Process for preparing a fat slurry and for preparing a spread with said slurry

Abstract

A process for preparing a slurry of edible oil and fat powder, and to a process of preparing an edible fat-continuous spread out of such. The process for preparing said slurry has at least two different regimes of reduced pressure.

Claims

1. Process for preparing an edible fat slurry comprising 70-98% by weight (of the total slurry of oil and fat powder) of an edible oil and 2-30% by weight (of the total slurry of oil and fat powder) of fat powder, wherein the fat powder is a micronised fat powder of a structuring fat, said process comprising the steps of: a) providing the fat powder; b) providing the oil; c) combining the fat powder and the oil in a mixing vessel; d) mixing the oil and fat powder in the mixing vessel to a fat slurry for a period of 1 to 8 minutes at a pressure of below 0.25 bar; e) subjecting the mixing vessel to a pressurising step of 30 seconds to 6 minutes to raise the pressure in the mixing vessel to at least 0.3 bar, during which the shear in the mixing vessel is less than the shear in step g); f) subjecting the mixing vessel to a de-pressurising step of 1 to 10 minutes to reduce the pressure in the mixing vessel to below 0.25 bar; and g) subjecting the content of the mixing vessel to a stirring operation for 3 to 10 minutes; wherein the temperature of the fat powder, oil phase, and mixture thereof is kept at a temperature of below 35 C.

2. The process of claim 1, wherein the successive steps e) to g) are repeated at least once.

3. The process of claim 2, wherein the successive steps e) to g) are repeated until the viscosity of the content in the mixing vessel has reached a viscosity of at least 8 dPa.Math.s.

4. The process of claim 1, wherein the pressure in steps d) and f) is reduced to below 0.2 bar.

5. The process of claim 1, wherein the de-pressurising step f) and the mixing step g) are effected in a total time of 2 to 10 minutes.

6. The process of claim 1, wherein after step g) the pressure is brought up to atmospheric pressure.

7. The process of claim 1, wherein the oil and the fat powder are mixed by one or more of (a) recirculation means, (b) a dynamic mixer, and (c) a stirrer in the mixing vessel.

8. The process of claim 7, wherein recirculation means comprises an in-line mixer.

9. The process of claim 8, wherein the stirring operation in step g) is carried out for at least the time equal to the average residence time in the vessel with recirculation means.

10. The process of claim 1, wherein the amount fat powder on the total fat slurry is from 2 to 20% by weight, based on the total fat slurry.

11. The process of claim 1, wherein the pressure at step e) is raised in the mixing vessel to from 0.3 to 0.7 bar.

12. The process of claim 5, wherein the de-pressurising step f) and the mixing step g) are effected in a total time of 3 to 8 minutes.

13. The process of claim 1, wherein the pressure in steps d) and f) is reduced to below 0.1 bar.

14. The process of claim 2, wherein the successive steps e) to g) are repeated until the viscosity of the content in the mixing vessel has reached a viscosity of at least 10 dPa.Math.s.

15. A process for making an edible oil-continuous emulsion containing 15-80% (by weight of the total emulsion) of a fat phase and 20-85% (by weight of the total emulsion) of an aqueous phase, which process comprises the steps of a) providing the aqueous phase at a temperature below 35 C., b) providing a fat slurry of oil and fat powder, c) mixing said aqueous phase and said fat slurry to obtain an oil-continuous emulsion, wherein said fat slurry is obtained by the process comprising the steps of claim 1.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1: Graphical representation of the development of slurry (vegetable oil with fat powder) viscosity in time during mixing in Trial 1, 4 or 5.

DETAILED DESCRIPTION OF THE INVENTION

(2) When powders such as fat powders, especially fat powders with a very low bulk density (examples are micronized fat powders) are to be mixed with oil, e.g. at concentrations of 1-10 weight % powders on 90% oil, this is preferably achieved at a reduced pressure. A reduced pressure makes that wetting is quicker and also any potential remainder of the gas used in production of the fat particles (entrapped in the small cavities) that could prevent complete mixing with oil is thus removed.

