OA20204A - Process for preparing fat continuous emulsions. - Google Patents

Abstract

A process for preparing a water-in-oil emulsion which emulsion comprises oil and a hardstock fraction next to an aqueous phase. The process involves blending the melted hardstock fraction with a water-continuous dispersion comprising part or ail of the oil and part or ail of the aqueous phase and with a fat-continuous dispersion comprising the remainder of the oil and the remainder of the aqueous phase. The combined stream is mixed by a high shear mixer with short residence time.

Description

PROCESS FOR PREPARING FAT CONTINUOUS EMULSIONS

Field of invention

The présent invention relates to a process for preparing fat-continuous émulsions (such as e.g. spreads and margarines) which émulsions comprise fat components like oil and hardstock fat (also known as structuring fat, or simply: “hardstock”) and a dispersed aqueous phase. The process easily allows reworking of any waste streams from spreads production.

Background of invention

Edible water-in-oil émulsions, which comprise a continuous fat phase and a dispersed aqueous phase, are well known in the art and include for example margarine.

The fat phase of margarine and similar water-in-oil émulsions is typically a mixture of liquid oil (i.e. fat that is liquid at ambient température) and fat which is solid at ambient températures. The solid fat, also called structuring fat or hardstock fat, serves to structure the fat phase and helps to stabilize the aqueous phase (e.g. in the form of droplets) by forming a fat crystal network. Ideally the structuring fat has such properties that it melts or dissolves at mouth température otherwise the product may hâve a heavy and/or waxy mouthfeel.

Margarine is generally defined as a composition containing at least 80 wt. % fat and about 20 wt. % aqueous phase. In contrast, (spreadable) émulsions containing less than 80 wt. % fat are generally called spreads. Nowadays the terms margarine and spread are sometimes used interchangeably although in some countries the commercial use of the term margarine is subject to certain regulatory requirements.

In the market place margarine is generally sold as one of three principal types of waterin-oil émulsion:

• hard or stick margarine (also referred to as wrappers);

• (typically softer) tub margarine (typically named “spreads)”; and • liquid or pourable margarine.

Wrapper margarines and tub margarines are non-pourable and generally contain a higher amount of hardstock fat than liquid or pourable margarines.

The general process for the manufacture of water-in-oil émulsions, using the votator or churn process, encompasses the following steps:

1. Mixing of the liquid oil, the hardstock fat and the water-phase at a température at which the hardstock fat is definitely liquid;

2. cooling of the mixture under high shear to induce crystallization of the hardstock fat to create an émulsion;

3. formation of a fat crystal network to stabilize the resulting émulsion and give the product some degree of firmness;

4. modification of the crystal network to produce the desired firmness, confer plasticity and reduce the water droplet size.

These steps are usually conducted in a process that involves apparatus that allow heating, cooling and mechanical working of the ingrédients, such as the churn process or the votator process. The churn process and the votator process are described in the Ullmans Encyclopedia, Fifth Edition, Volume A 16, pages 156-158. A disadvantage of such process is that it requires heating up and cooling the whole formulation, e.g. including ail oil and ail water. This costs a lot of energy.

An alternative to the votator or churn process for the manufacture of margarines which is known involves the use of fat powder comprising hardstock fat (i.e. pre-crystallized fat) (WO 2005/014158). The fat powder used in such process is also known as ScMM powder (super critical melt micronisation) or PGSS process (particles from gas saturated solutions). Spreads can be made by blending at ambient or colder température liquid oil, the fat powder and an aqueous phase. This overcomes having to heat and cool the entire formulation and thus reduces energy consumption when compared to the votator process. Disadvantages of such process relate e.g. to the need for equipment which is new in margarine and spreads making (pressurizing and handling CO₂, spraying melted fat, handling fat powder) and capital expenditure. Also, reworking of finished product which cannot be packaged is possible, but not straightforward.

An easy possibility for reworking is desired in any margarine or spreads manufacturing, as packaging lines are prone to breakdown. In case of such breakdown, the spreads processing line usually cannot be stopped immediately, as such may lead to clogging of lines, pumps and mixers, or products which are excessively worked due to continued stay in shear equipment which may lead to build up of heat and/or détérioration ofthe structure. For this reason, easy re-working of manufactured product which cannot immediately be packed is desired, as otherwise it may lead to high volumes of waste material. Reworking in a votator line is comparatively easy as the composition in the mixing tank feeding the first scarped surface heat exchanger has the same net composition as the finished product. The finished product just needs to be heated up to melt and it can be added to the first mixing tank. An example is set out in US 6322843. Reworking for the ScMM process has been described in WO 2015/052026.

