Process of compacting a microporous fat powder and compacted powder so obtained

Abstract

The invention relates to a compacted microporous fat powder that can suitably be used as an oil structuring agent. The compacted microporous fat powder has a freely settled density in the range of 90-600 g/l; a particle size distribution with at least 90 vol. % of the particles having a diameter in the range of 20 to 600 μm; a maximum G′.sub.i/G′.sub.d ratio of more than 2.0, wherein G′ represents the elastic modulus at 10° C. of a dispersion of 2 wt. % of the compacted fat powder in glycerol, and wherein the maximum ratio is determined by recording G′.sub.i whilst increasing the frequency from 0.1 to 15 s.sup.−1, by subsequently recording G′.sub.d whilst decreasing said frequency from 15 to 0.1 s.sup.−1 and by calculating the ratio G′.sub.i/G′.sub.d at the frequency at which said ratio is highest.

Claims

1. A compacted microporous fat powder, comprising: a fat content of at least 50 wt. %; a solid fat content at 20° C. (N.sub.20) of at least 10 wt. %; a free flowing density in the range of 90-600 g/l; a particle size distribution with at least 90 vol. % of the particles having a diameter in the range of 3 to 400 μm; a maximum G′.sub.i/G′.sub.d ratio of more than 2.0, wherein G′ represents the elastic modulus at 10° C. of a dispersion of 2 wt. % of the compacted fat powder in glycol, and wherein the maximum G′.sub.i/G′.sub.d ratio is determined by recording G′.sub.i while increasing the frequency from 0.1 to 15 s.sup.−1, by subsequently recording G′.sub.d while decreasing said frequency from 15 to 0.1 s.sup.−1, and by calculating the ratio G′.sub.i/G′.sub.d at the frequency at which said ratio is highest; wherein the compacted microporous fat powder has a full width at half maximum of the first order long spacing X-diffraction peak that is less than 0.00056× free flowing density +0.213.

2. The compacted microporous fat powder of claim 1, wherein the G′.sub.i/G′.sub.d ratio is at least 2.5.

3. The compacted microporous fat powder of claim 1, wherein the G′.sub.i/G′.sub.d ratio is at least 3.0.

4. The compacted microporous fat powder of claim 1, wherein the compacted microporous fat powder contains less than 30 wt. % of ingredients other than solid fat particles.

5. The compacted microporous fat powder of claim 1, wherein the compacted microporous fat powder contains less than 30 wt. % of free liquid oil.

6. A food product comprising the compacted microporous fat powder of claim 1 and an oil, wherein the compacted microporous fat powder is combined with the liquid oil in a weight ratio in the range of 1:100 to 40:100.

7. The food product of claim 6, wherein the food product comprises at least 18 wt. % of a continuous fat phase.

8. The food product of claim 6, wherein the food product comprises a spread, margarine, or shortening.

9. A method of producing a food product, comprising the step of: mixing the compacted microporous fat powder of claim 1 with a liquid oil to produce the food product, wherein the compacted microporous fat powder is combined with the liquid oil in a weight ratio within the range of 1:100 to 40:100.

10. The method of claim 9, further comprising the following step: packaging the food product, wherein the mixture comprising the compacted microporous fat powder and the oil is maintained at a temperature below the melting point of the fat powder until the food product is packaged.

11. The compacted microporous fat powder of claim 1, wherein the compacted microporous fat powder was produced by an extruder configured to have a barrel comprising a plurality of venting openings having a shorter dimension that exceeds the volume weighted average diameter of an input fat powder feed and that is less than 10 mm.

12. The compacted microporous fat powder of claim 1, wherein the G′.sub.i/G′.sub.d ratio is at least 4.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) Accordingly, one aspect of the invention relates to a process for compacting a microporous fat powder in an extruder, said microporous fat powder having the following characteristics: a fat content of at least 50 wt. %; a solid fat content at 20° C. (N.sub.20) of least 10 wt. %; a freely settled density in the range of 10 to 200 g/l, preferably in the range of 20 to 150 g/l; a particle size distribution with at least 90 wt. % of the particles having a diameter in the range of 3 to 400 μm, preferably in the range of 5 to 300 μm; said process comprising: feeding the fat powder into the feed zone of an extruder having a forwarding screw and a barrel within which said screw is centrally positioned; rotating said forwarding screw to advance said fat powder feed through a compacting zone of the extruder where the barrel comprises a plurality of venting openings having a shorter dimension that exceeds the volume weighted average diameter of the fat powder feed and that is less than 10 mm; and expelling the compacted fat powder from the extruder;

(2) wherein the temperature of the fat powder during passage through the extruder is maintained below 40° C. and wherein the compaction factor achieved exceeds 1.5.

