IE52676B1 - Process for the production of a fermented milk - Google Patents

Abstract

1. Claims for the contracting States : BE, CH, DE, GB, IT, LI, LU, NL, SE Process for the production of a fermented milk substantially free from live germs, having a long preservation time, characterized by aseptically introducing lactic fermentation germs into sterilized water, adding under sterile conditions the water containing said germs to UHT-sterilized milk, aseptically packing the resulting mixture in sterile containers, and allowing the lactic fermentation to develop to completion within said containers, thereby obtaining a fermented milk substantially free from live germs. 1. Claims for the contracting State : AT Process for the production of a fermented milk substantially free from live germs, having a long preservation time, characterized by aseptically introducing lactic fermentation germs into sterilized water, adding under sterile conditions the water containing said germs to UHT-sterilized milk, aseptically packing the resulting mixture in sterile containers, and allowing the lactic fermentation to develop to completion within said containers, thereby obtaining a fermented milk substantially free from live germs.

Description

This invention relates to a fermented milk and to a process for its production..

Fermented milks have been known for a very long time, particularly in Arab countries and in Brittany (under the name of Ribot milk! lait Ribot).

At the present time, fermented milks are produced in the following manners the raw milk is first skimmed, and is then pasteurized to remove the deleterious germs and destroy the common flora. After cooling to 20°C, it is seeded with selected lactic ferments, generally as mixtures of two or more types of germs. The milk is allowed to stand at a temperature of 18-20°C for a period of time of about 12 hours, in order to obtain a coagulum characteristic of fermented milk, after which it is cooled to 10°C and is submitted to a mild stirring process before packing.

This product exhibits a slightly acidic, fresh taste which is appreciated by consumers, has a liquid consistency after stirring, and has a white colour. In this product, the ferments are live.

This product may be stored at a temperature of about 5°C for a period of time of about 3 weeks.

Its preservation time is thus very limited and requires cold storage.

An article by J. Rasic (Yoghurt", 1978, Techn. Dairy Publ. House, p. 285) describes an analogous technique which uses aseptic conditions. However, in this technique as in the conventional technique, the fermentation is interrupted by lowering the temperature, thus obtaining a product containing living germs.

It is an object of the present invention to provide a fermented milk which exhibits a markedly more extended preservation time and which, in addition, may be stored at ambient temperature.

Therefore, the present invention provides a process for the production of a fermented milk substantially free from live germs, having a long preservation time, comprising aseptlcally introducing lactic fermentation germs into sterilized water, adding the germ-containing water to UHT sterilized milk, under sterile conditions, aseptically packing the resulting mixture in sterile containers, and then allowing the lactic fermentation to develop to completion within such containers, thus producing a fermented milk substantiallvfree from live germs.

The process of this invention differs from the prior art with respect to: a) the nature of the seeded milk, b) the seeding conditions, c) the packing conditions, and d) the fermentation conditions, and results in a product which, while exhibiting a taste similar to that of conventional fermented milk, differs markedly from conventional fermented milk.

Thus, firstly, the nature of the seeded milk is different. Instead of using pasteurized milk, use is made of UHT (Ultra High Temperature) sterilized milk, i.e., milk that has undergone a continuous high-temperature thermal sterilization treatment for a short period of time.

This conventional sterilization treatment is generally conducted at a temperature of about 140°C for a period of time of 2 seconds.

It is advantageously preceded by a pasteurization designed to remove most of the germs, and provides a germ-free milk.

On the other hand, the seeding conditions are different. While the prior art did not call for any particular precautions from the standpoint of asepsis,in the method according to the present invention it is reguired that the seeding process be effected aseptically.

Therefore, the lactic fermentation germs are added to sterilized water under aseptic conditions, so as to avoid the introduction of any other germ.

Sterilization of the water may be effected under the action of an ultraviolet radiation.

A predetermined amount of water containing the lactic fermentation germs is added to the UHT sterilized milk, under sterile conditions. This is readily effected by injecting the water containing the lactic fermentation germs into the line used to supply the UHT milk from the UHT unit to the packing unit.

The packing conditions are also different, because, instead of effecting the packing after fermentation and without any particular precautions from the standpoint of asepsis, in the process of this invention the packing is effected aseptically in sterile containers, and, this, prior to the fermentation.

For this purpose, use may be made of the aseptic packing units used for packing UHT milk, such as the Tetra Pak system.

This system uses a cardboard container which is formed by the packing machine after immersion in hydrogen peroxide and drying in hot air. The containers are filled in a sterile enclosure, after which the containers are sealed.

The fermentation conditions are also different because, instead of effecting a fermentation for about 12 hours at a temperature of 18-2O°C and then interrupting the fermentation by cooling, in the process of this invention the lactic fermentation is allowed to develop and to go to completion. This may be effected by maintaining the containers at a temperature of at least 18°C for one week.

