Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
This invention relates generally to processes for the commercial manu-
facture of fat-containing dry milk or flavored dry milk in the form of aggre-
gates which can be readily dispersed in water to form a stable reconstituted
milk. Also it pertains to products resulting from such processes.
So-called instant dry milk is widely manufactured and sold in the
United States and other countries. As disclosed in Peebles United States
Patent 2,835,586, dated May 20, 1958, the process involves supplying nonfat
anhydrous dry milk powder to an agglomerating chamber where the particles are
moistened and commingled to cause formation of random porous aggregates.
These aggregates, which in typical instances may have a total moisture cont-
ent of the order of from 10 to 15%, are thensubjected to secondary drying to
remove excess moisture. Such instant nonfat dry milk can be readily recon-
- stituted with cold water by simple stirring and without vigorous agitation.
The process of said Patent 2,835,586 can be used to agglomerate spray dried
fat-containing dry milk as well as spray dried nonfat dry milk powder. How-
ever, instant fat-containing milk made in this fashion has impaired wettabil-
ity and dispersibility in water, and the reconstituted milk is subject to
fat separation.
Subsequent to the development of the above Peebles process, it was
found that an acceptable fat-containing agglomerated dry milk could be formed
- by the use of lecithin. As described in United States Patent 3,164,473,
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dated January 5, 1965, lecithin is supplied in such a fashion that in the
final agglomerated product, it is in the form of extraneous lecithin distri-
buted on the powder particles and agglomerates. The use of lecithin as des-
cribed in said Patent 3,164,473 makes it possible to produce a fat-containing
instant dry milk which can be reconstituted in cold water. However, it makes
use of fat-containing spray dried milk powder as a source material. An im-
proved process making use of the process of United States Patent 3,164,473
dated January 5, 1965, is disclosed in United States Patent 3,300,315 dated
January 24, 1967. The improved process like wise makes use of fat-containing
milk as a source material. The liquid fat-containing milk is spray dried
to form a moist powder which is passed through an agglomerating chamber into
which a mixture of steam, water and lecithin is introduced. The resulting
aggregates, after removal of excess moisture, having relatively good disper-
sibility in cold water. The processes of Patents 3,164,473 and 3,300,315
have been used for the commercial manufacture of acceptable instant dry milk
products having a fat content of the order of 5%. However, plants using such
processes require high captial investment in central locations (e.g., for
evaporators, spray dryers, instantizers, etc.) and involve high transpartation
costs when the product is distributed nation-wide.
United States Patent 2,911,300 dated November 3, 1959, proposes
to produce a dry instant milk product containing fat by first forming nonfat
milk solids in the form of aggregates, and after drying to remove excess
moisture, fat in molten form is applied to the surfaces of the aggregates.
As pointed out in said Patent 2,911,300,
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such a product can be dissolved in warm water. The patent further proposes
the use of a fat-water emulsion of the type disclosed in Peeble et al. United
States Patent 2,622,984 dated December 23, 1952, which consists of fat and
water together with a soluble caseinate. This mixture is subjected to homo-
genizing as ordinarily applied in the milk industry, after which it is applied
to the aggregates and the aggregates dried to remove excess moisture. Pat-
ent 2,911,300 also refers to the use of lecithin as an emulsifier in prepar-
ing the emulsion of Patent 2,622,984, in place of part or all of the case-
inate content. While the process of Patent 2,911,300 makes use of nonfat
- 10 milk solids as a source material, it separates the aggregating step from the
step of applying the fat emulsion. Since some moisture is added with the
fat, the moisture content of the aggregates is increased, thus requiring
another stage of secondary drying. This process is subject to other diffi-
culties, particularly in that some fat separation tends to occur in the
reconstituted milk, and the amount of separating fat increases for the high-
er fat contents.
Summary of the Invention and Objects
In general it is an object of the present invention to provide a
process for the manufacture of fat-containing instant dry milk which carries
out an agglomerating operation and the application of fat in a single step.