(3) The term “fat” as used herein encompasses triglycerides, diglycerides, monoglycerides, free fatty acids, phospholipids and combinations thereof. Fat may be liquid or solid at ambient temperature.

(4) The term “microporous” as used herein in relation to powders refers to a particulate fatty material that is made up of particles that comprise a plurality of pores, holes, and/or channels.

(5) The solid fat content of a fat at a given temperature of x° C. (N.sub.x) can be determined by NMR pulse technique using the procedure described in Fette, Seifen, Anstrichmittel 80, (1978), 180-186.

(6) The “compaction factor” is defined herein as the ratio that is obtained when the freely settled density of the compacted powder obtained in the present process is divided by the freely settled density of the microporous fat powder that is used as the starting material in the same process. Thus, if the microporous fat powder that is used as a starting material has a freely settled density of 90 g/l and the compacted powder produced has a freely settled density of 240 g/l, the compaction factor equals 240/90=2.67.

(7) Whenever reference is made herein to the melting point of a fat or a fat powder, said melting point is determined by ISO method 6321:2002 (Animal and vegetable fats and oils—Determination of melting point in open capillary tubes (slip point)).

(8) The particle size distribution of compacted and non-compacted fat powders can suitably be determined with the help of a QICPIC™ image analysis sensor (ex Sympatec).

(9) Besides fat the microporous fat powder may suitably contain minor amounts of other ingredients, such as flavouring, anti-oxidants, emulsifiers, vitamins, minerals and colouring.

(10) Typically, the fat powder contains at least 80 wt. %, more preferably at least 90 wt. % and most preferably at least 95 wt. % of fat.

(11) Triglycerides and diglycerides together typically represent at least 80 wt. %, more preferably at least 90 wt. % and most preferably at least 95 wt. % of the fat. According to a particularly preferred embodiment, triglycerides constitute at least 80 wt. %, more preferably at least 85 wt. % and most preferably at least 90 wt. % of the fat.

(12) The benefits of the present invention are most pronounced in case a fat powder is employed that has a solid fat content at 20° C. (N.sub.20) of at least 20 wt. %, more preferably of at least 35 wt. % and most preferably of at least 50 wt. %.

(13) According to a particularly preferred embodiment the fat powder has a solid fat contents N.sub.10 from 50 to 100, N.sub.20 from 26 to 95 and N.sub.35 from 5 to 60.

(14) The fat powder employed in the present process typically has a melting point in excess of 35° C. More preferably, the fat powder has a melting point in excess of 40° C., even more preferably in excess of 44° C. and most preferably in excess of 48° C.

(15) Advantageously, the fat powder of the present invention is a free flowing powder. According to a particularly preferred embodiment, the freely settled density of the fat powder lies in the range of 30 to 120 g/l.

(16) The microporous fat powder that is fed into the feed zone of the extruder typically has a particle size distribution with at least 90 wt. % of the particles having a diameter in the range of 8 to 200 μm,

(17) In accordance with another preferred embodiment, the fat powder has a volume weighted average particle size in the range of 20 to 250 μm, more preferably in the range of 25 to 200 μm, and most preferably in the range of 30 to 150 μm.

(18) In order to ensure that the oil-structuring properties of the fat powder are retained after compaction, it is important that not more than a minor fraction of the solid fat contained in the powder becomes molten during extrusion. Thus, in accordance with a preferred embodiment, the amount of solid fat that is molten during extrusion does not exceed 30%, preferably does not exceed 15% by weight of the fat powder.

(19) Typically, during the compacting in the extruder the temperature of the microporous fat powder is maintained at a temperature that is at least 5° C., more preferably at least 10° C. and most preferably at least 15° C. below the melting point of the fat powder.

(20) During the compacting in the extruder the temperature of the fat powder is advantageously maintained in the range of −5-25° C., more preferably in the range of 0-20° C. and most preferably in the range of 3-15° C.

