GAS-IN-OIL-IN-WATER EMULSION AND METHOD FOR ITS PREPARATION

Abstract

The present invention has the objective to provide a stable gas-in-oil-in-water emulsion. Such emulsions can be used as food products, for example as a mayonnaise or salad dressing. This objective has been achieved by a gas-in-oil-in-water emulsion, which is prepared by combining a mixture of sucrose fatty acid ester in water, with an aerated oil containing sucrose fatty acid ester. The aerated oil is dispersed in the aqueous phase, to a product containing oil droplets containing gas bubbles in a continuous aqueous phase. A gas-in-oil-in-water emulsion has been developed which is stable against oil exudation, phase separation and phase inversion for at least two months.

Claims

1. A composition in the form of a gas-in-oil-in-water emulsion, comprising a dispersed phase of oil droplets in a continuous aqueous phase, wherein the oil droplets contain dispersed gas bubbles, and further comprising a sucrose fatty acid ester having an HLB-value ranging from 1 to 7, and wherein the volume fraction of oil droplets containing gas bubbles ranges from 5% to 75% by volume of the composition at standard conditions.

2. A composition according to claim 1, wherein the composition comprises sucrose fatty acid ester having an HLB-value ranging from 1 to 7 as the only isolated emulsifier.

3. A composition according to claim 1, wherein the concentration of sucrose fatty acid ester ranges from 2% to 25% by weight of the composition, preferably from 5% to 15% by weight.

4. A composition according to claim 1, wherein the volume fraction of oil droplets containing gas bubbles ranges from 5% to 60% by volume of the composition at standard conditions.

5. A composition according to claim 1, wherein the volume fraction of gas dispersed in the oil droplets ranges from 2% to 75% by volume of the oil droplets at standard conditions.

6. A composition according to claim 1, wherein the volume fraction of gas dispersed in the oil droplets ranges from 0.5% to 60% of the volume of the composition at standard conditions, preferably from 1% to 50% of the volume of the composition at standard conditions.

7. A composition according to claim 1, wherein at least 90% of the number of oil droplets has a diameter of maximally 400 micrometer, preferably maximally 250 micrometer.

8. A composition according to claim 1, at least 90% of the number of gas bubbles has a diameter of maximally 150 micrometer, preferably maximally 100 micrometer.

9. A method for preparation of a composition according to claim 1, comprising the steps: a) providing a mixture of water and sucrose fatty acid ester having an HLB-value ranging from 1 to 7 at a temperature of at least 60 C.; b) bringing the mixture from step a) to a temperature of less than 60 C., preferably less than 40 C.; c) providing an aerated mixture of an oil and a sucrose fatty acid ester having an HLB value ranging from 1 to 7; and d) dispersing the mixture from step c) into the mixture from step b).

10. A method according to claim 9, wherein in step a) the concentration of sucrose fatty acid ester in water ranges from 5% to 10% by weight.

11. A method according to claim 9, wherein the mixture in step c) is prepared by mixing oil and sucrose fatty acid ester at a temperature of at least 60 C. and aerated by introducing gas into the mixture at a temperature ranging from 60 C. to 95 C.

12. A method according to claim 11, wherein the mixture in step c) is subsequently cooled to a temperature below 60 C., preferably below 40 C.

13. A method according to claim 9, wherein in step d) the mixture from step c) is added to the mixture from step b) under shear, in order to disperse the gas-in-oil phase in the continuous aqueous phase.

14. A method according to claim 9, further comprising the step: e) adding further ingredients to the composition from step d), preferably at a temperature below 40 C., preferably below 30 C., preferably below 25 C.

15. Use of a sucrose fatty acid ester having an HLB-value ranging from 1 to 7, to stabilise a composition in the form of a gas-in-oil-in-water emulsion, comprising a dispersed phase of oil droplets in a continuous aqueous phase, wherein the oil droplets contain dispersed gas bubbles, and wherein the volume fraction of oil droplets containing gas bubbles ranges from 5% to 75% by volume of the composition at standard conditions.

Description

DESCRIPTION OF FIGURES

[0098] FIG. 1: Picture of grid used for determining the Stevens value of gas-in-oil-in-water emulsions as used herein.

[0099] FIG. 2: Two CSLM images of G/O/W-emulsion, sample I from example 2; image size 400400 m. The light coloured irregular shaped items are oil droplets, containing gas bubbles (dark coloured, spherical shape). The oil droplets are dispersed in a continuous aqueous phase (dark coloured).

EXAMPLES

[0100] The following non-limiting examples describe the invention.

