IE922844A1 - A liquid milk-based product and a process for its production - Google Patents

Abstract

In order to manufacture a weakly acidic long preservation beverage or cream containing a lactic base, a sterile acidic agent is aseptically added to a neutral lactic base which has not been neutralised by addition of alkali and which has been sterilised without stabilising salt and the mixture is aseptically packaged in packages.

Description

This invention relates to a long-life liquid milk product and to a process for its production.

At present, one of 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, comprises 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, it is possible to produce mildly acidic milk-baced 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 flocculation during sterilization and during storage of the product. 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 OPEN TO PUBLIC INSPECTION E 922844 acidic. Unfortunately, the additives, such as stabilizing salts, alter the taste of the product and adversely affect its quality when added in effective quantities.

The present invention seeks to solve the problem of 5 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 coagulation or phase separation in storage.

The product according to the invention is charac10 terized in that it does not contain any added stabilizing salt 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 optionally be added to the product.

The present invention also relates to a process for the production of the milk product defined above, characterized 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 heat exchanger, or a direct heating means, for example a system for directly injecting steam into the milk base. The increase in temperature is followed by a certain holding time at the sterilization temperature, after which the 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 precooling step, for example by expansion in vacuo, is preferably 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-treated or steril15 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 steril25 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, homogenization, 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 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 invention 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 is illustrated by the following Examples in which parts and percentages are by weight unless otherwise indicated.

Example 1 - Coffee-flavoured milk 1.1 Invention 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 25 weighed, pasteurized at 85°C and then cooled to below 10°C. After continuous preheating to 80 °C, the milk is brought to 150 °C by direct injection of steam, kept at that temperature for 3 s and then cooled by expansion in vacuo to 78 °C. The milk is then homogenized in two steps at 250 and then 50 b and cooled to 20°C. 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 145°C in a plate heat exchanger and is then continuously cooled to 20°C - still in the plate heat exchanger. This asepticized solution is gradually added with slow stirring to the asepticized 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 Na2HPO4 · 2HZO, 3.4 kg 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 85°C, homogenized at 100 b/85°C, cooled to below 10°C 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 150 °C after continuous preheating to 80°C, cooled by expansion in vacuo to 78°C, homogenized at 250 + 50 b, cooled to 20°C and aseptically packed in 200 ml Tetra Pack® multilayer cartons.

The mixture obtained has a pH value of 6.43.

Evaluation of the products Unexpectedly, the product prepared in accordance with 1.1 has a perfectly homogeneous structure despite the absence of stabilizing salt (Na2HPO4 · 2H2O) . After two months at 20°C and at 30°C, 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 except that, on this occasion, the aqueous solution is not treated for 5 s at 145°C using an indirect heating system, but instead for 3 s at 150°C by direct injection of steam.

On evaluation, the product is found to be perfectly 5 homogeneous despite the absence of stabilizing salt (Na2 ΗΡΟ4 · 2Hz0) and also to have a more distinct but less strong taste of coffee than the comparison product 1.2 for the same pH as the product of Example 1.1 Example 3 - Cappuccino 3.1 Invention 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. kg partly defatted cocoa powder, 40 g of an antisedimenting agent for the cocoa (Genulacta K-lOO·), 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 150°C 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 asep30 ticized solution is gradually added with slow stirring to the 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. 3.2 Comparison For unexplained reasons, it was not possible to produce a milk product containing both coffee and cocoa by a process similar to that of Comparison Example 1.2 The product obtained was either inhomogeneous or rapidly became inhomogeneous after storage in its container for a few days.

Evaluation of the product according to the invention (3.1) 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 - Cappuccino The procedure is the same as in Example 3. l 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 continuously mixed with the asepticized cocoa-flavoured milk, for example by coupling two pipes to form a T so that the mixture is immediately homogeneous. The mixture is aseptically packed without waiting.

Example 5 - Acidified cream 200 kg of a milk cream containing 30% fats are prepared, pasteurized for 5 s at 85°C, homogenized at 50 b at that temperature and then cooled to below 10°C.

The cream is then sterilized for 3 s at 150°C after preheating to 80°C in a plate heat exchanger, cooled by expansion in vacuo at 78’C, homogenized at 50 b at that temperature and then cooled to 20’C.

A 10% aqueous lactic acid solution subjected beforehand 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 of 1.9. 1.2 and 3%, respectively, of this filtered solution are added and the mixture is aseptically packed in 200 ml Tetra Pack® cartons.

Evaluation of the products % of 10% lactic acid solution added 3 Appearance pH Taste Homogeneous fluid Hardly any, very slight ly acidic Homogeneous fluid .98 Very slightly acidic Homogeneous, very slightly thickened .5 Slightly 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 inIE 922844 evitably has an acidic taste and generally has to be stabilized, for example against heat, by addition of pectin.

Example 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 l.l.

Separately but simultaneously, a fruit 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 juice to 100 parts milk.

Evaluation of the products All the mixtures containing up to 100 parts milk and 40 parts orange juice are homogeneous and remain homogene25 ous during storage. These mixtures have a pH of or above .3 (as measured at 20°C), 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 obser35 vations are virtually the same. All the mixtures having a pH above 5.2 are homogeneous and remain homogeneous while those having a pH below 5.2 rapidly undergo phase separation.

Example 7 - Milk flavoured with fruit 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, CO2 obtained 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 - Dessert cream The Example carried out with an acidic pulp of coconuts 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 145°C 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 80°C, the mixture is sterilized for 15 s at 148°C, cooled by expansion in vacuo to 80’C and finally cooled to 20'C. The product is stored in a sterilized tank.

Separately, a flavoured coconut puree stabilized with thickeners and citric acid (pH 4.1) is sterilized for 10 s at 145 °C and cooled to 60°C in a tube heat exchanger.

The asepticized puree is continuously introduced in a quantity of 6% into the pipe leading from the sterilized tank to a can filling station.

This cream is and remains perfectly homogeneous. It has a pH value of 6.4.

Claims (9)

1. A mildly acidic, sterilized liquid milk product, characterized in that it does not contain any added stabilizing salt or alkali, has a pH value of 5.2 to 6.5 and 5 shows no visible coagulation of proteins or phase separation.

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. 10 3. it A product as is in the form claimed in claim 1, characterized of a coffee-flavoured milk. in that 4. it A product as also contains claimed in claim cocoa. 3, characterized in that 15 5. it A product as is in the form claimed in claim of an acidified 1, characterized cream. in that 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.

3. 7. A product as claimed in claim 2, characterized in that 20 it also contains a carbonating agent.

4. 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 addi25 tion of alkali and which is free from stabilizing salts.

5. 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.

6. 10. A process as claimed in claim 8 intended for the 30 production of an acidified cream, characterized in that the acidic agent is an aqueous solution of a food-grade acid asepticized by microfiltration.

7. 11. A process for the production of a mildlv acidic, sterilized liquid milk product, substantially as hereinbefore described with reference to any of Examples 1 to 8.

8. 12. A mildly acidic,sterilized liquid milk product, whenever Dreoared by a process as claimed in any of claims 8 to 11.

9. 13. A mildly acidic, sterilized liquid milk product, substantially as hereinbefore described with reference to any of Examples 1 to 8.