(3) Still, there was room for improvement. Depending e.g. on the type of oil, the type of the fat powder, the amount, the type of mixer, even shorter times of mixing may be desired. In the process according to the invention it was shown that by introducing a stage in which there is less deep vacuum (i.e. or no vacuum) and less shear, better results can be obtained. The improvement is seen in faster build up of the desired viscosity.

(4) It will be clear that when going from e.g. a pressure of about 0.25 bar to a pressure of about 0.6 bar, this costs time. In the claimed process, the indicated times are the time intervals at which the pressure is within the claimed range. Still, mixing may continue or may be discontinued in the process of going from e.g. 0.2 bar to 0.6 bar. What matters is that for a time interval as mentioned, the pressure is within the claimed level. The pressure can be increased, such as by opening a valve to let air or nitrogen in, or decreased, such as by use of a vacuum pump.

(5) In the process according to the invention, it may be preferred that steps f) and g) are carried out at least partially simultaneously. In other words, during the reduction of the pressure there may be stirring, stirring may also start later when the desired low pressure is achieved.

(6) The cycle of less deep vacuum with low shear (step e in the process as set out above) followed by deeper vacuum pressure/high shear (steps f and g) may be repeated for 1-10 times, preferably 2 to 6 times. Hence, it is preferred that in the process according to the invention, the successive steps e) to g) are repeated at least once. Preferably, they are repeated 2 to 6 times. As the cycling of deep vacuum and high shear followed by less deep vacuum and less shear, optionally to be repeated for 1-10 times, preferably 2 to 6 times are to act on the micronized fat powder, and as it is desired to reach the desired high end viscosity as quickly as possible, it is preferred that all of the micronized fat powder is included in the mixing vessel in step c.

(7) For a process in which microporous fat particles are mixed with oil, at which microporous particles are broken down into smaller particles, the viscosity of the oil/particle slurry will increase. For these fat slurries, the viscosity increase is desired, and a minimum viscosity can be the target. Higher viscosity relates to more intense mixing, and following this, in the present invention, it is preferred that the successive steps e) to g) are repeated until the viscosity of the content in the mixing vessel has reached a viscosity of at least 5 dPa.Math.s, preferably at least 8 dPa.Math.s, more preferably at least 10 dPa.Math.s.

(8) In the present process, some steps are carried out at a low pressure, below 0.25 bar. However, it may be preferred that the pressure in steps d) and f) is reduced to below 0.2 bar, preferably to below 0.15 bar, more preferably to below 0.1 bar.

(9) Depending on e.g. the amount of fat powder and the mixing equipment the various steps may be carried out longer or shorter. In the present invention, it is preferred that the de-pressurising step f) and the mixing step g) are effected in a total time of 2 to 10 minutes, preferably in a total time of 3 to 8 minutes.

(10) When it is concluded mixing is finished, e.g. as can be determined when a certain viscosity is reached, the resulting oil slurry may be removed from the mixing vessel. Prior to doing so, it may be practical to raise the pressure to atmospheric, e.g. by opening a valve connected to the environment. Hence, it may be preferred that after step g) the pressure is brought up to atmospheric pressure.

(11) As mentioned, mixing is to be carried out of the fat powder and the oil. This may be carried out by any suitable means. Preferably, the oil and the fat powder are mixed by one or more of (a) recirculation means, (b) a dynamic mixer, and (c) a stirrer in the mixing vessel. When the mixing vessel contains a recirculation means as part of the mixing equipment, such will usually contain a pump, but it may also be preferred that the recirculation means (recirculation loop or tube) comprises mixing means, preferably an in-line mixer, preferably a dynamic in-line mixer. In case of a recirculation means being present, the stirring time in the mixing vessel can suitably be adapted to the average residence time of the content in the mixing vessel, e.g. so that on average at least the whole content has (on average) gone through the recycle loop at least once. Hence, it may be preferred that the stirring operation in step g) is carried out for at least the time equal to the average residence time of the vessel with recirculation means.