Another object is to provide a process which produces instant fat-
containing milk of acceptable quality uhich can be readily reconstituted
with warm or cold
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water to form a stable reconstituted milk, is not subject
to objectionable fat separation for a wide range of fat
contents, and which has good flavor characteristics.
Another object is to provide a process in which
high pressure homogenization is employed to prepare a fat
emulsion having relatively small fat globules of less than
3 microns, the homogenization being under such conditions
as to minimize reversal of the emulsion phase (i.e.,
demulsification) with resulting fat churning.
Another object is to provide an instant fat-
containing dry milk which has its fat content in the
form of relatively small globules of micron size and
intimately associated with the aggregates, with the leci-
thin or like wetting agent being incorporated in such a
manner as to be effective in promoting wettability and
. dispersibility of the product.
In general, the process of the invention consists
in supplying anhydrous dry milk powder to an agglomerating
chamber and causing the powder to be dispersed therein. In
addition to supplying the powder, atomized material is supplied
to the chamber, the material consisting of atomized lecithin
and atomized fat-water emulsion. The atomized lecithin is
supplied together with steam. The atomized fat-water emulsion
is such that the bulk of the fat globules have a size of the
order of 3 microns. The atomized lecithin and steam is supplied
; separately from the atomized fat-water emulsion. Within the
agglomerating chamber the atomized materials are commingled
with the dispersed powder particles within the chamber whereby
the powder particles are caused to adhere together in the form
of porous random aggregates with the fat and lecithin simul-
taneously being applied to and distributed on the particles and
the aggregates. The fat thereby supplied serves to substantially
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increase the fat content of the aggregates. Excess moisture
is removed from the aggregates to form the final dry product.
The lecithin content is preferably of the order of 0.17 to
0.6% in the final product. The fat-water emulsion is subjected
to high pressure homogenization to produce a material having
fat globules of a size of the order of less than 3 microns.
The fat-water emulsion may consist of dairy cream with added
nonfat milk solids. Preferably such an emulsion is heat
treated to a temperature of 170 - 190F for a period of
5 - 15 minutes to improve the flavor.
Additional objects and features of the invention will
; appear from the following description in which the preferred
~ embodiments have been set forth in detail in conjunction with
- the accompanying drawing.
Figure 1 is a diagram illustrating one procedure for
carrying out the process.
Figure 2 is a diagram illustrating another procedure ~;
for carrying out the process.
Figure 3 schematically illustrates suitable apparatus
for carrying out the process.
Figure 4 schematically illustrates apparatus for pre-
- paring material that is supplied to the agglomerating chamber, and
the means associated with the agglomerating chamber for dispersing
material into the agglomerating chamber.
The process as illustrated in Figure 1 makes use of
anhydrous spray dried milk powder as the source material, and dairy
- cream as a source of fat. Dairy cream normally contains water, fat,
protein and some lactose. The water content may vary from about 54
to 58%, the fat from 38 to 42%, the protein from 2 to 2.5%, and
the lactose from 2.8 to 3.4%. A typical cream is an emulsion con-
taining about 56% water, 39% fat, 2.2% protein, and 3.1% lactose,
with an ash content of about
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0.4%. Before subjecting the cream to homogenizing step 11 to reduce the
size of the fat globules, it preferably is mixed in step 10 with one or more
agents which serve the purpose of preventing reversal of the emulsion phase
with fat churning under relatively high homogenizing pressures. Agents which
have been found suitable for this purpose are certain emulsifiers having such
characteristics that they will not impair the flavor and quality of the final
product. Satisfactory emulsifiers are those selected from the group compris-
ing mono and diglycerides of long chain fatty acids, and ethoxylated mono
and diglycerides of long chain fatty acids, or combinations thereof having a
10 melting point below about 180F. (e.g., within the range of 85 to 180F.).