A further alternative for making spreads is known e.g. from GB1327511. This reference discloses a process for the préparation of low-calorie spreads by mixing a first liquid (which is at a température of at least 28°C) which consists of a fat phase containing crystallisable material with a second liquid (which is at a température of at most 8°C) which is substantially free from crystallisable material. At least part of the second liquid is composed ofthe aqueous phase, and may further contain oils which are liquid at 2°C. The two liquids are fed separately to a high pressure dosing pump, allowing continuous dosing of both liquids to an emulsifying apparatus and subsequently fed to a working unit.

US 3472661 discloses a process for preparing liquid margarines, by a process in which a liquid vegetable oil is blended with a thickening agent (a high melting fat), an emulsifier and a phosphatide, and chilling the blend to a point at which it partially crystallises, followed by holding for at least five hours and then vigorously agitating the blend to obtain a uniform dispersion ofthe fat crystals. The aqueous phase is then added to the fat phase.

There is a desire for a process that allows the manufacture of fat-continuous émulsions comprising edible oil and hardstock (or structuring fat), and which process does not require heating up and cooling of the entire formulation (for reasons of energy consumption) as is required for making such with the known votator process, and which process does not need complex equipment such as is e.g. needed for making the fat powder using the PGSS process, yet which allows for reworking of manufactured product.

Summary of the invention

It was found that these objectives can be met, at least in part, by a process for preparing a fat-continuous émulsion, which émulsion comprises 15-83% of an aqueous phase and 17-85% of a fat phase, said fat phase comprising 10-100 % hardstock fat (weight % on total fat phase), and 0-90%% oil (weight % on total fat phase), which process comprises the steps of:

a. providing a water-continuous dispersion at a température of between 0°C and 15°C comprising part ofthe aqueous phase as the continuous phase with dispersed therein part ofthe oil;

b. providing part of hardstock fat in melted form and at a température of between 30°C and 60°C;

c. providing a fat-continuous dispersion which comprises the remainder of the aqueous phase, the remainder of the oil, and the remainder of the hardstock, which dispersion comprises fat crystals in an amount of from 0.2 to 10% by weight, based on the total dispersion provided by this step c.;

d. combining the water-continuous dispersion of step a. with the melted hardstock fat of step b. and the fat-continuous dispersion of step c, wherein the weight ratio of water-continuous dispersion + melted hardstock : fat-continuous dispersion is from 100 : 1 to 5 : 1 ;

e. subjecting the mixture obtained after step d. to a high shear device to provide a fat-continuous émulsion;

wherein the température of the mixture obtained from step d. is below the melting point of the hardstock fat.

Detailed description ofthe invention “Hardstock” (“hardstock” and “hardstock fat” and “hardstock phase” herein hâve the same meaning) is herein to be understood to be an edible fat that is solid at ambient température as understood by the person skilled in the art.

It was surprisingly found that by the process of the présent invention, that if the dispersion obtained from step c. and combined in step d. with the streams of step a. and step b. contâined a minimum of fat crystals (or fat in crystallised form) an improved product quality could be obtained, when compared to a process in which the dispersion in step c. (when added in step d. to the streams of step a. and b.). The improvement in product quality can be e.g. in smaller water droplet size of the final product, or a better stability (sometimes even after température cycling). Following this, the dispersion obtained by the process step c., prior to combining with the other components in step d., should contain fat crystals in an amount of at least 0.2% by weight, based on the total dispersion provided by this step c. More fat crystals being présent can be désirable, but a very high amount could lead to practical limitations, in the sense that the dispersion will be more difficult to handle, e.g. more difficult to pump. Thus, the dispersion obtained by the process step c., prior to combining with the other components in step d., should contain fat crystals. Preferably, the dispersion in step c. (prior to step d) comprises fat crystals in an amount of from 0.2 to 10% by weight, based on the total dispersion provided by this step c. More preferably, the dispersion in step c. (prior to step d) comprises fat crystals in an amount of from 0.4 to 7% by weight, based on the total dispersion provided by this step c.

The amount of the fat crystals in the dispersion of step c. as above referred to can be controlled e.g. by controlling the température of this dispersion, e.g. in a holding tank or in a continuous way by e.g. a heat exchanger. It is preferred in this connection that the fat-continuous dispersion in step d. is at a température of between 20 and 50°C prior to combining with the dispersion of step a. and the hardstock of step b.