(12) It will be clear that the fat powder is mixed with the oil to achieve that a slurry is obtained. This slurry can only exist if the temperature of the mixture oil+fat powder is kept below the melting point of the fat powder. In most cases fat powders will be used that melt at in the mouth conditions. Therefore the temperature of the fat powder, oil phase, and mixture thereof is kept at a temperature of below 35 C.

(13) The process of making the slurry of oil and fat powder may be carried out with any desired amount of fat powder, although it will be clear there is an upper limit above which viscosities will get too high for easy processing, and a lower limit below which there is little effect of the fat powder in the oil. Hence, it is preferred in the present invention that the amount fat powder on the total fat slurry is from 2 to 20% (preferably from 3 to 12%) by weight, based on the total fat slurry.

(14) The fat powder can be made by any suitable process for making fat powder. Suitable methods to prepare the fat powder include for example cryo-crystallization, in which atomized liquid droplets come in contact with liquid nitrogen causing the droplets to instantaneously solidify, and Super Critical Melt Micronisation (ScMM), also known as particles from gas saturated solutions (PGSS). ScMM is a commonly known method and is for example described in J. of Supercritical Fluids 43 (2007) 181-190 and EP1651338.

(15) The fat powder comprises hardstock fat and preferably comprises at least 80 wt. % of hardstock fat, more preferably at least 85 wt. %, even more preferably at least 90 wt. %, even more preferably at least 95 wt. % and even more preferably at least 98 wt. %. Still even more preferably the edible fat powder essentially consists of hardstock fat. The hardstock fat as present in the edible fat powder has a solid fat content N10 from 50 to 100, N20 from 26 to 95 and N35 from 2 to 60.

(16) The process is preferably carried out as a batch process.

EXAMPLES

(17) Water Droplet Size Distribution of W/O Emulsions

(18) The normal terminology for Nuclear Magnetic Resonance (NMR) is used throughout this method. On the basis of this method the parameters D3,3 and exp() of a lognormal water droplet size distribution can be determined. The D3,3 is the volume weighted mean droplet diameter and (e-sigma) is the standard deviation of the logarithm of the droplet diameter.

(19) The NMR signal (echo height) of the protons of the water in a water-in-oil emulsion are measured using a sequence of 4 radio frequency pulses in the presence (echo height E) and absence (echo height E*) of two magnetic field gradient pulses as a function of the gradient power. The oil protons are suppressed in the first part of the sequence by a relaxation filter. The ratio (R=E/E*) reflects the extent of restriction of the translational mobility of the water molecules in the water droplets and thereby is a measure of the water droplet size. By a mathematical procedurewhich uses the lognormal droplet size distributionthe parameters of the water droplet size distribution D3,3 (volume weighed geometric mean diameter) and (distribution width) are calculated.

(20) 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).

(21) Stevens Value

(22) Stevens values indicates a products hardness or firmness. The Stevens value was measured with a Stevens penetrometer (Brookfield LFRA Texture Analyser (LFRA 1500), ex Brookfield Engineering Labs, UK) equipped with a stainless steel probe with a diameter of 6.35 mm and operated in normal mode. The probe is pushed into the product at a speed of 2 mm/s, a trigger force of 5 gram from a distance of 10 mm. The force required is read from the digital display and is expressed in grams.

(23) Viscosity Measurement

(24) The viscosity was determined with a Haake viscotester 2 plus with R1 spindle (Rotor No. 1). The flow resistance of the dispersion (i.e. of the fat powder and oil slurry) is displayed while the spindle rotates at 62.5 rpm. The spindle was inserted in the dispersion so that the fluid level reached the immersion groove on the shaft of the spindle. Next, the spindle was attached to the viscometer. The viscosity was measured of the dispersion phase having a temperature of 20-24 degrees Celsius by setting the Haake viscosimeter 2 to program R1. The viscosity was measured in dPa.Math.s.