In practice, we have obtained good results by using a mixture of ~rom 10 to
25% (optimum 17%) of distilled mono-glycerides and from 90 to 75% (optimum
83%) of ethyoxylated mono and diglycerides at a level of from 1 to 3% (opti-
mum 1.5%) of the butterfat. These materials together with the cream are
blended at a temperature (e.g., 180F.) above the melting point of the emul-
sifiers.
- An additional material which serves in conjunction with the emulsifier
to prevent reversal of the emulsion phase in the homogeni7ing step 11 is non-
fat milk solids, which can be added to the cream in step 10 as indicated.
The amount of nonfat milk solids added at this point is in accordance with
the fat content of the cream. It may range from an amount (by weight) equal
to the amount of fat, to one fourth the amount of fat.
; Introduction of milk solids in step 10 for mixing with the cream can
be facilitated by first dispersing the milk solids in water and then blending
the resulting reconstituted milk with the cream. For example, the amount
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of milk solids dispersed in water can be such as to provide a concentrate
consisting of 40 to 50% solids. The total amount of moisture in the mix
should be consistent with the moisture requirements for the agglomerating
operation.
For the purpose of promoting storage stability, small amounts of
an antioxidant may be added to the cream, based on the fat content. The
cream may also serve as a carrier for nutrient fortification, as for example,
such nutrients as vitamins A and D.
The mixture produced in step 10 at a temperature of about 145 to
150F. is supplied to the homogenizing step 11 where it is homogenized at
relatively high pressures, such as at a pressure of 2500 to 3500 psig for
the first stage and 500 psig for the second stage. Homogenization at such
pressures serves to greatly reduce the size of the fat globules whereby
the bulk of the globules have a size of the order of less than 3 microns.
Normally the use of such high homogenizing pressures tends to reverse the
emulsion phase with release of free fat and fat churning. However, when the
emulsifier is present it appears that this phase reversal does not take place
or is minimized, and therefore there is a minimum amount of free fat in the
homogenized material. Nonfat milk solids present in the mixture also play
a part in preventing such phase reversal. According to our observations
this is due to association of the protein content of the nonfat milk solids
` with the enrobement of the fat globules.
After being homogenized in step 11, the fat emulsion mixture is
supplied to the agglomerating step 12 where it is dispersed in atomized form
and the atomlzed droplets caused to commingle with particles of dry milk
powder being continuously supplied to the agglomerating
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chamber. A spray dryer type of atomizing nozzle can be used, with the fat
emulsion mixture being supplied to the nozzle at pressures of the order of
1500 to 4000 psig (2000 psigoptimum). Water vapor and steam are likewise
dispersed in the agglomerating chamber whereby sufficient moisture is present
in the agglomerating chamber to cause moistening of the powder particles
with agglomeration of the particles together. In the agglomerating step the
atomized and agglomerated fat mixture becomes intimately associated with the
powder particles and the resulting aggregates.
Lecithin or lecithin product is supplied to provide a wetting agent
which increases we~tability and dispersibility of the final product in cold
water. It is introduced into the agglomerating step 12, separate from the
homogenized fat mixture. Thus, as indicated in Figure 1, the lecithin may
be supplied to a mixing device 13 where it is intermixed with steam being
supplied to the agglomerating chamber. When introduced in this manner the
lecithin maintains its effictiveness in promoting wettability and dispersibil-
ity of the final product. When lecithin is mixed or homogenized with milk
protein such as is present in cream and nonfat milk solids, the protein tends
to enrobe the lecithin, thus blocking its wetting abilities.
The agglomerating step can be carried out in an agglomerting chamber
; 20 of the type disclosed in said U.S. Patent 2,835,586, or equipment as disclosed
in United States Patent
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3,311,306 dated July 18, 1967. The aggregates discharging from the agglomer-
ating chamber in a typical instance have a total moisture content ranging from
about 9 to 14% (11 to 12% optimum). A substantial part of this moisture is
derived from the cream mixture, and the remainder may be derived from the
condensed steam. The final or secondary drying step 14 can be carried out
by the procedure described in said Patent 3,300,315 to produce a final dry
product of the desired moisture content ~e.g., 1 to 2%).