(21) The compaction factor achieved in the present process typically lies in the range of 1.5 to 10. Particularly good results are obtained with the present process if the compaction factor achieved lies in the range of 1.7 to 6, especially in the range of 1.9 to 3.0.

(22) The compaction factor achieved in the process is largely determined by the extent to which the volume accommodated in the screw flights decreases in the (axial) direction of extrusion. A “screw flight” is the volume defined by adjacent screw threads completing one complete turn on the screw shaft. Compaction can be achieved in the compacting zone of the extruder by gradually decreasing the screw flight in the direction of extrusion. This may be achieved, for instance, by decreasing the pitch of the forwarding screw and/or by reducing the height of the thread of the forwarding screw in the same direction and/or by increasing the shaft diameter, all in the direction of extrusion.

(23) In accordance with a preferred embodiment, within the compacting zone the screw flight decreases by at least a factor 1.5, more preferably by a factor 1.7 and most preferably by a factor 1.9 in the direction of extrusion. Typically, the screw flight decreases by not more than a factor 8 in the direction of extrusion. Even more preferably, the screw flight decreases by not more than a factor 6 in the direction of extrusion.

(24) As explained herein before, the present process offers the advantage that it can be operated efficiently at high throughput. Advantageously, the present process is used to process at least 100 kg/hr, more preferably at least 300 kg/hr and most preferably at least 800 kg/hr of microporous fat powder.

(25) In the present process effective compaction can be achieved when the forwarding screw is rotated at more than 5 rpm. Preferably, the forwarding screw is rotated at more than 15 rpm.

(26) Most preferably, the forwarding screw is rotated at more than 40 rpm. Typically, the forwarding screw is rotated at not more than 400 rpm.

(27) As explained herein before, the dimensions of the venting openings, especially the shorter dimension of these openings, are a critical feature of the present process. If the venting openings are too small clogging will occur. If the venting openings are too large compaction efficiency will be lost.

(28) The venting openings in the compacting zone of the extruder have a shorter dimension that exceeds the volume weighted average diameter of the fat powder feed. According to a particularly preferred embodiment, at least 60 wt. %, more preferably at least 70 wt. % and most preferably at least 75 wt. % of the particles contained in the fat powder feed have a diameter that is less than the shorter dimension of the venting openings.

(29) In accordance with a particularly preferred embodiment, the shorter dimension of the venting openings exceeds 50 μm. Even more preferably, the shorter dimension exceeds 100 μm. Typically, the shorter dimension does not exceed 10 mm. More preferably, said shorter dimension does not exceed 5 mm, most preferably it does not exceed 3 mm.

(30) The venting openings comprised in the barrel of the extruder typically have an aspect ratio 1:1 to 10,000:1. More preferably the aspect ratio is in the range of 1:1 to 5,000:1, even more preferably in the range of 1:1 to 1,000:1.

(31) In order to ensure that air can escape at an adequate rate, the barrel of the extruder used in the present process typically comprises at least 20 venting openings in the compacting zone. Even more preferably, the barrel contains at least 100 venting openings and most preferably it contains at least 200 venting openings.

(32) Together, the venting openings typically represent less than 60% of the surface area of the barrel in the compacting zone. More preferably, the venting openings represent less than 50%, most preferably less than 40% of the surface area of the barrel. The venting openings typically represent at least 3%, more preferably at least 5% and most preferably at least 10% of the surface area of the barrel in the compacting zone.

(33) As explained herein before, despite the fact that the venting openings in the barrel are larger than most of the particles contained in the fat powder, not more than a minor fraction of the fat powder goes through the venting opening in the present process. Typically, less than 30 wt. %, even more preferably less than 20 wt. % and most preferably less than 15 wt. % of the fat powder feed that is advanced through the compacting zone exits the barrel through the venting openings.

(34) As explained herein before, it was found that when the fat powder that exits the compacting zone through the venting opening is (re)combined it with the compacted fat powder that is expelled axially from the extruder, the overall compaction factor can still be sufficient. Thus, in accordance with a particularly preferred embodiment of the present process, the fat powder that leaves the compaction zone through the venting openings is combined with the compacted fat powder that is expelled from the extruder. Advantageously, said combining comprises mixing of the two fat powders.

