Note: Descriptions are shown in the official language in which they were submitted.
2~3 ~
This invention relates to a long-life liquid milk
product and to a process for its production.
At present, one o~ the following two methods may be
used for the production of a long-life liquid milk or
acidified cream:
the product is subjected to ultra-high-temperature
(UHT) sterilization and is then aseptically packed in
containers, for example of the "Tetra bricks~" type,
or
the non-sterilized product is packed in a container,
for example of the metal can type, and is sterilized
in its container.
In either case, stability to prolonged storage can
only be obtained if the pH is adjusted to a value of around
4.2 or lower and if a thickening agent, for example a
pectin, is added before sterilization.
One process for the production of long-life acidified
milk or cream, which is described in CA-PS 882,626, com-
prises a UHT sterilization step followed by rapid cooling,
acidification to a pH value close to the isoelectric pH of
casein (4.6 - 5.1) and gelling at ambient temperature.
In a very limited pH range, for example 6.3 or higher,
~5 it is possible to produce mildly acidic milk-based products
without gelling of the proteins, although in this case a
stabilizing salt, for example disodium hydrogen phosphate,
has to be added to protect the proteins against floccula-
tion during sterilization and during storage of the prod-
uct. Below a pH threshold of around 6.3, a neutralizing
agent in the form of an alkali, for example a strong base
such as sodium or potassium hydroxide, would have to be
added so that the product obtained would no longer be
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acidic. Unfortunately, the additives, such as stabilizing
salts, alter the taste of the product and adversely affec-t
its quality when added in effective quantities.
The present invention seeks to solve the problem of
producing mildly acidic milk products which have a pH of
or above approximately 5.2, can be sterilized without the
addition of stabilizing salts and show no visible coagul-
ation or phase separation in storage.
The product according to the invention is charac-
terized in that it does not contain any added stabilizingsalt or alkali, has a pH value of 5.2 to 6.5 and shows no
visible coagulation of proteins or phase separation.
In the context of the invention, a "mildly acidic
liquid milk product" is understood to be any product based
on milk proteins which has been heat~treated and acidified
by addition of an acidic agent.
The protein base may be milk or cream either in the
fresh state or reconstituted from powder. The acidic agent
may be an acid in solution, for example lactic acid or
citric acid, or an acidic beverage, for example a coffee
extract optionally containing cocoa, a fruit juice or fruit
pulp, for example natural pressed fruit juice.
Sweeteners, flavourings, carbonating agents, foaming
agents (for example in the case of a beverage) or even
thickening or gelling carbohydrates (in the case of a
dessert cream) may optional]y be added to the product.
The present invention also relates to a process for
the production of the milk product defined above, charac-
terized in that a sterile acidic agent is aseptically added
to a sterilized, neutral milk base free from stabilizing
salts.
To carry out the process, the milk or the cream
forming the milk base is treated by any means enabling it
to be sterilized by continuous UHT treatment. This may be
an indirect heating means, for example a plate or tube h~at
3 3 2
exchanger, or a direct heating means, for example a system
for directly injecting steam into the milk base. The
increase ln temperature is followed by a certain holding
time at the sterilization temperature, after which th~ milk
base is precooled, homogenized and then cooled.
Cooling may be carried out by means of a plate or tube
heat exchanger. Where steam is directly injected, a pre-
cooling step, for example by expansion in vacuo, is prefer-
ably inserted between the heat treatment and homogenization
steps.
An aqueous solution of an acidic agent, for example an
instant coffee extract, a fruit juice or a fruit pulp
suspension optionally acidified with a food-grade acid, for
example citric acid, is separately heat-treat~d or steril-
ized by microfiltration for the purpose of sterilization.
This operation may be carried out similarly to the heat
treatment of the lactic base.
In the variant relating to the production of an
acidified cream, the acidic agent may be a solution of a
food-grade acid cold-sterilized beforehand, for example by
microfiltration.
The acidic agent may also be a culture of lactic
bacteria which stop working at pH 5.2. This culture should
be prepared under aseptic conditions, for example steril-
ized by microfiltration and added to the protein base after
its heat treatment.
All the operations following the thermal sterilizing
treatments should of course be carried out under aseptic
conditions.
After asepticization, cooling and, optionally, homo-
genization, the milk base and the acidic agent are mixed
either in batches, for example in a sterilised tank equiped with a stirrer~
or continously in a tube connected to an aseptic filling station.
Finally, the products are packed in containers, for example
in multilayer cartons of the "Tetra bricks~" type or in
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cans .
In cases where it is desired to produce a carbonated
beverage, for example a carbonated milk flavoured with
fruit juices, C02 prefiltered under sterile conditions is
injected into the mixture of milk base and acidic agent.
In cases where it is desired to produce a foaming
beverage, a foaming agent may be added and a space may be
left free in the container for generation of the foam, for
example by shaking just before consumption.
The process according to the inv~ntion provides access
to hitherto unknown products, for example ready to-drink
liquid beverages of the cappuccino type, which it had not
been known how to produce even using the conventional
method with stabilizing salt.
The invention i5 illustrated by the following Examples
in which parts and percentages are by weight unless other-
wise indicated.