As pointed out in said Patent 3,300,315, lecithin is the commercial
or popular name for a crude mixture of compounds which may be more accurately
designated as phosphatides or phospholipids. The phosphatides are complex
organic compounds which are similar to fats or lipids but differ from fats
radically enough to give them unique properties. Lecithins of vegetable oil
origin are mixtures of phosphatides produced from such raw materials as cot-
tonseed oil, corn oil, or soybean oil. Products from current commercial
treatments which modify natural lecithin to emphasize either the lipophilic
groups or the hydrophilic groups may be used. Commercially available soya
lecithin has been used with good results. It is commercially available as
a liquid material with lecithin dispersed in a soybean oil carrier. Assuming
that the liquid lecithin product contains about 60% lecithin to obtain a
final product containing from say 0.17 to 0.6% lecithin, from 0.25 to 1% of
such a lecithin product can be employed.
~- The use of steam in conjunction with atomizing
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the mixture supplied to the agglomerating chamber is desirable in that it
provides an elevated temperature which facilitates formation of aggregates,
and in addition, it aids effective atomization with uniform distribution of
the atomized material upon the powder particles and provides some of the mois-
ture. Also when lecithin is introduced with the steam it is effectively
dispersed and caused to be incorporated with the aggregates as a separate
material. In general, it is satisfactory to supply culinary steam at a suit-
able pressure ~e.g., 120 psi).
At the lower fat levels ~e.g., 10% or less) it is desirable to supply
anhydrous nonfat milk powder to the agglomerating step 12. Thus all of the
fat of the final product is supplied to the agglomerating step l2 by way of
the homogenized mixture from step 11. This simplifies commercial processing
because nonfat spray dried milk is not subject to flavor or quality deterior-
ation when stored and shipped in sealed containers without the use of nitro-
; gen or other inert gas. For the higher fat levels in the final product ~e.g.,
10 to 28%) it is desirable to make use of some anhydrous fat containing milk
produced by spray drying, thereby reducing the amount of fat which is added
in the agglomerating operation 12 to attain the desired fat level in the fi-
nal product. By way of example, assuming that a final fat level of 28% is
desired, the spray dried milk supplied to the agglomerating step 12 may have
a fat content of 25% and the amount of fat added by way of the homogenized
mixture from step 11 may serve to raise the fat content of the final product
to the desired 28% level.
Instead of making use of a spray dried milk powder
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having a fat content which is somewhat less than that desired in the final
product, a desirable procedure is to utilize spray dried whole milk ~28% fat)
and blend the same with nonfat spray dried milk, whereby a blend is supplied
to the agglomerating step 12. The blended material has a fat content some-
what less than desired in the final product. The amount of homogenized mix-
ture from step 11 added in the agglomerating step 12 is sufficient to raise
the fat to the desired level in the final product. Spray dried whole milk
;; is generally more commercially available than a spray dried milk of lower
fat content, and in addition, the use of such a blend facilitates agglomera-
tion at higher fat levels in the finished product.
Irrespective of whether or not the dry milk powder has a fat content,
` is a blend of fat-containing milk with nonfat spray dried milk, or nonfat
spray dried milk, it it desirable for it to have a relatively low solubility
index, as for example, an index of the order of 0.1 or less. A low solubility
index indicates a minimum amount of denaturation of the heat coagulable pro-
tein of the milk. When the protein is denatured to a substantial extent, it
tends to settle out in the reconstituted milk, thus impairing its quality
as a beverage. It should be understood, however, that the process of the
present invention can be used with milk having a solubility index in excess
of 0.1. Processing according to the present invention does not appreciably
increase the solubility index of the original powder.