Example 1: Materials, Methods, Aerated Oil, Aqueous Phases

[0101] Sunflower oil (SF) ex Cargill (The Netherlands).

[0102] Sucrose ester of mixed fatty acids Ryoto S370 ex Mitsubishi-Kagaku Foods Corporation (Tokyo, Japan). This sucrose fatty acid ester has an HLB of about 3, and contains about 20% mono-ester, and about 80% di-, tri- and polyester.

[0103] Spirit vinegar (12% acetic acid) ex Mizkan (UK).

[0104] Heat-stabilized egg yolk (containing 8% NaCl) ex Bouwhuis Enthoven BV (Raalte, the Netherlands). This is egg yolk which is treated with phospholipase A2.

[0105] Sugar (sucrose) ex Danisco (Denmark).

[0106] Kitchen salt (NaCl) ex Akzo Nobel (The Netherlands).

[0107] Conductivity measurements: are used to determine whether prepared G/O/W-emulsions are water continuous. The equipment used is a portable conductivity meter HI 9835 from Hanna Instruments Inc. (USA). If the electrical conductivity is less than 0.01 mS/cm, the product can be considered to be oil-continuous for all practical purposes. As the aqueous phase contains salt, the conductivity can easily be measured.

[0108] FirmnessStevens value: the Stevens value is determined at 20 C. by using a Stevens LFRA Texture Analyser (ex Brookfield Viscometers Ltd., UK) with a maximum load/measuring range of 1000 grams, and applying a penetration test of 20 mm using a grid, at 2 mm per second penetration rate, with a response weight of 5 g, in a cup having a diameter of 65 mm, that contains the emulsion. The grid has 76 square openings of approximately 33 mm, is made from stainless steel wire with a thickness of approximately 1 mm, and has a diameter of 40 mm. One end of a shaft is connected to the probe of the texture analyser, while the other end is connected to the middle of the grid. The grid is positioned on the flat upper surface of the emulsion in the cup. Upon starting the penetration test, the grid is slowly pushed downward into the emulsion by the texture analyser. The final force exerted on the probe is recorded and translated into the Stevens value in gram. A photograph of the grid is given in FIG. 1.

[0109] Firmness measurements are done 1 hour after production of the emulsion at room temperature, and after storage of the emulsion for 8 weeks at the temperature as indicated in the tables below.

[0110] Syneresis: Syneresis in an oil-in-water emulsion is the expelling of aqueous liquid, which separates from the product during storage after disrupting the structure by e.g. spooning. In this test gravimetric drip of expelled water from an oil-in-water emulsion into an acrylic cylinder is determined during a storage period at various climate conditions.

[0111] Materials: Acrylic cylinder (length 45 mm, inner diameter 21 mm, wall thickness 2 mm, open at two ends) and qualitative filter paper, type 415, diameter 75 mm (ex VWR, Amsterdam, Netherlands). The filter is applied at one end of the cylinder and attached to the outside cylinder wall by adhesive tape. The tube with filter is vertically inserted into an emulsion sample of 225 mL in a jar, until the top of the cylinder is at level with the emulsion surface. The jar is closed with a lid, and stored at 5 C. or 20 C. The amount of liquid in the tube after storage is determined by taking out the liquid from the tube (which has passed through the filter into the tube) with a pipette, and weighing the amount of liquid (in gram) after a determined amount of time. The lower the syneresis value, the better for the stability of the emulsion. Usually measurements are done in duplicate.

[0112] Dynamic viscosity: A flow curve for each sample was made using an Advanced Rheometer AR 2000 (TA Instruments, Great Britain). A smooth, 60 mm diameter stainless steel probe, having a plate-plate geometry with a 1 mm gap was used to obtain viscosity at different shear rates, ranging from 1,000 s.sup.1 to 0.1 s.sup.1 at 25 C. The viscosity of the emulsions was determined 1 hour after preparation, using a shear rate sweep from high to low shear.

[0113] Preparation of Aerated Oil

[0114] Mixtures of S370 emulsifier in sunflower oil (SF) were made, at a concentration of 10% by weight. The blends were kept in aluminium cans overnight in temperature-controlled oven set at 95 C. to ensure that the emulsifier had completely melted, followed by two hours equilibration at 70 C. Subsequently the mixture was aerated by whipping with Kenwood mixer for 4 minutes at maximum speed (relatively high shear). The air content achieved was 74 vol. % (overrun 285%) at standard conditions.

[0115] Preparation of Aqueous Phases

[0116] Four different aqueous phases were prepared, as described in the table below. Ingredients were added to a stirred vessel in the order in which they occur in the table (from top to bottom).