Example ~ - Co~fee-flavoured milk
1.1 InvPntion
3.4 kg instant coffee powder and 10.4 kg sucrose - dry
mixed beforehand - are added to 70 kg water. Water is then
added to make up 99.2 kg.
Separately, 100.84 kg milk containing 3% milk fats are
~5 weighed, pasteurized at 85C and then cooled to below 10C.
After continuous preheating to 80C, the milk is brought to
150C by direct injection of steam, kept at that tempera-
ture for 3 s and then cooled by expansion in vacuo to 78C.
The milk is then homogenized in two steps at 250 and then
50 b and cooled to 20C. The milk thus asepticized is then
stored in a sterilized tank equiped with a stirrer.
Still separately, the aqueous solution of sweetened
coffee is heat treated for 5 s at 145C in a plate heat
exchanger and is then continuously cooled to 20C - still
in the plate heat exchanger. This asepticiæed solution is
2 ~
gradually added with slow stirring to the ~septicized milk
in the sterile tank.
The mixture is then aseptically packed in 200 ml Tetra
Pack~ multilayer cartons.
The beverage obtained has a pH value of 6.17.
1.2 Comparison
For comparison, an aqueous solution of sweetened
instant coffee is prepared by addition to 70 kg water of
0.28 kg NazHPO4 o 2H20, 3.4 ky instant coffee and 10.4 kg
sucrose, the last three ingredients having been dry mixed
beforehand.
Separately, 100.84 kg milk containing 3% milk fats are
pasteurized for 5 s at 85C, homogenized at 100 b/85C,
cooled to below 10C and added to the above solution of
sugar, coffee extract and stabilizing salt.
The mixture is then made up with water to 200 kg,
sterilized for 3 s at 150C after continuous prehPating to
80C, cooled by expansion in vacuo to 78C, homogenized at
2S0 + 50 b, cooled to 20C and aseptically pacXed in 200 ml
Tetra Pack~ multilayer cartons.
The mixture obtained has a pH value of 6.43.
Evaluatio~ of the products
Unexpectedly, the product prepared in accordance with
l.l has a perfectly homogeneous structure despite the
absence of stabilizing salt (Na2HPO4 2H2O). After two
months at 20C and at 30C, the two products are still
perfectly homogeneous. In addition, the product prepared
in accordance with 1.1, on tasting, has a stronger and more
distinct taste of coffee than that prepared in accordance
with 1.2.
Example 2 - Coffee-flavoured milk
The procedure is exactly the same as in Example 1.1
3 ~' ~
except that, on this occasion, the aqueous solution is not
treated for 5 s at 145C using an in~irect heating system,
but instead for 3 s at 150C by direct in~ection of steam.
On evaluation, the product is found to be perfectly
homogeneous despite the absence of stabilizing salt (Na2
HPO4 2H2O) and also to have a more distinct but less
strong taste of coffee than the comparison product 1.~ for
the same pH as the product of Example 1.1
Example 3 - Cappucoino
3.1 Invention
7 kg sucrose and 2 kg instant coffee powder - dry
mixed beforehand - are added to 70 kg water. Water is then
added to make up 89.89 kg.
Separately, 100 kg milk containing 3% milk fats are
weighed, pasteurized, homogenized and cooled as in Example
1 . 1 .
2 kg partly defatted cocoa powder, 40 g of an anti-
sedimenting agent for the cocoa (Genulacta K-100~), 70 g
cooking salt and 8 kg sucrose - all these ingredients
having been dry mixed beforehand - are added to the cooled
milk.
This mixture is then sterilized for 3 s at 150C by
direct injection of steam, homogenized and cooled in the
same way as the mixture of Example 1.1
This asepticized milk is stored in a sterilized tank
equipped with a stirrer.
Still separately, the aqueous solution of sugar and
coffee is heat treated as in Example 1.1 and this asep-
ticized solution i5 gradually added with slow stirring tothe cocoa-flavoured milk stored in the sterilized tank.
The mixture is then packed under aseptic conditions. The
product obtained has a pH value of 6.49.
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3.2 Comparison
For unexplained reasons, it was not possible to
produce a milk product containing both coffee and coc~a by
a process similar to that of Comparison Exampl~ 1.2 The
product obtained was either inhomogeneous or rapidly became
inhomogeneous after storage in its container for a few
days.
E~aluation of the product a~cording to the inve~tio~ i3.1~
This product is perfectly homogeneous and remains
homogeneous in storage. At the very most, the cocoa
sediments slightly with time, but no more so than any
commercially available cocoa-flavoured milk drink packed
under aseptic conditions.
Example 4 - cappuo~ino
The procedure is the same as in Example 3.1 except for
the following difference:
Instead of adding the asepticized aqueous solution of
sugar and coffee to the sterilized tank containing the
similarly asepticized cocoa-flavoured milk and mixing the
two phases before packing the whole in containers, the
asepticized aqueous solution of sugar and coffee is contin-
uously mixed with the asepticized cocoa-flavoured milk, for
example by coupling two pipes to fonm a T so ~ t the mlxture
is immediately homogeneous. The mixture is aseptically
packed without waiting.