Example 1

(25) The composition of the fat phase used in Example 1: Trials 1, 4 and 5:

(26) TABLE-US-00001 % on % on spread product Fat phase fat phase (45% fat emulsion) .sup.1Micronized fat powder 10 4.5 vegetable oil blend 89.56 40.3 .sup.2lecithin 0.44 0.2 .sup.1The micronized fat powder was obtained using a supercritical melt micronisation process similar to the process described in Particle formation of ductile materials using the PGSS technology with supercritical carbon dioxide, P. Mnkl, Ph. D. Thesis, Delft University of Technology, 16 Dec. 2005, Chapter 4, pp. 41-51. The fat powder consisted of an interesterified mixture of 65% dry fractionated palm oil stearin with an Iodine Value of 14 and 35% palm kernel oil. .sup.2Soybean lecithin

(27) In the trails, either one (Trial 1) or two (Trial 4 and 5) shear regimes were used: high: (960 rpm of the high shear mixer, 3000 rpm for the in-line dynamic mixer and 12 rpm for the agitator) used in-line in trial 1 and in the 5 minute-periods in trials 4, 5; and low (or reduced): (480 rpm of the high shear mixer, 0 rpm for the in-line dynamic mixer and 12 rpm for the agitator) at the 2-minute-periods in trials 4 and 5.

(28) The temperature during the trials as described below were kept below the melting point of the hardstock comprised by the micronized fat powder.

(29) Trial 1:

(30) After combining the oil, lecithin and the powder in a stainless steel tank, the vacuum was maintained at 0.1 bar, and the mixture continuously mixed. Mixing took place by use of a stainless steel vessel (DU BG-type Zoatec), suitable to subject to vacuum and fitted with an agitator (12 rpm) and a high shear mixer (operated at 960 rpm) in the vessel. The vessel was further equipped with a re-circulation loop fitted with a circulation pump and an in-line dynamic mixer (operated at 3000 rpm).

(31) Trial 4: contained the following sequence: After combining the oil, lecithin and the powder, the mixture was 5 minutes stirred at 0.1 bar (first 5 minute period). Mixing also took place by use of a stainless steel vessel as described for Trail 1. The mixing speed in this first period was: agitator (12 rpm), high shear mixer (960 rpm), circulation pump on and in-line dynamic mixer (3000 rpm). then a valve on the vessel was opened for a short while to raise the pressure to 0.5-0.7 bar. The valve was closed, and stirring was continued at this pressure for in total 2 minutes after opening the valve. During this 2 minute-period, stirring was reduced of the in-line dynamic mixer (first 2 minute period) After this 2-minute period the pressure was lowered again by pumping out gas until a pressure of 0.1 bar was achieved. Stirring was continued for in total 5 minutes after starting to lower the pressure, and stirring was back at the level of the first 5 minutes. (second 5 minute period) Thereafter there was the same 2 minute period in which lower shear and a higher pressure were present like the first 2-minute period (second 2 minute period) Thereafter there was the same 5 minute period in which higher shear and a lower pressure were present like the second 5-minute period (third 5 minute period) Thereafter there was the same 2 minute period in which lower shear and a higher pressure were present like the first 2-minute period (third 2 minute period) Thereafter there was the same 5 minute period in which higher shear and a lower pressure were present like the second 5-minute period (fourth 5 minute period)

(32) Trial 5:

(33) Is a repetition of trial 4 regarding different mixer speeds (i.e. different shear regimes), but the pressure was maintained as in Trail 1 at 0.1 bar throughout the mixing.

(34) Hence, Trial 4 had the vacuum break method according to the invention, Trial 1 is a control by not manipulating the pressure (or shear), and Trial 5 is a control by only manipulating the shear, not the pressure.