A typical sieve analysis of a product made according to the present
invention, with a fat content of
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5% (dry solids basis) is as follows:
Mesh Streen
~U.S. Standard) Percent
On 80 54.5
On 100 25.0
Through 100 20.5
The pour bul~ density of a typical product made
i~ accordance with the proce~s described above is of
the order of 0.20 to 0.30 grams per milliliter. A pour
bul~ density of 0.27 is typical of a product having the
abo~e sieve analysis and having a f~ content of 5~ ~dry
solids basis). The product produced as described above
has good wettability and can be readily dispersed in
cold water (e.g., 68F.) by simp;e stirring to form a
stable reconstituted milk. Thus, when a quantity is
introduced into cold water to form a reconstituted milk,
simple stirring with a spoon for a period of the order
of 10 to SQ seconds suffices to completely disp~erse the
mater~al. Assuming the source milk powder has a protein
content that is not seriously denatured by heat treat-
ment, the reconstituted milk is stable in that no substan-
tial settlement of solids occurs when the milk is permitted
to stana for extended periods of the order of 24 hours
or more.
- 25 A characteristic of products made according to
the foregoing process is that when reconstituted with cold
water and ~ermitted to stand for periods of the order of 24
hours or more, there is minimal or no noticeable separation
of fat or cream at the surface of the liquid. This is true for
products having a relatively low fat level, as for example,
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5%, and also products having a relatively high fat level of the order of
28%. We attribute this to certain features of the process, including the
presence of the emulsifier at the time the cream is homogenized in step 11.
As previously explained, this serves to permit homogenization at relatively
high pressures with production of relatively small fat globules without phase
reversal. Absence of fat separation is attributed not only to the presence
of the emulsifier at the time the mix is homogenized, but also the presence
of added nonfat milk solids. Good wettability and dispersibility of the
product is attributed not only to the physical character of the aggregates,
but in addition, to the fact that the lecithin remains separate from the fat,
and therefore is present in such form as to be most effective as a wetting
agent. As previously mentioned, when lecithin is added before the homogeniz-
; ing step 11, nonfat milk components present, including nonfat milk solids
added in step 10, tend to enrobe the lecithin, thereby blocking its wetting
abilities in the final product. This enrobing or blocking effect does not
; take place when the lecithin is introduced into the agglomerating chamber to-
gether with the steam.
r~`; The apparatus for carrying out the process shown in Figure 3 consists
of a cyclone feed chamber 25 together with a treatment or agglomerating cham-
ber 26. The cyclone chamber corresponds generally to that of a conventional
pneumatic cyclone, and is shown consisting of the upper cylindrical portion
25a and the lower conical shaped portion 25b. A feed supply conduit 27 con-
nects
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tangentially with the upper portion of the chamber, and an exhaust conduit 28
communicates with the central region of the cyclone chamber and serves to
remove air from which powder has been centrifugally separated.
The treatment chamber 26 is shown provided with an upper cylindrical
shaped portion 26a together with a lower conical shaped portion 26b. The
chamber 26 is in direct ccmmunication with the lower end of the cyclone
through the coupling conduit 33. It will be noted that the cyclone and the
treatment chamber 26 are in axial alignment.
The means employed for introducing a fluid mixture in atomized form
may be as illustrated in Figure 4. It consists of a spray nozzle 35 attached
to the lower end of the supply pipe 36. The portion of the pipe 36 extending
immediately above the nozzle is enclosed within the jacket 37. One portion
of this jacket is connected by pipe 38 wlth a source of cool air under pres-
sure and the lower end of the jacket is provided with openings 39 from which
air is discharged into a region generally surrounding the nozzle 35.
- During operation of the apparatus, jacket 37 serves the purpose of
- preventing contact between the powder being treated and the pipe 36 which,
under certain operating conditions, might cause accumulation of solid mater-
ial. Also the downwardly directed air jets discharging from apertures 39
; 20 into the region surrounding the nozzle 35 tend to prevent back swirl and~ac-
cumulation of solid material on the nozzle.