TABLE-US-00002 TABLE 1 Composition of aqueous phase used to prepare gas-in-oil-in-water emulsions. AP1 AP2 AP3 AP4 0% S370 5% S370 with 10% S370 5% S370 no with EY EY with EY EY [wt %] [wt %] [wt %] [wt %] demineralised 78 73 68 77 water sugar 4 4 4 5 S370 0 5 10 5 heat-stabilized 5 5 5 0 egg yolk vinegar 10 10 10 10 salt 3 3 3 3

[0117] S370 was gradually added into the sugar solution in water, while stirring and heated in the water bath until there were no more clumps observed. During cooling in 40 C. water bath, this mixture was stirred every 5 min to prevent the formation of large clumps or crystals of S370.

Example 2: Production of G/O/W-Emulsions without Egg Yolk

[0118] Gas-in-oil-in-water (G/O/W) emulsions containing various level of aerated oil were prepared. Freshly whipped aerated oil from example 1 (at a temperature of about 40-50 C.) was immediately transferred to a Hobart mixer bowl (N50 5-Quart Mixer, Hobart), which already contained the aqueous phase AP4 from example 1 at room temperature. The volume fraction air in the oil was 74 vol. % (overrun 285%). The emulsion was prepared in the Hobart mixer at speed 2 during 1 to 3 minutes (relatively low shear). Hereafter, the mixture was carefully transferred into storage containers with a metal spoon to minimize damage to its structure, and stored at 5 C.

TABLE-US-00003 TABLE 2 Composition (in wt %) of gas-in-oil-in-water emulsions without egg yolk. F G H I J water 38.5 46.2 53.9 61.6 69.3 sugar 2.5 3.0 3.5 4.0 4.5 S370 in aqueous phase 2.5 3.0 3.5 4.0 4.5 vinegar 5.0 6.0 7.0 8.0 9.0 salt 1.5 1.8 2.1 2.4 2.7 sunflower oil 45.0 36.0 27.0 18.0 9.0 S370 in oil phase 5.0 4.0 3.0 2.0 1.0

[0119] The properties of these products are given in the next table.

TABLE-US-00004 TABLE 3 Properties of emulsions from Table 2. F G H I J Volume fraction aqueous phase 21% 28% 38% 51% 70% [vol. %] Volume fraction dispersed phase 79% 72% 62% 49% 30% (gas-in-oil) [vol. %] Volume fraction gas in emulsion 58% 53% 46% 36% 22% [vol. %] Volume fraction oil in emulsion 21% 19% 16% 13% 8% (excl. gas) [vol. %] Electrical conductivity [mS/cm] 0.00 0.15 0.00 8.81 10.02 Overrun of G/O/W emulsion [%] 36 42 40 28 22

[0120] These results show that it is possible to disperse up to at least 50 vol. % oil phase in the aqueous phase containing sucrose fatty acid ester, wherein the oil phase contains gas bubbles at an average gas volume fraction of 74%. The conductivity measurements show that the sample with less than 62% dispersed phase (gas-in-oil) are water-continuous. As an illustrative example, FIG. 2 shows confocal microscopy pictures of the sample I.

Example 3: Preparation of G/O/W-Emulsions with Egg Yolk

[0121] Similarly as in example 2, gas-in-oil-in-water (G/O/W) emulsions containing various levels of aerated oil and stabilized egg yolk were prepared. Freshly whipped aerated oil from example 1 was immediately transferred to a Hobart mixer bowl (N50 5-Quart Mixer, Hobart), which already contained either aqueous phase AP1, AP2, or AP3 from example 1. The volume fraction air in the oil was 74 vol. % (overrun 285%). The emulsion was prepared in a Hobart mixer at speed 2 during 1 to 3 minutes (relatively low shear). Hereafter, the mixture was carefully transferred into storage containers with a metal spoon to minimize damage to its structure, and stored at 5 C. or 25 C. After storage during a specified time period, syneresis, and firmness were determined. The viscosity and conductivity were measured about 1 hour after preparation of the emulsion.

[0122] Table 4, Table 7, and Table 10 show the recipes of gas-in-oil-in-water emulsions that were prepared and in which the oil content, sucrose fatty acid ester content in aqueous phase, and egg yolk content have been varied in a consistent way. These 3 tables form one set of experiments.