(35) Of each trial, the viscosity of the slurry in the mixing vessel was measured. Results are set out in table 1 below.

(36) TABLE-US-00002 TABLE 1 dispersion development as measured by viscosity (minutes from start of the trial) Trail 1 Trail 4 Trail 5 Time from Viscosity Time from Viscosity Time from Viscosity start(mins) (dPa .Math. s) start(mins) (dPa .Math. s) start(mins) (dPa .Math. s) 5 3 5 4 10 2 12 4 12 5 20 4 19 6 19 6 26 12 26 7 30 8 33 14 33 8 40 15

CONCLUSION

(37) In table with the results and FIG. 1 it can clearly be seen that the 5-2 Sequence method (i.e. according to Trial 4 and according to the invention) had a positive influence on the viscosity development of the dispersion. By comparing with the trials in which the vacuum was not released, the effect of the vacuum release is clear. When the vacuum is not released the viscosity development is much less than with vacuum release. Also many white particles remain visible. With the 5-2 Sequence method at 33 minutes much less white particles were visible in the dispersion. With light microscopy and polarized light a very smooth dispersion with small crystals could be observed.

Example 2

(38) In a serie's of dispersion experiments 4 different preparation times and 2 different vacuum release systems were tested. Again the viscosity was measured. The shear settings and pressures were about the same as in example 1. The results are set out in table 2 below. The viscosity numbers are based on averages from 3 to 5 experiments (except for trial B, which is based on a single experiment).

(39) TABLE-US-00003 TABLE 2 Dispersion development data with different mixing times and vacuum break sequence. Viscosity in the Total vacuum vessel after dispersion Dispersion dispersion mix time Trial mix time method (dPa .Math. s) A 26 5-2 10.4 B 40 5-2 21 C 26 2-4 12.3 D 12 5-2 11.5 E 19 5-2 8

Example 3

(40) 45% fat spreads were successfully made using the dispersions from table 2, according to Trails A, B and C.

(41) The spreads (i.e. oil-continuous emulsions) were made by the following process: The water phase is prepared in a run tank by adding hot water in to the tank and adding the proper amount of salt, and adjusting the pH to about 3.9 with lactic acid. The water phase was cooled before entering the C-unit via a tubular heat exchanger (THE) to about 6-8 C. In a 50 liter C-unit (operating at 500-900 rpm) the water phase and the fat dispersion of example 2 were mixed and turned into a spread.

(42) The composition of the water phase was:

(43) TABLE-US-00004 % on % on product Water phase phase (45% fat) Water 97.0 53.35 Salt 3.0 1.65 Lactic acid 0.009 0.00495

(44) Results:

(45) Typical D3.3 and Stevens values of the 45% fat products obtained were:

(46) TABLE-US-00005 D3.3 Stevens value (m) e{circumflex over ()}sigma (gram) 5-7 1.5-2.0 5-7

Example 4

(47) Four 30% fat spreads were made with the dispersions according to Trials D from table 2. The composition of the fat phase was as below

(48) TABLE-US-00006 % on % on spread product Fat phase fat phase (30% fat) .sup.1Micronized fat powder 12 3.6 vegetable oil 86.83 26.05 .sup.2lecithin 0.5 0.15 Unsaturated Monoglyceride 0.5 0.15 Saturated Monoglyceride 0.17 0.05 .sup.1The fat powder used is as was described for Example 1. .sup.2Soybean lecithin,

(49) The mixing of the fat powder and oil blend was conducted as described in example 1 trial 4, only for a total mixing time of 12 minutes.

(50) Results:

(51) Typically the D3.3 and Stevens values at processing of this 30% fat product were:

(52) TABLE-US-00007 D3.3 Stevens value (m) e{circumflex over ()}sigma (gram) 5-7 1.5-1.8 8-10

(53) Overall Conclusions Vacuum break is a tool to speed up the development of the dispersion and therefore reduce the mixing time.