natural origin.

It has been found that an acetone soluble fraction isolated from cereals, shows a surprising emulsifying activity.

The invention thus relates to a surface-active, acetone soluble composition obtainable by solvent extraction from cereals. The composition may be obtained by a process comprising extracting cereals, preferably oats, as source material using successive extraction steps and employing as extraction liquids A. one or more polar extraction liquids,

B. acetone or an acetone substitute which is able to extract acetone soluble components, where the extractions may be applied in any order, first on the cereals and subsequently on the residue of the preceding extraction.

Besides a process for preparation of the above composition, the invention comprises the use of such composition as emulsifier and foaming agent, and foods in which such composition has been incorporated.

DETAILS OF THE INVENTION

The process of the invention is applicable on cereals in general, but, preferably, oats are used as source material. According to the aforementioned European patent application 0 371 601 an emulsifying substance is isolated from oat oil, by treating the oily substance left after drying the methanol extract with a proper extraction liquid, particularly acetone.

Said reference tells to employ the acetone-insoluble material of the extraction as emulsifier, which like Admul WOL™ (76 wt.% of hydroxy fatty acids) is characterized by a considerable amount of hydroxy fatty acids, while the acetone washings remain undiscussed. The present invention is based on the surprising finding that it is the acetone- soluble material of the methanol extract (containing little hydroxy fatty acids) which has superior surface activity and shows excellent emulsifying properties. The invention comprises the use of any extracting liquid which can substitute acetone in the extraction process, such as mixtures of methanol and dichloromethane, as far as its enables the extraction of the acetone soluble fraction which is essential for the surface activity.

The acetone extraction usually follows the initial extraction of cereals consisting of one or more successive extractions with a polar extraction liquid, but it may also be the initial cereals extraction step.

Depending on the sequence of extractions the acetone soluble part may be accompagnied by different other substances .

Preferred polar extraction liquids are aliphatic alcohols, more preferably methanol and isopropanol, and supercritical carbon dioxide.

The main component of the found surface-active composition has been identified as digalactosyl diglyceride (DGDG) . The invention comprises acetone soluble, surface active compositions, obtainable by solvent extraction containing at least 50 wt.% DGDG and, preferably, containing at least 70 wt.% DGDG. Other co-extracted components possibly are fatty acid esters of sterol glucoside, hexose glycerides and glycophospholipids . Each individual component does not show substantial emulsifying activity when used separately, but compositions containing two or more of them are very effective as emulsifier.

Until now Admul WOL™ was considered to be an unsurpassed emulsifier for low calorie oil (emulsion of 70% water-in- oil) , low fat salad dressing, low fat cheese (a duplex emulsion of water-in-oil-in-water) and low fat spreads with a high amount (at least 60 wt.%) of dispersed water. The invented emulsifier is powerful enough to stabilize even concentrated water-in-oil emulsions. The acetone soluble surface active substance was found to equal and in specific cases even to surpass Admul WOL as a stabiliser of 40 wt.% fat W/O emulsions.

Consequently, the invention comprises use of the found surface-active composition as defined hereinbefore as an emulsifier, particularly as a lipophilic emulsifier for preparing water-in-oil emulsions and more particularly as a lipophilic emulsifier in low fat products, preferably products selected from the group consisting of low fat cheese, low fat spread, very low fat spread, low calorie oil and low fat salad dressing.

The invention comprises too food compositions in which a surfactant composition as defined hereinbefore has been incorporated, preferably when the food composition is an emulsion or a bakery product. Food compositions preferably contain a maximum of 30 wt.% of fat, more preferably a maximum of 20 wt.% of fat, still more preferably a maximum of 13 wt.% of fat.

According to a further embodiment the found composition is used as a foaming agent, suitable in bread making processes.

The present invention will be illustrated by the following examples:

EXAMPLE 1

Preparation of an emulsifier composition from oats

Oat oil was prepared according to the procedure as described in several references (Forssel et al. , Fat Sci. Technol . 94, 335 (1992) ; Jayasinghe et al . , J. Dispersion Sci. Techn. 12, 443 (1991) ; PCT/GB88/00321; and EP-0 371 601) . One kg of rolled oats was stirred with 2.5 1 of isopropanol at 75°C for 2.5 h. The liquid was decanted and left overnight at room temperature for any solid residue to settle. After filtration of the almost clear supernatant and evaporation of the isopropanol, 75 ml of an oily residue (oat oil) was obtained. This oil, which contained some undissolved material, was extracted with 300 ml of methanol for 5 h at room temperature, resulting in a three- layer system. The bottom layer, which had an oily appearance, and the emulsion-like middle layer were discarded. From the top layer the methanol was evaporated yielding 13.5 g of viscous lipids of partly crystalline appearance. This residue, denoted as IPA/MeOH extract, is equivalent to NEFO, the "natural emulsifier from oats", known from PCT/GB88/00321 and EP 0 371 601. It contained 25 wt.% of phospholipids.

This IPA/MeOH extract was extracted with acetone. The residue left after evaporation of the acetone (IPA, MeOH, acetone extract = "OAT 1") exhibited strong surface activity.