(35) The compacted fat powder obtained in the present process typically has a freely settled density of at least 90 g/l, more preferably of 120 to 600 g/l, even more preferably of 130 to 400 g/l and most preferably of 150 to 300 g/l.

(36) In order to ensure that friction heat does not cause the fat powder to melt during extrusion, it is preferred that the barrel and/or the forwarding screw are actively cooled during the process.

(37) Unlike the extrusion process described in GB 2 208 378 no suction needs to be applied to remove gas through the venting openings. Thus, advantageously the extruder employed in the present process does not comprise an evacuation chamber as described herein before in relation to GB-A 2 208 378.

(38) Another aspect of the present invention relates to a compacted microporous fat powder having the following characteristics: a fat content of at least 50 wt. %; a solid fat content at 20° C. (N.sub.20) of least 10 wt. %; a freely settled density in the range of 90-600 g/l; a particle size distribution with at least 90 vol. % of the particles having a diameter in the range of 20 to 600 μm; a maximum G′.sub.i/G′.sub.d ratio of more than 2.0, wherein G′ represents the elastic modulus at 10° C. of a dispersion of 2 wt. % of the compacted fat powder in glycerol, and wherein the maximum G′.sub.i/G′.sub.d ratio is determined by recording G′.sub.i whilst increasing the frequency from 0.1 to 15 s.sup.−1, by subsequently recording G′.sub.d whilst decreasing said frequency from 15 to 0.1 s.sup.−1, and by calculating the ratio G′.sub.i/G′.sub.d at the frequency at which said ratio is highest.

(39) The inventors have found that the compacted microporous fat powder of the present invention comprises agglomerates that are composed of fat particles that are loosely bound together. If these agglomerates are subjected to conditions of mild shear, the agglomerates break up (de-agglomeration). It is believed that the oil structuring capacity of the compacted microporous fat powder is largely determined by the non-agglomerated fat particles and that the compacted fat powder has retained this capacity because the fat particles are quickly released form the agglomerates when the compacted fat powder is dispersed in a liquid and the resulting slurry is subjected to shear (e.g. stirring).

(40) The presence of agglomerates of fat particles that easily break up under conditions of mild shear is reflected by the requirement that the G′.sub.i/G′.sub.d ratio exceeds 2.0.

(41) The elastic modulus G′ is the mathematical description of an object or substance's tendency to be deformed elastically (i.e., non-permanently) when a force is applied to it. The elastic modulus of an object is defined as the slope of its stress-strain curve in the elastic deformation region: λ=stress/strain wherein lambda (λ) is the elastic modulus; stress is the restoring force caused due to the deformation divided by the area to which the force is applied; and strain is the ratio of the change caused by the stress to the original state of the object.

(42) G′ of the present compacted powder is determined by placing a sample of the powder-in-glycerol dispersion between two oscillating plates that have been equilibrated at 10° C. G′ is determined as a function of frequency, using an upward sweep of 0.1 to 15 Hz to monitor G′.sub.i, followed by a downward sweep from 15 to 0.1 Hz to monitor G′.sub.d. The oscillating plates exert a certain amount of shear that increases with frequency. The agglomerated fat particles contained in the compacted powder of the present invention are gradually broken up as the oscillation frequency increases. As a result, the G′ values measured at lower frequencies during the downward sweep are substantially lower than those that were measured at these same frequencies during the upward sweep. In contrast, for non-compacted powders the G′ curves of the upward and downward sweep are essentially identical.

(43) According to a particularly preferred embodiment, the G′.sub.i/G′.sub.d ratio is at least 2.5, more preferably at least 3.0 and most preferably at least 4.0. Preferably, the compacted powder exhibits the latter ratio's at a frequency of 1 Hz, using the oscillation procedure described herein before.

(44) The preferred fat contents and solid fat contents for the compacted microporous fat powder are identical to those already mentioned herein before in relation to the (non-compacted) fat powder.

(45) Unlike the granulates described in WO 2006/087092 the compacted fat powder of the present invention is not made of agglomerates of fat particles that are held together by a sticky liquid, such as edible oil or a water-in-oil emulsion. The present compacted fat powder typically contains less than 30 wt. %, more preferably less than 20 wt. %, even more preferably less than 10 wt. % and most preferably less than 5 wt. % of free liquid oil.