The water-continuous dispersion of step a. can be prepared in any suitable manner. It can be prepared both in a continuous and in a batch-like process, and whichever is preferred dépends very much on the logistics and available equipment in the factory. Hence, it may be preferred that in the process according to the présent invention the water-continuous dispersion of step a. is obtained by mixing continuously in-line an aqueous phase at a température of from 0 to 15°C (more preferably 2-12°C) with oil at a température of from 0 to 25°C (more preferably 5-20°C).ln the alternative, it may be referred that in the process according to the présent invention the water-continuous dispersion of step a. is obtained by providing a stirred tank comprising oil dispersed in the aqueous phase, which stirred tank is held at a température of from 0 to 15°C (more preferably from 2 to 12°C) for at least 30 minutes, more preferably at least 45 minutes).

The fat-continuous dispersion in step c. can in principle hâve any amounts of oil, hardstock fat, and aqueous phase, as long as it is a fat-continuous dispersion having the specified level of fat crystals. However, it is preferred that this dispersion in step c. comprises, or even more preferably is, the rework stream ofthe product obtained after step e, optionally after further mixing, as this is a huge benefit, as it easily and conveniently allows rework of any of the émulsion produced by the process of the invention, e.g. if the packaging line is broken down. For this reason it is preferred that the fat-continuous dispersion in step c. is at a température of between 20 and 50°C prior to combining with the dispersion of step a. and the hardstock of step b in step d. The actual température needed to comply with the need for 0.5-5% fat crystals dépends e.g. on the types of hardstock fat and oil, the overall composition, but can easily be determined by the skilled person with routine expérimentation: trying a few températures and measuring the amount of fat crystals to make sure it is within the claimed range.

In order for sufficient hardstock crystals to be formed during or shortly after the high shear mixing operation, it is preferred that the température of the water-continuous dispersion in step a. is between 0 and 10°C, more preferably between 2 and 8°C. For the same reason the hardstock fat should be ail melted, yet not be at a very high température. In this connection, it is preferred that the température ofthe melted hardstock in step b. is between 30 and 45°C, more preferably such température is between 32 and 40°C.

As to the amount the water-continuous dispersion of step a. being combined in step d. with the melted hardstock fat of step b. and the fat-continuous dispersion of step c, it is clear that, within reasonable ranges, the more of the dispersion of step c. (with the fat crystals) is added to the streams obtained by step a. and b., in step d, the more the benefits would be obtainable. In other words, a fairly high amount of reworking can be bénéficiai, in the présent invention. However, the rework steram of step c. should not be too high to become unpractical. Hence, in the présent invention, the watercontinuous dispersion of step a. is preferably combined in step d. with the melted hardstock fat of step b. and the fat-continuous dispersion of step c, such that the weight ratio of water-continuous dispersion + melted hardstock : fat-continuous dispersion is from 40 : 1 to 10 : 1.

As to the amount of hardstock to be used, a middle ground should be found between low SAFA (saturated fatty acid) levels, stability, and practical workability. Following this, it is preferred that the weight ratio of water-continuous dispersion + melted hardstock : fat-continuous dispersion in the process is from 40 : 1 to 10 : 1. Likewise, the the weight ratio of oil : hardstock in the product as made by the process of the présent invention is preferably from 1 : 0.1 to 1 : 1.

Preferably, for reasons of consumer acceptance and the image of being ail natural, the hardstock fat comprises at least 70% (more preferably at least 80%) of triglycéride esters of fatty acids (TAG’s), by weight based on the total hardstock fat.

As to step e., the subjecting of the mixture of ail ingrédients obtained to high shear mixing, this mixing step e. is preferably carried out in a continuous process. In order to achieve the desired phase inversion ofthe aqueous dispersion into a fat-continuous émulsion with water droplets of the desired size and the formation of small crystals of hardstock that can stabilise such émulsion and that can give sufficient firmness to the product, the mixing of the combination of water-continuous dispersion with melted hardstock and fat-continuous dispersion should go in a swift way, and also the mixing operation should only resuit in a small température increase due to such high shear mixing. Regarding the latter, it is preferred that the high shear device results in a température increase of the émulsion of less than 5°C, more preferably a température increase ofthe émulsion of less than 3°C, when comparing température ofthe aqueous dispersion at the inlet and the température of the émulsion at the outlet of the high shear device. It was found that a high shear mixer having a rotor and a stator, which mixer has a résidence time of less than 3 seconds, and sufficient shear to effect émulsification of water droplets in oil having a droplet size D₃₃ of less than 15 micrometer, can achieve such objectives. Hence, preferably the high shear device in step e. is such high shear mixer. A typical example of a mixer that can achieve the desired objectives is a fluid division mixer (FDM) as marketed by Maelstrom and as is described e.g. in EP1331988, in WO2002/38263, and in WO2013/037605.

