Process for the preparation of an edible fat-containing product

Process for the preparation of an edible fat-containing product wherein a fat-containing fraction (a) of the composition which is to constitute the product is cooled to cause crystallization of part of the fat and a fraction (b) of the composition is mixed with fraction (a) containing partially crystallized fat in a mixer comprising two closely spaced mutually displaceable surfaces, each having a pattern of cavities which overlap during movement of one surface with respect to the other, between which surfaces the fractions to be mixed pass, and according to a preferred embodiment 10 to 99.99% of fraction (a) is mixed with 90 to 0.01% of fraction (b), calculated as volume % on the total composition.

FIELD OF THE INVENTION 
The present application is concerned with a process for the preparation of 
an edible fat-containing product. 
PRIOR ART 
In the preparation of edible fat-containing products, such as e.g. 
margarine, shortening and low calorie spreads, it is common practice to 
mix all ingredients and then subject the mixture to cooling and working 
operations in a series of one or more scraped-surface heat exchangers and 
agitated crystallizers, e.g. as described in A. J. C. Anderson, Margarine, 
Pergamon Press Limited, London, 1954, pages 228-229. 
Other processes have, however, also been described. 
A. J. C. Anderson, cited above, has described on pages 230-231 a process 
for preparing margarine wherein the fat blend and 25% of the milk are 
passed through two scraped-surface heat exchangers and the remainder of 
the milk is chilled and then injected under pressure into the semi-liquid 
material leaving the scraped-surface heat exchangers. The mixture is then 
passed through a blender, provided with rod-shaped beaters, which rotate 
at 700 r.p.m. and disperse the milk in the margarine. 
In JP No. 59 130 135 a process is described for the preparation of an 
edible fat product containing both butterfat and other fat by first 
separately preparing butter and margarine, heating the butter to 
10.degree.-23.degree. C. and mixing the butter with the margarine in a 
static mixer. 
From European patent application No. 101,104, it is known to prepare an 
edible oil and water-containing emulsion comprising inter alia processing 
an oil-in-water emulsion and a separate water phase followed by mixing 
these phases to obtain the final emulsion. 
British Pat. No. 1,327,511 describes mixing and emulsifying two separate 
process streams, one warm liquid containing crystallizable fat and a 
second, cold liquid containing substantially no crystallizable fat, 
followed by working and packing of the partially crystallized mixture. 
GENERAL DESCRIPTION 
The present invention provides a process for the preparation of an edible 
fat-containing product wherein a fat-containing fraction (a) of the 
composition which is to constitute the product is cooled to cause 
crystallization of part of the fat and a fraction (b) of the composition 
is mixed with fraction (a) containing partially crystallized fat in a 
mixer comprising two closely spaced, mutually displaceable surfaces, each 
having a pattern of cavities which overlap during movement of one surface 
with respect to the other, between which surfaces the fractions to be 
mixed pass. 
An essential aspect of the present invention is that it provides a process 
in which a part of the composition can be plastified and subsequently 
mixed with the remainder of the composition such that a sufficient degree 
of mixing can be achieved without subjecting the mixture to such severe 
working conditions that the structure imparted to the plastified part of 
the composition is destroyed to a large extent during the mixing. Because 
of this, improved products can be obtained by the present process. 
Another advantage of the process is that a sufficient degree of mixing, 
while maintaining the microstructure of the plastified fraction, can be 
obtained at relatively low pressure in the production line. 
The mixer used in the present process comprises two closely spaced, 
mutually displaceable surfaces, each having a pattern of cavities which 
overlap during movement of one surface with respect to the other. The 
material moving between the surfaces traces a path through cavities 
alternately in each surface. 
Preferably, the surfaces of the mixer have patterns of cavities such that a 
cavity on one of the surfaces continuously overlaps with at least two 
cavities on the other surface. In the preferred mixer for this process, 
the cavities are arranged to give constantly available but changing 
pathways through the device during movement of one surface with respect to 
the other. 
Suitably, the mixer has a cylindrical geometry. 