Example 5 - Acidified ~ream
200 kg of a milk cream containing 30% fats are pre-
pared, pasteurized for 5 s at 85C, homogenized at 50 b at
that temperature and then cooled to below 10C.
The cream is then sterilized for 3 s at 150C after
preheating to 80C in a plate heat exchanger, cooled by
expansion in vacuo at 78C, homogenized at 50 b at that
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temperature and therl cooled to 20C.
A 10% aqueous lactic acid solution subjected be~ore-
hand to sterile filtration through 0.2 micron microfilters
is injected into the pipe leading from the cooler to the
packaging machine. This solution has a pH o~ 1.9. 1.2 and
3%, resp~ctively, of this filtered solution are added and
the mixture is aseptically packed in 200 ml Tetra Pack~
cartons.
10 Evaluatio~ of the products
% of 10% lacti¢ aaid ~olution a~aad
1 2 3
Appearance Homogeneous Homogeneous Ho~ogeneous,
fluid fluid very slight-
ly thickened
pH 6 5.98 5.5
Taste Hardly any, Very Sliyhtly
very slight- slightly acidic
ly acidic acidic
Unexpectedly, the product containing 3~ of a 10%
lactic acid solution may readily be used in cooking for the
preparation of hot sauces based on white wine without the
cream showing any sign of coagulating in the process.
Note
In the case of acidified cream, it is not possible to
apply a conventional method (in one step) as for the
coffee-flavoured milk of Example 1.1.
In other words, unless the acidity is neutralized
before the UHT treatment, which would destroy the present
objective, it is not possible to sterilize an acidic
product, even one enriched with gelling agents/stabilizers,
without the product showing obvious signs of coagulation
unless it is acidified (biologically or chemically) to a pH
value of 4.2 to 4.3. In the latter case, the product in-
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evitably has an acidic taste and yenerally has to bestabilized, for example against heat, by addition of
pectin.
~xa~ple 6 - Milk flavoured with fruit juices
200 kg milk containing 3% lactic fats are prepared.
This milk is pasteurized, homogenized, cooled, sterilized,
homogenized and finally cooled in the same way as in
Example 1.1.
Separately but simultaneously, a ~ruit juice (oranges,
red grapes) is sterilized in the same way and under the
same conditions as for the aqueous coffee/sugar solution of
Example 1.1.
The two separate lines are designed so that their
respective flows can be adjusted, for example to 100 parts
milk and 10 parts fruit juice or any other desirable
combination.
In this way, mixtures can be aseptically packed in
asepticized cans respectively containing 10, 20, 30, 40,
50 and 60 parts orange ~uice to 100 parts milk.
Evaluation of thc products
All the mixtures containing up to 100 parts milk and
40 parts orange juice are homogeneous and remain homogene-
ous during storage. These mixtures have a pH of or above5.3 (as measured at 20C), namely 6.2, 5.89, 5.51 and 5.3,
respectively.
By contrast, the mixtures containing more than 50
parts orange juice to 100 parts milk show phase separation
(formation of whey after only 24 h. These products all
have a pH below 5.3, for example 4.84 for the product
containing 60 parts orange juice.
The same process was repeated with red grape juice
(appreciably more acidic than orange juice) and the obser-
vations are virtually the same. All the mixtures having a
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pH above 5.2 are homogeneous and remain homogeneous while
those having a pH below 5.2 rapidly undergo phase separa-
tion.
Example 7 - Milk flavoured with ~ruit juices, carbonated
One of the mixtures of Example 6 is prepared and
asepticized in the same way. This mixture is stored in a
sterilized tank. The mixture in question consists of 100
parts milk and 30 parts fruit juice.
Separately, COz ob~ained from a pressurized source is
filtered under sterile conditions and injected into the
pipe leading from the sterilized tank to the aseptic can
filling station. An aseptic mixing pump or incorporated
static mixing elements is/are inserted into the pipe just
after the injection of CO2.
A very refreshing carbonated milk drink flavoured with
orange juice is obtained in this way.
Example 8 - De~ert ~ream
The Example carried out with an acidic pulp of coco-
nuts is not exhaustive. Any acidic fruit would be equally
suitable.
A concentrated milk obtained by partial evaporation of
the water of a whole milk sterilized beforehand for 4 s at
145C by direct injection of steam is initially prepared.
Separately, an aqueous suspension of various modified
and unmodified starches, thickeners and sucrose - all these
ingredients having been dry mixed beforehand - is prepared
in a cooker. This suspension is added to the concentrated
milk.
After preheating to 80C, the mixture is sterilized
~or 15 s at 148C, cooled by expansion in vacuo to 80C and
finally cooled to 20Co The product is stored in a steril-
ized tank.
Separately, a flavoured coconut purée stabilized with
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11
thickeners and citric acid (pH 4.1) is sterilized for 10 s
at 145C and cooled to 60C in a tube heat exchanger.
The asepticized purée is continuously introduced in a
quantity of 6~ into the pipe leading from the sterilized
S tank to a can filling station.
This cream is and remains perfectly homogeneous. It
has a pH value of 6.4~