(46) In accordance with another preferred embodiment, the compacted fat powder contains less than 30 wt. %, more preferably less than 20 wt. %, even more preferably less than 10 wt. % and most preferably less than 5 wt. % of ingredients other than solid fat particles.

(47) WO 2010/069746 and WO 2010/069750 describe microporous fat powders that may be used as oil-structuring agents. Unlike the fat powders described in these international patent applications, the compacted fat powder of the present invention typically has a full width at half maximum of the first order long spacing X-diffraction peak that is less than 0.00056×free flowing density+0.213.

(48) The compacted microporous fat powder of the present invention is preferably obtainable, or even more preferably obtained by a compacting process as defined herein before.

(49) Another aspect of the invention relates to the use of the compacted microporous fat powder as defined herein before as an oil-structuring agent, especially an oil-structuring agent for food products that contain at least 5 wt. % of liquid oil. Most preferably, the compacted fat powder is used as an oil-structuring agent in fat-continuous food products.

(50) Yet another aspect of the present invention relates to a process of preparing a food product, said process comprising mixing the compacted microporous fat powder as defined herein before with liquid oil.

(51) Typically, the compacted microporous fat powder is combined with the liquid oil in a weight ratio that lies in the range of 1:100 to 40:100, more preferably within the range of 3:100 to 25:100 and most preferably in the range 6:100 to 18:100.

(52) The present process preferably comprises packaging of the final food product. According to a particularly preferred embodiment, the temperature of the mixture of compacted microporous fat powder and liquid oil is kept below the melting point of the fat powder until the product is packaged.

(53) The food product obtained in the present process typically comprises at least 18 wt. % of a continuous fat phase.

(54) Examples of food product that may suitably be produced by the present process include spreads, kitchen margarines, bakery margarines and shortenings.

(55) The invention is further illustrated by means of the following non-limiting examples.

EXAMPLES

(56) Determination of the G′.sub.i/G′.sub.d Ratio

(57) A dispersion of fat powder in glycerol is prepared by adding 1 gram of fat powder to 49 grams of glycerol and by gently mixing the two components with a spatula (all ingredients being previously equilibrated at 5° C.). Next, about 3 grams of the slurry so obtained is placed on the bottom plate of a Peltier-controlled Rheometer (AR 2000, TA Instruments) which is thermostated at 10° C. The upper plate used in the Rheometer has a sand-blasted surface and a diameter of 40 mm.

(58) The gap size between the two oscillating plates is to be chosen carefully when determining the maximum G′.sub.i/G′.sub.d ratio. The G′ measurements described herein before should be performed with gap sizes of 200, 300 and 500 μm, and the gap size yielding the highest G′.sub.i/G′.sub.d ratio should be used for the final result.

(59) The maximum G′.sub.i/G′.sub.d ratio is determined within the frequency range of 0.3 to 10 Hz.

Comparative Example A

(60) A microporous fat powder was produced from an interesterified fat using the Super Critical Melt Micronisation methodology described in WO 2005/014158. The interesterified fat was a randomly interesterified blend of multifractionated palm oil stearin having an IV of 14 (65 wt. %) and palm kernel oil (35 wt. %). The microporous fat powder so obtained had the properties described in Table 1.

(61) TABLE-US-00001 TABLE 1 Freely settled density 60-80 g/l Volume weighted average diameter appr. 70 μm Melting point 48° C. N.sub.20 82.5%

(62) Compaction experiments were carried out in a cooled room at 5° C. The equipment was left long enough in this room to cool down to 5° C. The in-feed powder was stored at 5° C. and had a temperature of ca. 5° C.

(63) Extrusion compaction was carried out in an AZODOS extruder comprising an extrusion screw with an external diameter of 55 mm (AZO Inc.). This particular extruder is a dosing system with a constant pitch and a pneumatically operated flat-shaped shut-off valve that can be used to give counter pressure for compaction.

(64) A first trial resulted in compaction factors ranging from 3.2-4.8 at a throughput up to ca. 6.1 kg/hr. The counter pressure needed to be low, ca. 0.5 bar, in order to prevent shut-off. The in-feed section needed manual mixing in order to prevent bridging and pit-holes.

Comparative Example B

(65) Comparative Example A was repeated except that this time a screw with varying pitch was used. The pitch at the in-feed section of the screw was increased from ca. 30 mm to 60 mm. At the compaction side the pitch decreased from 60 mm to appr. 20 mm.