The nozzle 35 shown in Figure 4 consists of a
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body 40 which is attached to the pipe 36. It has an orifice 41 and a diver-
gent passage 42 extending from the oriice. A nozzle of this type serves to
direct a divergent conical shaped spray into the treatment chamber. The noz-
zle 35 is within the upper portion of the treatment chamber, and it is gener-
ally aligned with the central vertical axis of the chamber.
Conventional means can be used for supplying dry milk powder together
with an airstream to the conduit 27 (Figure 2). As illustrated schematically
in Figure 2, the conduit 27 may connect to the discharge side of blower 46.
A powder hopper 47 communicates with the inlet conduit 48. A powder feed
means 49, such as one of the feedscrew type, serves to deliver powder at the
desired regulated rate to the hopper 47.
The treated material in the form of moist porous aggregates drops by
'` gravity through the lower end 51 of the treatment chamber 26. As shown in
Figure 2, the discharge opening 51 is shown delivering the moist material
directly to the dryer 52. This dryer can be of the shaker type consisting
of a main body 53 which has an inlet end 56 coupled directly to the lower end
of the treatment chamber. Warm dry air is introduced below the screen thro-
ugh conduit 57. Air is removed from the space over the screen by the hood
58 and conduit 59. The flexible cloth walls 60 couple the lower end of the
hood to the upper side of the body 53. It will be understood that two or
more stages of such drying units can be used as desired.
The upper part of chamber 26 is shown connected
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by chamber 61 and conduit 62 with a suction fan 63. This conduit also con-
nects with the exhaust conduit 28. By adjusting the damper 62a, a controlled
amount of cool atmospheric air may be drawn into the lower opening 51, thus
causing the downwardly falling aggregates to be enveloped in upwardly moving
temperate air.
The walls of chamber 26 can be kept at a temperature corresponding
generally to the mean temperature of the atmosphere within the same. Thus,
these walls may be covered by heat insulating material, or they may be pro-
vided with a jacket 64 connected with the hot air supply conduit 56a and the
discharge conduit 65b. With this arrangement, warm air can be circulated
through the jacket to maintain the walls of the chamber 26 at a desired temp-
erature level.
Figure 4 shows means for supplying the nozzle 35 with lecithin which
is to be atomized and dispersed in the agglomerating chamber. It consists
of a mixing device 66 having a tapered discharge and connected to line 36. -~
The hollow body has an inner tube 67 which connects with the incoming line
68. Also the body has a side inlet which connects with the incoming line 69.
Swirl fins or vanes 70 are shown within the tapered portion of the body.
Line 68 connects with suitable means, such as a metering pump, which is cap-
able of supplying the lecithin product at a predetermined controlled rate.
Line 69 connects with a source of steam as illustrated, and a mixer 71 con-
nected with a source of water as indicated by line 72 may be connected in
this line.
As illustrated in Figure 4, an additional
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nozzle 74 is provided alongside the nozzle 35. This may be a high pressure
atomizing nozzle such as is commonly used in milk spray drying equipment.
Pipe 75 connects with nozzle 74 and is supplied with the homogenized mix from
the homogenizing step 11. A suitable high pressure pump supplies the mater-
ial to pipe 75 at a relatively high pressure of the order of 1500 to 4000
psig. Atomizing nozzle 74 produces a divergent spray through which the down-
wardly moving powder passes, with the spray being commingled with lecithin
an~ water vapor being sprayed downwardly by the nozzle 35. Thus the powder
particles commingle with the homogenized fat-containing mixture produced in
atomized form by the nozzle 35, while at the same time the powder particles
are commingled with droplets of lecithin dispersed by the steam, and the ste-
am and isture present in the fat emulsion create a humid atmosphere within
the agglomerating chamber.