Preferably, the mixer comprises a stator and a rotor; the opposing faces of 
the stator and rotor carry the cavities through which the material passes 
during its passage through the device. The external cylinder may be 
rotatable while the internal cylinder is fixed, but preferably the 
external cylinder is the stator within which the rotor is journalled. 
The mixer may also have a planar geometry in which opposed plane surfaces 
having patterns of cavities would be moved mutually. Another geometry that 
can be used is a cone geometry. A mixer of such geometry can comprise a 
rotor and a stator having shapes of truncated cones. An advantage of a 
planar or cone geometry is that the distance between the two surfaces can 
be varied easily. Other geometries can also be suitable, but mixers having 
a cylindrical geometry are preferred. The rotor may be located 
eccentrically, but preferably it is placed centrically. 
Various configurations can be used for the shape of the cavities. The 
cavities can, for example, be hemispherical or they can have the shape of 
a flattened hemisphere. Other shapes that can be used are, for example, 
half ellipsoids or cylinders having hemispherical closed ends or flattened 
varieties thereof. 
In the International application, publication No. WO 83/03222, a device is 
described having a geometry of the above kind. In the publication it is 
mentioned that this device can be used for operations on margarines. 
It is essential in the present process that fraction (a) of the composition 
has been cooled such that part of the fat present in this fraction has 
been crystallized and is present in the solid phase when it enters the 
mixer to be mixed with fraction (b). Fraction (a) can suitably be cooled, 
for example by passing it through one or more scraped-surface heat 
exchangers. 
The composition used in the present process preferably comprises at least 
10% by weight of fat, the balance consisting essentially of material 
selected from the group consisting of water, protein, gas, emulsifiers, 
gelling and thickening agents, salt, flavour compounds, colouring matter 
and mixtures of two or more thereof. Other ingredients, e.g. 
preservatives, may, however, also be present in small amounts. 
Fraction (a) necessarily contains fat. Apart from this requirement, the 
compositions of fractions (a) and (b) and the ratios in which they can be 
mixed can be chosen in a variety of ways, as will be described below. 
In this application, by fat is meant, unless indicated otherwise, an edible 
substance, which may be solid or liquid at ambient temperature, consisting 
essentially of triglycerides such as, for example, soybean oil, sunflower 
oil, palm oil, coconut oil, fish oil, lard and tallow, which may have been 
partially or completely hydrogenated or modified otherwise, or comprising 
nontoxic material having physical properties similar to triglycerides, 
which material may be indigestible, such as for example waxes, e.g. jojoba 
oil and hydrogenated jojoba oil, and poly fatty acid esters of mono- and 
disaccharides, e.g. sucrose octa fatty acid ester, or mixtures thereof. 
The mixture leaving the mixer preferably is a dispersed system having a 
continuous fat phase containing crystallized fat. The mixture leaving the 
mixer can be packed immediately, e.g. by filling in tubs, or it can be 
subjected to further processing before packing it. Products that can thus 
be obtained are, for example, shortening, butter, margarines, low calorie 
spreads and melanges. By a low calorie spread is meant a product similar 
to butter or margarine, a product having a continuous fat phase and a 
dispersed aqueous phase and containing crystallized fat, but containing 
less than about 80% by weight of fat. By a melange is meant a product 
having a continuous fat phase and a dispersed aqueous phase and containing 
crystallized fat, wherein the fat comprises both butterfat and other fat. 
In the present process, preferably 10-99.99% fraction (a) is mixed with 
90-0.01% fraction (b), calculated as volume % on the total composition. 
Fraction (a) preferably comprises at least 20% by weight of fat. The 
amount of crystallized fat in fraction (a), when entering the mixer, is 
preferably at least 2%, more preferably from 5 to 60% by weight, 
calculated on the total amount of fat in fraction (a). 