TABLE-US-00005 TABLE 4 Recipe (in wt %) of gas-in-oil-in-water emulsions with egg yolk. 1 2 3 4 5 6 7 8 water 61.2 47.6 58.4 70.2 70.2 47.6 47.6 65.7 sugar 3.6 2.8 3.2 3.6 3.6 2.8 2.8 3.6 S370 in 9 7 4 0 0 7 7 4.5 aqueous phase stabilized 4.5 3.5 4 4.5 4.5 3.5 3.5 4.5 egg yolk vinegar 9 7 8 9 9 7 7 9 salt 2.7 2.1 2.4 2.7 2.7 2.1 2.1 2.7 sunflower oil 9 27 18 9 9 27 27 9 S370 in 1 3 2 1 1 3 3 1 oil phase

TABLE-US-00006 TABLE 5 Properties of gas-in-oil-in-water emulsions from Table 4. 1 2 3 4 5 6 7 8 Aqueous phase used [] AP3 AP3 AP2 AP1 AP1 AP3 AP3 AP2 Volume fraction aqueous 58 52 47 80 83 47 41 64 phase [vol. %] Volume fraction dispersed 42 48 53 20 17 53 59 36 phase (gas-in-oil) [vol. %] Volume fraction gas in 35 25 41 11 8.1 33 41 29 emulsion [vol. %] Volume fraction oil in 6.5 22 12 8.9 9.2 20 18 7.1 emulsion (excl. gas) [vol. %] Overrun of emulsion [%] 55 34 71 13 8.8 50 71 40

TABLE-US-00007 TABLE 6 Analytical properties of gas-in-oil-in-water emulsions from Table 4. 1 2 3 4 5 6 7 8 Storage temp. [ C.] 25 25 25 25 5 25 5 5 Syneresis 1 day [%] 0.0 0.7 0.0 66.7 66.7 0.0 0.0 0.7 Syneresis 4 wks [%] 7.3 14.7 16.7 75.3 66.7 8.7 7.3 5.3 Syneresis 8 wks [%] 8.0 18.0 36.7 69.3 66.7 10.0 8.7 5.3 Firmness 1 h [g] 50.0 37.4 17.3 5.9 3.2 50.8 19.6 36.8 Firmness 8 wks [g] 156.8 143 172.2 24.6 8.8 173.2 113.6 141.8 Electrical 0.38 0.28 0.32 0.03 0 0.27 0.24 0.25 conductivity [mS/cm] Viscosity @ 0.1 s.sup.1 3214 10490 623 295 329 13540 5099 9779 [Pa .Math. s] Viscosity @ 500 s.sup.1 0.61 0.54 0.39 0.04 0.02 0.89 0.48 0.76 [Pa.Math.s]

TABLE-US-00008 TABLE 7 Recipe (in wt %) of gas-in-oil-in-water emulsions with egg yolk. 9 10 11 12 13 14 15 16 water 70.2 62.4 51.1 58.9 54.6 61.2 61.2 58.4 sugar 3.6 3.2 2.8 3.2 2.8 3.6 3.6 3.2 S370 in 0 0 3.5 3.5 0 9 9 4 aqueous phase stabilized 4.5 4 3.5 4 3.5 4.5 4.5 4 egg yolk vinegar 9 8 7 8 7 9 9 8 salt 2.7 2.4 2.1 2.4 2.1 2.7 2.7 2.4 sunflower oil 9 18 27 18 27 9 9 18 S370 in 1 2 3 2 3 1 1 2 oil phase

TABLE-US-00009 TABLE 8 Properties of gas-in-oil-in-water emulsions from Table 7. 9 10 11 12 13 14 15 16 Aqueous phase used [] AP1 AP1 AP2 AP2 AP1 AP3 AP3 AP2 Volume fraction aqueous 81 65 40 49 56 56 58 48 phase [vol. %] Volume fraction dispersed 19 35 60 51 44 44 42 52 phase (gas-in-oil) [vol. %] Volume fraction gas in 10 19 43 39 20 38 36 40 emulsion [vol. %] Volume fraction oil in 9.0 16 17 12 24 6.2 6.5 12 emulsion (excl. gas) [vol. %] Overrun of emulsion [%] 12 24 75 65 25 62 55 67