Operation of the arrangement shown in Figure 4 is as followsO Steam
at constant pressure Ce.g., 120 psig) is supplied to the line 69, and the
lecithin product in liquid form is supplied through line 68 at a predetermined
constant rate. The steam supplied by way of line 69 is caused to be inter-
- mixed with the lecithin by virtue of the swirling action induced by the vanes
70. As a result a relatively homogeneous mixture of lecithin and steam is
delivered through line 36 to nozzle 35. Some water can be introduced together
; with the steam by controlled admission through line 72, depending upon the
moisture and temperature requirements within the agglomerating chamber.
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Figure 2 illustrates another embodiment of the process in which the
cream mixture is subjected to heat treatment 15 for flavor improvement. Thus
as in the process of Figure 1 the emulsifier together with milk solids and
cream are supplied to the mixing step 10 where the mixture is heated to 170
to 190F. ~180F optimum) and held at this temperature for 10 minutes.
Thereafter the material is cooled to 145 to 150F. and homogenized in step 11,
as in Figure 1. The agglomerating step 12 is carried out in the same manner
as in Figure 1, and as indicated, the milk powder being supplied to the agglo-
merating step is a blend of spray dried fat-containing powder (e.g., whole
milk powder) and nonfat milk powder. The remainder of the process as shown in
Figure 2 is the same as in Figure 1. As indicated in Figure 2, a small amount
of an anti oxidant (e.g., 0.05% fat basis Tenox 7) may be added to the cream
together with the emulsifier in mixing step 10.
As described above, cream is used as a source of fat. However, in
place of using dairy cream it is possible to use butter oil together with
sufficient nonfat dry milk powder and water, whereby the material after being
homogenized in step 10 has the desired fat milk solids and water contents
comparable to cream for use in the agglomerating step 12. While the products
made by use of butter oil are of good quality, it has been our observation
that the flavor is slightly different from products made with dairy cream,
which is attributed to the relatively strong butter flavor of the butter oil.
Also other fats can be used in place of butterfat. Such fats should be edible,
relatively free from free fatty
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acids, and may have melting points of the order of 70
to 120F. Butterfat has a melting point of the order of
90F. For example, reference can be made to any one
of a number of edible hydrogenated vegetable oils or fats
S such as hydrogenated coconut, cottonseed, peanut and corn
oils having melting points of the order of 70 to 120F.
~hen making use of such vegetable fats, an emulsion or cream
i8 prepared in step I0 by mixing the fat with a suitable
amount of water and emulsifier at a temperature above the
me?ting point of the fat. Also some milk solids can be
added to the mixture, the same as when using dairy cream.
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Examples of the process are as follows:
Example l.
In this example a product was prepared having a fat level of 5%. The
procedure was generally as illustrated in Figure 1. The source material was
commercial spray dried anhydrous nonfat milk powder having a bulk density of
about 612 grams per liter and a total moisture content of about 2%. The
solubility index was about 0.1. This powder was fed pneumatically at a met-
ered rate to an agglomerating chamber as shown in Figure 3. A good quality
edible fresh dairy cream analyzing 40% butterfat was adjusted to a fat level
of 22.5% fat and 45% total solids by the addition of nonfat dry milk powder
reconstituted in water. To this cream there was added 1.5% of emulsifier
(on a fat content basis), the emulsifier being a blend consisting of 16.67%
monoglycerides and 83.33% ethoxylated mono and diglycerides. The resulting
mixture was heated to 180F., held at that temperature for 10 minutes and
then cooled to 145 - 150F. The mixture was then passed through a commercial
homogenizing equipment, the first stage being at a pressure of 3000 psig,
and the second stage at 500 psig. Homogenization was carried out at a temp-
erature level of 145 to 150F. The nonfat milk solids were pneumatically
conveyed into the agglomerating chamber. The homogenized cream mixture was
pumped to the atomizing nozzle 74 at a pressure of 1500 to 2000 psig, the
rate being consistent to produce the desired fat level in the final product.
A soybean-lecithin product was metered into the steam line 69 at a rate to
attain a 0.6% lecithin level in the
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final product. The amount of steam added was sufficient to control the
moisture level of the aggregates leaving the agglomerating chamber at a total
moisture level of about 10 to 11%. The moist agglomerated material was then
dried to a moisture content below 2%.