In a preferred embodiment of the present invention, fraction (a) comprises 
at least 20% by weight of fat, fraction (b) comprises at least 5% by 
weight of water and 10-90% fraction (a) is mixed with 90-10% fraction (b), 
calculated as volume % on the total composition. Preferably, fraction (b) 
comprises 1 to 30% by weight of protein. It is also preferred that 
fraction (b) comprises from 10 to 85% by weight of fat. 
According to a preferred aspect of this embodiment, fraction (a) comprises 
at least 80% by weight of fat, fraction (b) is an aqueous solution or a 
dispersed system having a continuous aqueous phase and comprises at least 
30% by weight of water and 15-90% fraction (a) is mixed with 85-10% 
fraction (b), calculated as volume % on the total composition. For 
example, the present process is particularly suitable for preparing low 
calorie spreads, fraction (a) consisting mainly of fat and optionally 
containing other fat-soluble ingredients, such as emulsifiers and 
flavours, and fraction (b) providing the aqueous phase. The aqueous phase 
may contain gelling agents such as gelatin or guar gum and other 
water-soluble ingredients. Particularly when fraction (b) comprises a 
substantial amount of protein, e.g. milk protein, e.g. in the form of 
yoghurt or curd, excellent low calorie spreads can be prepared in this 
manner. 
A further advantage of preparing low calorie spreads in this manner is that 
the risk of formation of an oil-in-water emulsion instead of a 
water-in-oil emulsion is substantially reduced as compared to conventional 
processes. This is important because, especially in the preparation of 
very low fat spreads, containing e.g. less than 40% fat, it is a major 
problem to prevent phase inversion from occurring during the processing, 
which would result in a product having a continuous aqueous phase. 
To prepare low calorie spreads according to this aspect of the invention, 
preferably fraction (a) consists essentially of fat, fraction (b) 
comprises at least 40% by weight of water and at most 50% by weight of fat 
and 15-60% fraction (a) is mixed with 85-40% fraction (b), calculated as 
volume % on the total composition. 
Excellent products can be prepared if a cream comprising from 10 to 50% by 
weight of fat is used as fraction (b). Natural dairy cream can be used, 
but constituted creams, e.g. comprising vegetable fat, can also be used. 
Products thus prepared can have an improved texture, making a more creamy 
impression. This is probably caused by the partial retention of the 
structure of the cream in the final product such that the product is a 
double emulsion of the oil-in-water-in-oil type. 
Products such as margarine can be prepared by increasing the amount of 
fraction (a) that is used relative to the amount of fraction (b) and/or 
increasing the amount of fat in fraction (b). Products thus prepared can 
have improved properties as compared with products having the same 
composition but prepared in a conventional manner. 
According to another preferred aspect of this embodiment, the present 
invention provides a process wherein fraction (a) comprises from 20 to 90% 
by weight fat, fraction (b) comprises from 10 to 90% by weight fat, each 
of fractions (a) and (b) comprises from 5 to 80% by weight of water, from 
0 to 20% by weight of protein and from 0 to 20% by weight of other 
ingredients, and wherein both fraction (a) and fraction (b), when entering 
the mixer, have continuous fat phases. The protein content and the amount 
of other ingredients in each of the fractions are preferably at least 
0.05% by weight and 0.28% by weight, respectively. Preferably, both 
fraction (a) and fraction (b) comprise crystallized fat when entering the 
mixer. The amount of crystallized fat in each of the fractions preferably 
is at least 2%, more preferably 5-40% by weight of the total amount of fat 
in the fraction. 
It is particularly preferred that each of fractions (a) and (b), when 
entering the mixer, is margarine or butter or a low calorie spread. 
According to this aspect, for example margarine and butter can be prepared 
separately and then, optionally after storage, be mixed to provide a 
melange. Similarly, melanges can be prepared by mixing butter or a 
butterfat-containing low calorie spread with a low calorie spread 
containing fats other than butterfat. By mixing, for example, margarine 
with a low fat spread having a high protein content, excellent products 
can be prepared containing e.g. 60% fat. 
According to this aspect, substantially improved products can be obtained, 
because microstructural elements of each of the two fractions can be 
preserved during the mixing. 