Following the above, in the process according to the présent invention, in view of the above considérations, the high shear device in step e. is preferably a high shear mixer having a rotor and a stator, which mixer has a résidence time of less than 3 seconds, and sufficient shearto effect émulsification of water droplets in oil having a droplet size

D3.3 of less than 15 micrometer.

Depending on the product mixture (e.g. presence of protein) it may be desired to subject the mixture that is obtained in step d. from the high shear device to a pin stirrer (in other words: to add a pin-stirrer after the process as set out above). Pin stirrers are also known in margarine processing as C-units. Thus, it may be preferred that subjecting the mixture in step e. to a high shear device is followed by subjecting the mixture to a pin stirrer.

Although the process according to the présent invention may yield liquid products or wrapper-type margarines, it is preferred that the fat continuous émulsion made by this process is a spreadable émulsion. A spreadable émulsion is an émulsion of the composition as described herein, which furthermore has a Stevens value of between 30 and 300 gram, when measured at 5°C.

The process according to the présent invention may be carried out on compositions with different fat levels. It is preferred, for économie reasons, that the composition comprises 40-80% fat.

In order to manage the final composition of the product, it may be preferred that the overail composition ofthe fat-continuous dispersion of step c. is the same as the overail composition ofthe fat-continuous émulsion produced by step e.

Examples

Methods

Water droplet size distribution of W/O émulsions

The normal terminology for Nuclear Magnetic Résonance (NMR) is used throughout this method. On the basis of this method the parameters d₃,₃ and exp(o) of a lognormal water droplet size distribution can be determined. The d_3i3 is the volume weighted mean droplet diameter (in microns, in the présent case) and e^CT (e-sigma) is the standard déviation of the logarithm ofthe droplet diameter.

The NMR signal (écho height) ofthe protons of the water in a water -in-oil émulsion are measured using a sequence of 4 radio frequency puises in the presence (écho height E) and absence (écho height E*) of two magnetic field gradient puises as a function ofthe gradient power. The oil protons are suppressed in the first part ofthe sequence by a relaxation filter. The ratio (R=E/E*) reflects the extent of restriction of the translational mobility ofthe water molécules in the water droplets and thereby is a measure of the water droplet size. By a mathematical procedure -which uses the lognormal droplet size distribution - the parameters ofthe water droplet size distribution d_{3 3} (volume weighed géométrie mean diameter) and σ (distribution width) are calculated.

A Bruker magnet with a field of 0.47 Tesla (20 MHz proton frequency) with an air gap of 25 mm is used (NMR Spectrometer Bruker Minispec MQ20 Grad, ex Bruker Optik GmbH, DE).

Solids in rework stream

The amount of solids in the rework stream in the examples was measured with NMR

Examples 1, 2

A spreadable edible émulsion was prepared having the recipe as in Table 1.

Table 1

Component	Amount (wt % on total)	Phase
Palm oil	31	Hardstock phase
Rapeseed oil	22.8	Emulsion phase
PO58	5	Hardstock phase
MonoGlyceride (Emulsifier)	0.6	Hardstock phase
Lecithine	0.1	Hardstock phase
b-carotene (30% solution)	0.138	Emulsion phase
Demi-water	38	Emulsion phase

Sait	1.6	Emulsion phase
Petassium sorbate	015	Emulsion phase
skimmed milk powder	0.5	Emulsion phase
NaCaEDTA	0.0058	Emulsion phase
Lecithine	0.1	Emulsion phase

The composition was made by first preparing the émulsion phase in a premix vessel. The émulsion phase so-prepared was kept at 6°C.

The hardstock phase was made by mixing ail ingrédients for this phase in a second premix vessel.

The émulsion phase was then mixed in-line with the hardstock phase and subsequently in-line with the rework phase in a ratio of 33:57:10.

The hardstock phase température at the point of mixing was 44°C, the waterphase at 6°C. The rework phase had the same composition as the combined émulsion and hardstock phase. The température ofthe rework phase was 40°C (example 1) and 50°C (example 2).