TABLE-US-00010 TABLE 9 Analytical properties of gas-in-oil-in-water emulsions from Table 7. 9 10 11 12 13 14 15 16 Storage temp. [ C.] 25 5 5 25 25 25 5 25 Syneresis 1 day [%] 66.7 36.7 0.0 0.0 13.3 0.0 0.0 0.0 Syneresis 4 wks [%] 73.3 38.7 7.3 17.3 66.7 13.3 6.0 18.0 Syneresis 8 wks [%] 73.3 32.0 8.0 20.0 66.7 15.3 6.7 38.0 Firmness 1 h [g] 6.2 32.4 27.2 26.4 41.4 40.2 37.2 20.4 Firmness 8 wks [g] 40.6 120.4 121.7 203.2 207.8 191 170.5 217.3 Electrical 0 0 0.18 0.22 0.11 0.25 0.34 0.38 conductivity [mS/cm] Viscosity @ 0.1 s.sup.1 440 6269 303 1853 175 4221 4035 1625 [Pa .Math. s] Viscosity @ 500 s.sup.1 0.43 0.40 0.04 0.42 0.06 0.64 0.60 0.47 [Pa .Math. s]

TABLE-US-00011 TABLE 10 Recipe (in wt %) of gas-in-oil-in-water emulsions with egg yolk. 17 18 19 20 21 22 23 24 water 58.4 54.6 54.6 54.6 54.4 58.4 65.7 54.4 sugar 3.2 2.8 2.8 2.8 3.2 3.2 3.6 3.2 S370 in 4 0 0 0 8 4 4.5 8 aqueous phase stabilized 4 3.5 3.5 3.5 4 4 4.5 4 egg yolk vinegar 8 7 7 7 8 8 9 8 salt 2.4 2.1 2.1 2.1 2.4 2.4 2.7 2.4 sunflower oil 18 27 27 27 18 18 9 18 S370 in 2 3 3 3 2 2 1 2 oil phase

TABLE-US-00012 TABLE 11 Properties of gas-in-oil-in-water emulsions from Table 10. 17 18 19 20 21 22 23 24 Aqueous phase used [] AP2 AP1 AP1 AP1 AP3 AP2 AP2 AP3 Volume fraction aqueous 56 61 66 57 59 58 61 62 phase [vol. %] Volume fraction dispersed 44 39 34 43 41 42 39 38 phase (gas-in-oil) [vol. %] Volume fraction gas in 30 13 6.3 19 27 27 33 22 emulsion [vol. %] Volume fraction oil in 14 26 28 24 15 15 6.7 16 emulsion (excl. gas) [vol. %] Overrun of emulsion [%] 43 15 6.7 23 36 37 48 28

TABLE-US-00013 TABLE 12 Properties of gas-in-oil-in-water emulsions from Table 10. 17 18 19 20 21 22 23 24 Storage temp. [ C.] 25 5 5 25 5 5 5 5 Syneresis 1 day [%] 6.7 53.3 48.0 66.7 0.7 2.0 3.3 0.7 Syneresis 4 wks [%] 24.0 56.7 66.7 66.7 7.3 14.0 14.7 6.7 Syneresis 8 wks [%] 24.0 58.0 66.7 66.7 8.0 14.7 18.0 8.0 Firmness 1 h [g] 16.0 20.0 10.0 49.0 28.8 9.2 4.8 43.2 Firmness 8 wks [g] 44.4 45.6 29.8 36.2 106.8 56.4 39 116.2 Electrical conductivity 0.29 0.03 0.06 0.12 0.3 0.35 0.61 0.47 [mS/cm] Viscosity @ 0.1 s.sup.1 4310 150 117 285 3673 1220 80 5140 [Pa .Math. s] Viscosity @ 500 s.sup.1 0.20 0.02 0.09 0.09 0.43 0.16 0.12 0.49 [Pa .Math. s]

[0123] The compositions containing aqueous phase AP1 (emulsions 4, 5, 9, 10, 13, 18, 19, 20) did not yield satisfactory results. These samples have a high syneresis, low viscosity, and low firmness. The presence of the sucrose fatty acid ester is required to disperse the aerated oil phase.

[0124] The emulsions prepared with aqueous phases AP2 and AP3 (5% or 10% sucrose fatty acid ester in the aqueous phase) show that gas-in-oil-in water emulsions containing up to at least 60 vol. % dispersed phase (gas-in-oil) could successfully be prepared. The presence of egg yolk helps to be able to disperse higher amounts of oil as compared to emulsions without egg yolk in example 2. The emulsions containing 10% sucrose fatty acid ester in the aqueous phase are more stable than the emulsions containing 5% sucrose fatty acid ester in the aqueous phase, as shown by lower syneresis values.

[0125] The storage temperature (5 or 25 C.) did not have a large influence on the structure of the emulsions. For example emulsions 14 and 15 have the same composition and are stored at 5 and 25 C. respectively. The firmness of these two samples does not differ dramatically. Syneresis is improved when stored at 5 C.