When using other mixers, usually either an insufficient degree of mixing of 
the two products is obtained or the working conditions are so severe 
and/or the amount of heat dissipated so high that the microstructural 
elements of the separately prepared fractions are lost, so that all 
ingredients might as well have been mixed before the plastification. 
Another advantage is that the mixing can be achieved at relatively low 
pressure, even when mixing fractions as hard as butter. 
Particularly satisfactory products can be produced according to this aspect 
of the invention if churned butter or a low calorie churned 
butterfat-containing product is used as fraction (a) or (b). 
According to another preferred embodiment, the present invention provides a 
process wherein fraction (b) comprises a flavour compound, a precursor of 
such a compound or a microbial culture which produces a flavour compound 
or a precursor thereof. Preferably 90-99.99% fraction (a) is mixed with 
10-0.01% fraction (b), calculated as volume % on the total composition. 
For various reasons, it may be desirable to introduce minor components such 
as flavour compounds into the composition after plastification thereof. 
For example, some flavour compounds deposit in liquid oil, and it is 
therefore virtually impossible to get a homogeneous distribution in the 
product if such compounds are added in a premix vessel before 
plastification of the product. Moreover, such materials may deposit in the 
production line, which can cause contamination of the equipment. Such 
deposited material might then be incorporated in products which are 
subsequently produced with the same equipment. To prevent this from 
happening, additional cleaning would be required. With the present 
process, such compounds can be incorporated homogeneously without 
problems. Another advantage of the present process is that the risks of 
loss of flavour can be substantially reduced. 
Another example of particularly suitable application of this process is the 
preparation of butter. In this application, fraction (a), when entering 
the mixer, is sweet butter and fraction (b) comprises a microbial culture 
which produces a flavour compound or a precursor thereof and an edible 
acid. In this manner, high quality butter can be prepared and the 
buttermilk obtained is sweet instead of sour. 
Fraction (b) in this embodiment may comprise the minor components to be 
mixed in as such, but, preferably, fraction (b) is a dispersion or a 
solution of the minor components in water or fat. 
According to yet another preferred embodiment, fraction (b) comprises gas. 
The incorporation of gas can often improve the quality of a product; for 
example, its appearance can be improved. 
It is common practice to introduce the gas into the composition before 
plastifying it. With such a process it can be very difficult to obtain a 
proper distribution of gas bubbles, owing to uncontrolled expansion of the 
gas present in the composition after pressure has been released. Such an 
improper distribution of the gas adversely affects the quality of the 
product. With the present process, this problem can be overcome and gas 
can be homogeneously distributed in the product at relatively low pressure 
without substantially destroying the structure which has already been 
imparted to the remainder of the composition. 
Fraction (b) can be gas as such, e.g. nitrogen or air, but preferably 
fraction (b) is a dispersion containing gas, e.g. gas dispersed in a small 
amount of oil. 
Preferably, 40-98% fraction (a) is mixed with 60-2% fraction (b), 
calculated as volume % on the total composition. 
According to this process, products with a wide range of gas contents can 
be prepared. The gas content of the final product can be as low as 1 or 2 
vol. % or as high as e.g. 50-60 vol. %. 
Preferably, fraction (a) comprises from 60 to 100% by weight of fat. The 
process is particularly suitable for preparing gas-containing products 
such as shortenings.

SPECIFIC DESCRIPTION OF THE DEVICES 
In FIG. 1 is shown a mixer in longitudinal section. This comprises a hollow 
cylindrical stator member 1, a cylindrical rotor member 2 journalled for 
rotation within the stator with a sliding fit, the facing cylindrical 
surfaces of the rotor and stator carrying respective pluralities of 
parallel, circumferentially extending rows of cavities which are disposed 
with: 
(a) the cavities in adjacent rows on the stator circumferentially offset; 
(b) the cavities in adjacent rows on the rotor circumferentially offset; 
and 
(c) the rows of cavities on the stator and rotor axially offset. 
