CA2084332A1

CA2084332A1 - Liquid milk-based product and a process for its production

Info

Publication number: CA2084332A1
Application number: CA002084332A
Authority: CA
Inventors: Michel John Arthur Groux; Willy Hugelshofer
Original assignee: Individual
Current assignee: Societe des Produits Nestle SA
Priority date: 1991-12-04
Filing date: 1992-12-02
Publication date: 1993-06-05
Also published as: EP0546200B2; AU2834092A; JPH05236873A; CN1074339A; AR248211A1; IE922844A1; DE69129461D1; BR9204641A; ZA928740B; EP0546200B1; NO924584D0; NO924584L; ATE166207T1; KR930011828A; ES2117633T3; DE69129461T2; DK0546200T3; DE69129461T3; MX9206907A; EP0546200A1

Abstract

A liquid milk-based product and a process for its produc-tion Abstract To prepare a mildly acidic, long-life beverage or cream based on milk, a sterile acidic agent is aseptically added to a neutral lactic base which has not been neutral-ized by addition of alkali and which has been sterilized without stabilizing salt and the mixture is aseptically packed in containers.

Description

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 2~8~3~2 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 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 208~?2 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.

2~8~3~2 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 2~ 32 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 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-208~3t,~2 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 2~332 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 2 0 ~

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~

Claims

1. A mildly acidic, sterilized liquid milk product, characterized in that it does not contain any added stabil-izing salt or alkali, has a pH value of 5.2 to 6.5 and shows no visible coagulation of proteins or phase separa-tion.

2. A product as claimed in claim 1, characterized in that it is in the form of a beverage based on milk and fruit juice.

3. A product as claimed in claim 1, characterized in that it is in the form of a coffee-flavoured milk.

4. A product as claimed in claim 3, characterized in that it also contains cocoa.

5. A product as claimed in claim 1, characterized in that it is in the form of an acidified cream.

6. A product as claimed in claim 1, characterized in that it is in the form of a dessert cream containing gelling and thickening carbohydrates and a fruit pulp.

7. A product as claimed in claim 2, characterized in that it also contains a carbonating agent.

8. A process for the production of a mildly acidic, sterilized liquid milk product, characterized in that a sterile acidic agent is aseptically added to a sterilized, neutral milk base which has not been neutralized by addi-tion of alkali and which is free from stabilizing salts.

9. A process as claimed in claim 8, characterized in that the acidic agent is a fruit juice or fruit pulp or an aqueous coffee extract optionally containing cocoa.

10. A process as claimed in claim 8 intended for the production of an acidified cream, characterized in that the acidic agent is an aqueous solution of a food-grade acid asepticized by microfiltration.