The resulting instant fat containing milk product was of excellent
quality with a pore density of 0.27 grams per milliliter. When subjected to
the wettability test as disclosed in United States Patent 3,231,386, the
wettability proved to be excellent, the powder sinking in cold water within
a period of 15 to 20 seconds. When stirred in cold water the powder gradual-
ly dispersed over a stirring period of the order of 8 seconds to produce a
reconstituted milk having its surface free of floating material. When stored
in a refrigerator at a temperature of 40F. for a period of 24 hours, no
appreciable separated cream was noted upon the surface of the liquid. Also
no appreciable amount of settled undissolved solids was noted. In general,
the product when reconstituted was of good quality, having a good mouth feel
and flavor.
106975Z
Example 2.
In this example a product was prepared having
a fat level of 28~, corresponding to whole milk powder.
The same cream mixture was prepared in the same manner as
described in Example 1. However, the source of anhydrous
powder comprised 25~ of commercial spray dried whole milk
powder having a fat level of 28~, blended with sufficient
spray dried nonfat milk powder to provide an average fat
level of 25%. The remainder of the process was the same as
in Example 1. The rate at which the blended powder was
supplied to the agglomerating chamber, and the rate of
feed of lecithin and homogenized ~ream mixture to the
chamber was such as to provide a final fat level of 2S~,
with a lecithin content of 0.8~. The final product was
read$1y dispersible i~ cold water with simple stirring
with a spoon. There was minimal cream separation upon
the surface of the reconstituted milk, and in general,
the reconstituted milk was of good ~uality with good flavor
- and mouth feel.
Taking the directions and data of Examples 1
and 2, one can readily determine how to apply the process
to the production of instant dry milk having fat levels
other than 5 or 28~. For fat content less than 5%,
such as 2~, the procedure would be substantially the same
as Example 1 and the source material would be nonfat dried
milk powder. For a fat level of say 15~, the source
material could be anhydrous whole milk powder blended
with nonf at powder to provide an average ~t level of
say 12%. Since the fat emulsion mix would have a fa' con-
tent to provide 15% in the final product, the amounts of
.
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.
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added emulsifier and nonfat milk solids added to the mix would be adjusted
accordingly.
In the foregoing references to the use of fat containing spray dried
milk, and particularly to whole milk, care should be taken to select a whole
milk of low heat type hauing its heat denaturable protein substantially unde-
natured and having a low solubility index ~e.g., 0.1 or less~. Also when
reconstituted with water, it should have good flavor characteristics and
should not be subject to objectionable fat separation. Such spray dried whole
milk is available commercially and is made by low heat processing before spray
drying. For special markets where a certain amount of cooked or heated fla-
vor is desired, medium heat powder may be used. While commercial spray dried
whole milk has been used with satisfactory results, it may be desirable to
produce such milk by special processing to avoid conceivable fat separation
in the reconstituted milk. Thus small amounts of emulsifier as previously
described would be added to the fluid milk, and the milk homogenized at high
pressures (e.g., 3000 to 3500 psig second stage) bef~re spray drying. The
amount of emulsifier used shoud be at a low level to avoid flavor impairment.
With such special processing the fat globules are reduced to small size (e.g. J
less than 3 microns) without release of free-fat or fat churning.
; 20 In the foregoing examples, crude lecithin is employed in liquid form.
When economically available we prefer to employ a purified form of lecithin
whieh may be in the form of a powder. The powder can be dispersed in a
suitable liquid medium, such as butter oil, and
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~069752
introduced with steam as indicated in ~igures 1 and 2. A particular com-
mercial purified lecithin is marketed by Lucas Meyer, Hamburg, West Germany,
under the trade name "Metarin". The use of such purified lecithin is des-
irable because it avoids possible flavor impairment of the final product,
such as may be caused by undesirable flavor components of crude lecithin.
*Trade Mark