The pattern of cavities carried on the stator 3 and rotor 4 is illustrated 
in FIG. 3. The cavities 3 on the stator are shown hatched. The overlap 
between patterns of cavities 3, 4 is also shown in FIG. 2. 
The material passing through the device moves through the cavities 
alternately on the opposing faces of the stator and rotor. The cavities 
immediately behind those shown in section are indicated by dotted profiles 
on FIG. 1 to allow the repeating pattern to be seen. 
The material flow is divided between pairs of adjacent cavities on the same 
rotor or stator face because of the overlapping position of the cavity on 
the opposite stator or rotor face. 
The mixer can, for example, have a rotor radius of 2.5 cm with 36 
hemispherical cavities (radius 0.9 cm) arranged in six rows of six 
cavities. The internal surface of the stator can carry e.g. seven rows of 
six cavities to provide cavity overlap at the entry and exit. The material 
to be mixed is injected into the device through channel 5, which 
communicates with the annular space between the rotor and stator. The 
material leaves the device through exit 6. 
FIG. 4 shows elongate cavities arranged in a square pattern; these cavities 
have the sectional profile of FIG. 2. These cavities are aligned with 
their longitudinal axis parallel to the longitudinal axis of the device 
and the direction of movement of material through the device; the latter 
is indicated by the arrow. 
FIG. 5 shows a pattern of cavities having the dimensions and profile of 
those shown in FIGS. 1, 2 and 3. The cavities of FIG. 5 are arranged in a 
square pattern with each cavity being closely spaced from flow adjacent 
cavities on the same surface. This pattern does not provide as high a 
degree of overlap as given by the pattern of FIG. 3. The latter has each 
cavity closely spaced to six cavities on the same surface, in a hexagonal 
pattern. 
FIG. 6 shows a pattern of cavities wherein the cavities on the rotor, shown 
hatched, and stator have a larger dimension normal to the material flow; 
the latter is indicated by an arrow. The cavities are thus elongate. This 
embodiment can provide a lower pressure drop over its length compared with 
devices of similar geometry but not having cavities positioned with a 
longer dimension normal, i.e. perpendicular to the material flow. To 
obtain a reduction in pressure drop, at least one of the surface must 
carry elongate cavities having their longer dimension normal to the 
material flow. 
EXAMPLES 
Example 1 
A protein-containing low calorie spread was prepared as follows: 
The fat phase was prepared by mixing 
20 wt. % soybean oil 
19 wt. % rapeseed oil 
10 wt. % palm oil 
23 wt. % soybean oil hydrogenated to a slip melting point of 36.degree. C. 
26,75 wt. % fish oil hydrogenated to a slip melting point of 35.degree. C. 
1 wt. % emulsifiers 
0.25 wt. % colouring matter. 
The aqueous phase was prepared by mixing 
84 wt. % water 
14 wt. % sodium caseinate 
1.5 wt. % salt 
0.5 wt. % other ingredients. 
The fat phase was heated to 45.degree. C. and plastified at a capacity of 2 
kg/h by passing it through a scraped-surface heat exchanger of the Votator 
type (A-unit), subsequently passing it through an agitated crystallizer of 
the Votator type (C-unit) and passing it through another A-unit, The 
pressure at the beginning of the line was 14 bar absolute. The plastified 
fat phase leaving the second A-unit had a temperature of 10.degree. C. and 
contained 27% by weight of crystallized fat. 
The aqueous phase was cooled down from 45.degree. C. to 9.degree. C. by 
passing it through an A-unit at a capacity of 3 kg/h. 
The product streams of plastified fat and cooled aqueous phase were both 
passed into a mixer of the type shown in FIG. 1, at a total capacity of 5 
kg/h. The density of the plastified fat phase was about 0.9 g/ml, that of 
the aqueous phase was about 1 g/ml. The pressure drop across the mixer was 
about 2 bar. 
The product leaving the device was filled into tubs. Its temperature was 
13.5.degree. C. 