The combined stream was fed to a high shear mixer (operating at 2800 rpm). This mixer was ofthe type FDM or fluid division mixer by Maelstrom, similar as in WO 02/38263, with a concentric rotor-stator system with 4 rows of cavities in both rotor and stator, with a total volume of 0.083 liter. The cavities in the rotor and stator of the FDM, were spherical segments which are open on both vertical and horizontal faces. The rotor and stator are based on a stepped conical form so that the diameter of the cône increases from inlet to outlet (about 50 up to 150 mm). The mixer is commercially available from Maelstrom (http://www.maelstrom-apt.com/product-dc50/).

This high shear operation by the FDM was followed by subjecting the so-obtained composition to a 3 liter pin-stirrer (or C-unit) operating at 100 rpm. The resulting product coming out of the pin stirrer had the appearance of a spread.

Comparative Example A

A second spreadable edible émulsion was prepared having the same recipe as Example 1. The émulsion was made with the same process, only with a différence in rework température. The rework température was 60°C. At this température there was no crystallised fat présent in the rework stream.

Claims (14)

1. Process for preparing a fat-continuous émulsion, which émulsion comprises 1583% of an aqueous phase and 17-85% of a fat phase, said fat phase comprising 10-100 % hardstock fat (weight % on total fat phase), and 0-90% oil (weight % on total fat phase), which process comprises the steps of:

a. providing a water-continuous dispersion at a température of between 0°C and 15°C comprising part ofthe aqueous phase as the continuous phase with dispersed therein part ofthe oil;

b. providing part of hardstock fat in melted form and at a température of between 30°C and 60°C;

c. providing a fat-continuous dispersion which comprises the remainder of the aqueous phase, the remainder of the oil, and the remainder of the hardstock, which dispersion comprises fat crystals in an amount of from 0.2 to 10% by weight, based on the total dispersion provided by this step c.;

d. combining the water-continuous dispersion of step a. with the melted hardstock fat of step b. and the fat-continuous dispersion of step c, wherein the weight ratio of water-continuous dispersion + melted hardstock : fat-continuous dispersion is from 100 : 1 to 5 : 1;

e. subjecting the mixture obtained after step d. to a high shear device to provide a fat-continuous émulsion;

wherein the température of the mixture obtained from step d. is below the melting point of the hardstock fat.

2. Process according to claim 1, wherein the water-continuous dispersion of step

a. is obtained by mixing continuously in-line an aqueous phase at a température of from 0 to 15°C with oil at a température of from 0 to 25°C.

3. Process according to claim 1, wherein the dispersion of step a. is obtained by providing a stirred tank comprising oil dispersed in the aqueous phase, which stirred tank is held at a température of from 0 to 15°C for at least 30 minutes.

4. Process according to any of the preceding claims, wherein the dispersion in step c. comprises a rework stream ofthe product produced by step e.

5. Process according to any of the preceding claims, wherein the fat-continuous dispersion in step c. is at a température of between 20 and 50°C prior to combining with the dispersion of step a. and the hardstock of step b in step d.

6. Process according to any of the preceding claims, wherein the température of the water-continuous dispersion in step a. is between 0 and 10°C.

7. Process according to any of the preceding claims, wherein the température of the melted hardstock in step b. is between 30 and 45°C.

8. Process according to any of the preceding claims, wherein the watercontinuous dispersion of step a. is combined in step d. with the melted hardstock fat of step b. and the fat-continuous dispersion of step c, in a weight ratio of water-continuous dispersion + melted hardstock : fat-continuous dispersion is from 40 : 1 to 10 : 1.

9. Process according to any of the preceding claims, wherein step e. is carried out in a continuous process.

10. Process according to any ofthe preceding claims, wherein the high shear device is a high shear mixing process in a high shear mixer having a rotor and a stator, which mixer has a résidence time of less than 3 seconds, and sufficient shear to effect émulsification of water droplets in oil having a droplet size D₃₃ of less than 15 micrometer.

11. Process according to any of the preceding claims, wherein subjecting the mixture in step e. to a high shear device is followed by subjecting the mixture to a pin stirrer.

12. Process according to any ofthe preceding claims, wherein the fat continuous émulsion is a spreadable émulsion.

13. Process according to any of the preceding claims, wherein the émulsion comprises 40-80% fat.

14. Process according to any ofthe preceding claims, wherein the overall composition of the fat-continuous dispersion of step c. is the same as the overall composition of the fat-continuous émulsion produced by step e.