(66) This resulted in a relatively constant compaction factor of 2.2-2.3 at throughputs from 4.6 to 8.1 kg/hr. The throughput increases with the rotational speed of the screw. At screw speeds higher than ca. 50 rpm, sufficient compaction was lost and/or the throughput did not increase significantly anymore.

Example 1

(67) Comparative Example B was repeated with the exception that the barrel of the extruder was replaced with a barrel containing a perforated stainless steel tube section having the properties described in Table 2.

(68) TABLE-US-00002 TABLE 2 Shape of the perforations Circular Shortest dimension of perforations  1.5 mm Wall thickness of the perforated section  1.5 mm Percentage surface perforated 31% Length of perforated section  285 mm

(69) The manual mixing in the in-feed section was replaced by an automated in-feed mixer. The pitch at the in-feed section of the screw was increased from ca. 30 mm to 60 mm. At the compaction side the pitch decreased from ca. 60 mm to ca. 12 mm.

(70) A constant compaction factor of 2.4-2.5 could be achieved at throughputs of up to 21.2 kg/hr (112 rpm). Temperature of the fat powder was found to increase around 3-4° C. in the compaction zone of the extruder.

(71) The amount of fat powder that exited the extruder through the perforations in the extruder barrel was less than 15% by weight of the feed. This powder was mixed with the compacted fat powder that was expelled axially by the extruder. The compaction factors mentioned are measured from the combined out-feed.

Example 2

(72) Example 1 was repeated, except that this time the feed consisted of a freshly produced fat powder instead of a fat powder that had been stored at 5° C.

(73) Compaction extrusion was started within 3 minutes after the powder had been produced. The powder at the in-feed section for compaction had a temperature of approximately 7° C.

(74) The compaction factor and throughputs realized were very similar to those described in Example 1.

Example 3

(75) Example 2 was repeated, except that the extruder was replaced with a similar extruder that can be operated at higher throughputs as the external screw diameter was 90 mm (instead of 55 mm). The pitch of the screw of this extruder decreased from 100 mm to ca. 25 mm in the compaction zone. The length of the perforated section was 300 mm.

(76) Compaction extrusion was started approximately 15 minutes after the last powder had been produced. The powder at the in-feed section for compaction had a temperature of approximately 10° C.

(77) A constant compaction factor of about 2.2 could be realized at throughputs of up to 190 kg/hr (157 rpm). Temperature of the fat powder was found to increase around 4° C. in the compaction zone of the extruder.

Example 4

(78) The compacted powders described in Example 1 and 3, were used to produce a spread, using the recipe (Composition B) and process described in the Examples of WO 2010/069746. A reference spread was produced using the non-compacted powder instead of the compacted powder.

(79) It was found that compaction had a negligible effect on the spread quality. The water droplets in the spread produced with the compacted powder were in some cases slightly larger than those in the reference spread. However, this difference could be negated very easily by increasing the speed of the C-unit (pin stirrer).

Example 5

(80) The compacted powder described in Example 3 and the fat powder that was used as a starting material for the production of that compacted powder were both subjected to a rheological test as described herein before (using a gap space of 300 μm) to determine the maximum G′.sub.i/G′.sub.d ratio.

(81) The results so obtained are summarized in Table 3.

(82) TABLE-US-00003 TABLE 3 G′ Non- G′.sub.i/G′.sub.d ratio Frequency Compacted compacted Non- (in Hz) Up Down Up Down Compacted compacted 0.29 67.9 10.4 24.0 24.4 6.5 1.0 0.48 78.0 9.8 20.9 15.1 7.9 1.4 0.85 82.4 10.9 18.2 16.1 7.6 1.1 1.23 87.1 12.4 17.0 17.2 7.0 1.0 1.99 82.8 14.6 16.7 19.6 5.7 0.9 3.12 75.2 17.7 18.3 22.1 4.3 0.8 5.00 51.9 21.1 21.7 25.9 2.5 0.8 8.02 39.2 26.7 27.1 30.9 1.5 0.9 12.9 44.4 36.7 35.0 35.7 1.2 1.0

(83) This data shows that the maximum G′.sub.i/G′.sub.d ratio for the compacted powder was 7.9, whereas the maximum G′.sub.i/G′.sub.d ratio for the non-compacted powder was only 1.4.