The diameters of the stator and rotor of the mixer were 28 mm and 27.7 mm, 
respectively, providing an annulus of 0.15 mm. The number of cavities on 
the stator was 36 and on the rotor 42. Each cavity had a diameter of 12 mm 
and a depth of 4 mm. The volume of the mixer was 50 ml. The rotor speed 
was 200 rpm. 
A good quality product was obtained having hardness values (C-values) at 
10.degree., 15.degree. and 20.degree. C. of 1230, 650 and 220 g/cm.sup.2, 
respectively. The hardness of the product was measured with a cone 
penetrometer as described in J.A.O.C.S. 36 (1959), 345-348. The product 
had a homogeneous droplet dispersion. 
Similar results were obtained when the rotor speed of the mixer was 1000 
rpm instead of 200 rpm. 
Example 2 
Example 1 was repeated using an aqueous phase having the following 
composition: 
99.7 wt. % water 
0.2 wt. % salt 
0.1 wt. % potassium sorbate. 
A proper low calorie spread was obtained. 
Example 3 
A product having an oil-in-water-in-oil structure was prepared by using a 
fat blend as fraction (a) and a cream as fraction (b). 
Fraction (a) was prepared by mixing the following ingredients: 
55 wt. % rapeseed oil 
5 wt. % palm oil 
22 wt. % hydrogenated fish oil (smp 37.degree. C.) 
18 wt. % hydrogenated soyabean oil (smp 36.degree. C.) 
0.3 wt. % emulsifiers 
0.2 wt. % colouring matter. 
A cream was prepared from the following ingredients: 
40 wt. % water 
53 wt. % sunflower oil 
3 wt. % soured skimmed milk 
2.3 wt. % milk protein 
0.5 wt. % salt 
0.5 wt. % gelatin 
0.5 wt. % preservatives 
The fat blend was heated to 45.degree. C. and plastified by passing it 
through an A-unit, a C-unit and an A-unit as described in Example 1, at a 
capacity of 2.2 kg/h. The plastified fat blend leaving the second A-unit 
had a temperature of 5.degree. C. and a solids content of 15% by weight. 
The pressure before the first A-unit was 14 bar absolute. 
The cream was cooled to 10.degree. C. and 1 kg/h of cream was passed 
together with the stream of plastified fat through a mixer as described in 
Example 1. The relative amounts in which the fat and the cream were mixed 
were about 69 volume % fat and about 31 volume % cream. The pressure drop 
across the mixer was 0.5 bar. The product leaving the mixing device was 
packed. 
An excellent product with a homogeneous droplet dispersion was obtained, 
which made a very creamy impression. This was in agreement with analysis 
of the product which showed that it contained 31.6% internal phase. Thus, 
essentially all oil contained in the cream was retained inside the aqueous 
droplets in the end product. 
The oral melt properties of the product were satisfactory: the salt release 
(T 100=temperature at which the emulsion is completely destabilized) was 
37.6.degree. C. 
The example was repeated using a rotor speed of the mixer of 1000 rpm. The 
product obtained comprised 28% internal phase. It has a T 100 salt release 
value of 37.6.degree. C. 
Example 4 
A product was prepared by using both as fraction (a) and as fraction (b) a 
plastified product having a water-in-oil structure and containing 
crystallized fat. 
Fraction (a) had the following composition: 
35 wt. % palm oil 
10 wt. % soybean oil 
23 wt. % rapeseed oil 
16 wt. % hydrogenated soybean oil (smp 36.degree. C.) 
16 wt. % water 
0.3 wt. % emulsifiers. 
Fraction (b) contained the same ingredients as fraction (a) and further 
contained 0.2% by weight of a solution of 0.4% by weight of 
.beta.-carotene in oil as colouring agent. 
Margarine was prepared from fraction (a) in a conventional manner, at a 
capacity of 27 kg/h. 
Fraction (b) was plastified in the same way as fraction (a). 
Subsequently, 50% fraction (a) and 50% fraction (b), calculated as volume % 
of the total composition, were led into a mixer as described in Example 1, 
at a total capacity of 54 kg/h. When entering the mixer, fractions (a) and 
(b) contained 8% crystallized fat, calculated as % by weight on the total 
amount of fat of each fraction. The rotor speed of the mixer was 100 rpm. 