EXAMPLE 2 Assessment of emulsifying activity

The emulsifying activity of surface active substances, including the one obtained according to example 1, was determined as follows: a dispersion of 40 vol .% of water in oil was prepared, containing 1 wt.% of emulsifier, which was either the IPA/MeOH extract or the IPA/MeOH/Acetone extract or Admul WOL™ or Dimodan LS™. According to Lucassen-Reynders & Kuijpers, Colloids & Surfaces 6_5, 175 (1992)) the drop size of the resulting emulsion, both initially and after one day was measured. These values indicate the emulsifier and stabilizer performance. Emulsifier performance is measured by the initial drop size, while stabilization appears from the slow increase of average drop size in a quiescent emulsion during one day. Both the original IPA/MeOH extract and the IPA/MeOH/acetone extract appeared to be soluble in sunflower oil

TABLE I

Drop size of 40% W/O emulsions

Emulsifier (1) D₀ (μm) (2) D, (μm) (3)

OAT EXTRACTS

IPA/MeOH extract 20 40

IPA/MeOH/Acetone 9 14 extract (OAT 1)

COMMERCIAL EMULSIFIERS

Admul WOL™ 8 10

Dimodan LS™ 20 > 1000

(1) 1 wt.% in oil phase. (2) initial average drop size

(3) average drop size after one day

From Table I it appears that emulsions containing the IPA/MeOH/Acetone extract appeared to be reasonably fine and stable, equalling Admul WOL™ in performance.

EXAMPLE 3 Characterization of fractions of oat oil fractionating

Using analytical techniques such as Thin Layer Chromatography (TLC) , HPLC, NMR, and a FAME GC test for determining the content of hydroxy fatty acids, the surface active priciple isolated according to example 1 was found to contain at least four components, of which one was identified as digalactosyl diglyceride (DGDG) . The other three components produced TLC spots located between the reference substances monogalactosyl diglyceride (MGDG) and DGDG. These were believed to be a sterol glucoside fatty acid ester, a hexose glyceride other than DGDG and a glycophospholipid. Analysis of the fatty acids composition showed that mainly C18 (78%) and C16 (16%) fatty acids were present, on average containing 1.3 double bond per chain. The content of hydroxy fatty acids was found to be very low (<3.5%) . Admul WOL™ and the insoluble residue of the acetone extraction as referred to in EP 0 371 601 are reported to contain a high amount of hydroxy fatty acids, Admul WOL™: 76 wt.% on total fatty acid content.

EXAMPLE 4 Emulsified spread products

A two-kg sample of a 40 wt.% fat spread was prepared, employing a Votator consisting of two surface scraped heat exchangers and a pin stirrer, using as ingredients

756 g regular fat blend

4 g emulsifier (0.2 wt.% on product) 4 g β-carotene 1120 g water 20 g whey powder

50 g gelatin 8 g sodium chloride 2 g potassium sorbate

As emulsifiers were used Admul WOL™ and "OAT 1". The ingredients were combined into a water continuous pre- emulsion of 45°C and were subjected to common inversion processing in a Votator system. The "OAT 1" containing spread showed good spreadability, possessed acceptable oral melt and a water distribution which was even better than the Admul WOL™ containing spread, which exhibited some free water.

Claims

1. Surface-active, acetone soluble composition obtainable by solvent extraction from cereals, preferably oats.

2. Composition according to claim 1 which contains at least 50 wt.% of digalactosyl diglyceride, preferably at least 70 wt.% digalactosyl diglyceride.

3. Composition according to claims 1 or 2, characterized in that the extraction solvents are at least acetone and additionally one or more solvents chosen from the group consisting of aliphatic alcohols, preferably isopropanol, and supercritical carbon dioxide.

4. Composition according to claim 1, characterized in that it is obtainable by a process comprising the steps a. extracting first cereals with a polar extraction liquid, b. evaporating the extraction liquid to obtain a surface-active residue, c. leaching and collecting the acetone soluble part of the residue of the previous step.

5. Composition according to one of the previous claims, characterized in that isopropanol, methanol and acetone are used as extraction liquids, where each extract is dried and the residue is subjected to the next extraction step.

6. Composition according to any one of claims 1-4, characterized in that supercritical carbon dioxide and acetone are used as extraction liquids, where each extract is dried and the residue is subjected to the next extraction step.

7. Process for the preparation of a surface-active, acetone-soluble composition, comprising extracting cereals, preferably oats as source material using successive extraction steps and employing as extraction liquids a. one or more polar extraction liquids, b. acetone or an acetone substitute which is able to extract acetone soluble components, where the extractions may be applied in any order first on the cereals and subsequently on the residue of the preceding extraction.

8. Process according to claim 7, characterized in that the extraction liquids are at least acetone and additionally one or more solvents chosen from the group consisting of aliphatic alcohols, preferably isopropanol, and supercritical carbon dioxide.

9. Process according to claim 8, characterized in that after drying the isopropanol extract the residue is extracted with methanol, followed by evaporation of the methanol and subjecting the residue of the methanol extract to acetone extraction after which the acetone soluble part is collected.

10. Use of a surface-active composition as defined in or prepared according to any one of the preceding claims as a foaming agent.

11. Use of a surface-active composition as defined in or prepared according to any one of the preceding claims as a lipophilic emulsifier for preparing water-in-oil emulsions.

12. Use of a surface-active composition as defined in or prepared according to any one of the preceding claims as a lipophilic emulsifier in low fat products, preferably selected from the group consisting of low fat cheese, low fat spread, very low fat spread, low calorie oil and low fat salad dressing.

13. Use of a surface-active composition as defined in or prepared according to any one of the preceding claims in bread making.

14. Food composition in which a surfactant composition as defined in or prepared according to any one of the preceding claims has been incorporated.

15. Food composition as claimed in claim 14, which is an emulsion or a bakery product.

16. Food composition as claimed in claims 14 or 15, which is a low fat product comprising a maximum of 30 wt.% of fat, preferably a maximum of 20 wt.% of fat, more preferably a maximum of 13 wt.% of fat.