The product leaving the mixer was packed. 
The example was repeated once with a rotor speed of 200 rpm and once with a 
fixed rotor (rotor speed 0 rpm). The example was repeated at rotor speeds 
of 0, 100 and 200 rpm using a total capacity of 38 kg/h (19 kg/h of each 
of fraction (a) and fraction (b)). 
Some properties of the products obtained, determined 15 minutes after 
production, are shown in Table I. 
TABLE I 
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total capacity 
54 54 54 38 38 38 
(kg/h) 
rotor speed 
0 100 200 0 100 200 
(rpm) 
temperature 
15 16 16 17 15 16 
(.degree.C.) 
solids content 
12 17 14 18 18 13 
(wt. %) 
hardness 1400 1150 1300 2000 1400 1500 
(g/cm.sup.2) 
colour* 2 1 1 2 1 1 
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*colour: 
1 indicates a product having a homogeneous colour 
2 indicates a product having a nonhomogeneous colour 
The results in the table show that at a rotor speed of 0 rpm, i.e. when 
using the device as a sort of static mixer, a product is obtained which 
has a nonhomogeneous colour. The experiments carried out at rotor speeds 
of 100 rpm or 200 rpm show that, even when using fractions (a) and (b) 
that have both been plastified, a sufficient degree of mixing can be 
obtained with a rather small mixer, used at a high capacity. 
Example 5 
A product containing 50 volume % of air was prepared from a fraction (a) 
containing the non-gaseous ingredients and a fraction (b) consisting of 
air. 
Fraction (a) was prepared from the following ingredients: 
84 wt. % of the fat blend described in Example 1 
11 wt. % water 
5 wt. % soured skimmed milk 
0.1 wt. % colouring matter 
0.1 wt. % salt 
0.1 wt. % potassium sorbate. 
Fraction (a) was homogenized at 44.degree. C. in a premix vessel. The 
mixture was then passed at a capacity of 2.1 kg/h through an A-unit, a 
C-unit and another A-unit. The mixture left the second A-unit at a 
temperature of 7.5.degree. C. It was a water-in-oil emulsion which 
contained 23% of crystallized fat, calculated as weight % on the total 
amount of fat. 
50 volume % fraction (a) leaving the second A-unit was fed with 50 volume 
of air into a mixer as described in Example 1. The mixer was operated on 
an overall capacity of 2.1 kg/h and a rotor speed of 800 rpm. The pressure 
drop across the mixer was 1 bar. 
The product leaving the mixer was packed. It left the mixing device at a 
temperature of 19.5.degree. C. and it contained 12.2% crystallized fat, 
calculated as % by weight on the total product. 
The hardness of the product at 5.degree., 10.degree. and 15.degree. C. was 
2050, 1800 and 1030 g/cm.sup.2, respectively. The gas was dispersed very 
homogeneously throughout the product. The appearance of the product was 
excellent; it had a pale, mat surface. The Yellowness Index was 31, the 
Gloss (Intensity of light reflected by the surface of a beam illuminating 
the surface under an angle of 60.degree. C., expressed as % of the 
intensity of the illuminating light beam) was 9.5. 
Examples 6 and 7 
Two melanges were prepared from fat blends containing respectively 25 and 
50 wt. % of butter, and respectively 75 and 50 wt. % of margarine, but 
separately feeding the two products to a mixer as described in Example 1. 
The rotor speed was 750 rpm, and the feed temperature of both feed streams 
was 8.degree. C. The solid fat content of the butter was 52 wt. % and of 
the margarine was 47 wt. %. The temperature of the products leaving the 
mixer was 9.degree. C. The product characteristics are given in the table. 
TABLE 
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Example 6 7 
wt. % butter 25 50 
C10 1100 1300 
C20 90 60 
______________________________________ 
The products obtained could be spread very good, and had better properties 
than each of the starting products as such.