Beyond this period of time, the lactic fermentation ceases because, on the one hand, the lactose of the milk is partly used and, on the other hand, the bacteria are destroyed by autolysis.

This is readily explained by reference to accompanying Fig.l which shows growth curve (A) and acidification curve (B).

The growth curve shows a short latency period (up to point a), followed by a development stage (up to point b), a stationary stage (between b and c), and a declining stage. Concomitantly, acidity increases and when is attains a value between points d and e the milk is converted to a gel, which corresponds to the formation of the coagulum.

Beyond a certain period of time, the lactic bacteria are destroyed, and there is obtained a fermented milk of slightly acidic taste and substantially free from germs, because these have been removed by autolysis.

Such a product is stable and does not undergo any physicochemical degradation.

It is solely the defective sealing of the package that is liable to limit the preservation of this fermented milk.

Practically, it is possible to keep such a fermented milk for a period of time of at least 4 months at room temperature, which constitutes a most substantial advantage with respect to conventional fermented milk.

Examples of lactic fermentation germs useful in the process of this invention include the following: - Streptococcus cremoris - Strepcocoecus lactis - Streptococcus diacetilactls - Streptococcus thermophllus - Lactobacillus bulgaricus . - Lactobacillus acidophilus - Lactobacillus bifidus - Leuconostoc citrovorum Such germs are advantageously used in the form of frozen granules . They may be added to sterilized water at a rate of about 1 g/litre sterilized water, which provides 5 7 a population of 5x10 to 5x10 germs per ml.

The water containing such germs is added to the UHT sterilized milk, advantageously in an amount of at least 5 ml/litre of milk.

Accompanying Fig.2 illustrates a flow diagram for the process of this invention.

The processing unit includes a tank 1 sealed with a tilt-up lid 2 to which is attached a UV lamp 3 provided within tank 1 when lid 2 is closed. Said tank 1 is connected to a line 4 for the supply of water and to an outgoing line 5. Line 5 is provided with a peristaltic pump 6 which sends the water from tank 1 to a three-way valve 7 connected, on the one hand to an injection line 8 and, on the other hand, to a pipe 9 for back-feeding to tank 1, which is provided with a flow-rate control valve 10.

Injection line 8 is connected with outgoing pipe 11 for the UHT sterilized milk of a UHT sterilization unit 12 for the milk entering at 13.

Line 11 is connected with a sterile packing unit 14 of Tetra Pak type in which the cardboard used to make the container enters at 15 and the package containing the seeded milk exits at 16 after sealing.

The following operating procedure is used: water is introduced into tank 1 by line 4 and this water is sterilized by means of UV lamp 3. Lid 2 is then opened, and the lactic fermentation germs are introduced as frozen granules while maintaining throughout this operation an upflowing stream of hot air above the opening to prevait the introduction of other germs. This provides a substantial stock of lactic ferments diluted in sterile water.

By means of peristaltic pump 6, water is sent from tank 1 to line 8, the back-feed rate to tank 1 being controlled by valve 10.

The water of tank 1 is thus injected at the required dosage in outgoing line 11 of the UHT sterilized 53676 milk from sterilization unit 12. The seeded milk is then aseptically packed in packing unit 15.

The packages filled with seeded milk which have been sealed in processing unit 15 are stored at a tem perature of about 20’C for one week, prior to being shipped out.

Claims (10)

1. A process for the production of a fermented milk substantially free from live germs, having a long preservation time, comprising aseptically introducing

2. A process as claimed inclaim 1, wherein the sterilization of the water is effected under the action of an ultraviolet radiation. lb

3. A process as claimed in claim 1 or 2, wherein the addition of the germ-containing water to the UHT sterilized milk is effected by injection of said water into the pipe leading the UHT sterilized milk from an UHT sterilization unit to an aseptic packing unit. 20

4. A process as claimed in any one of claims 1-3, wherein the fermentation is allowed to develop and to come to completion by storing the containers containing the seeded milk at a temperature of at least 18°C for a period of time of at least one week. 25 5. A process as claimed in any one of claims 1-4, wherein the germs are introduced into the sterilized water as frozen granules.

5. As illustrated in the accompanying drawings. 5 lactic fermentation germs into sterilized water, adding under sterile conditions the water containing said germs to UHT (as hereinbefore defined) sterilized milk, aseptically packing the resulting mixture in sterile containers, and allowing the lactic fermentation to develop to completion within said containers, 10 thereby obtaining a fermented milk substantially free from live germs.

6. A process as claimed in any one of claims 1-5, wherein the germs are added to the sterilized water in 30 an amount of about 1 g/litre.

7. A process as claimed in claim 6, wherein the germcontaining water is added to the UHT sterilized milk in an amount of at least 5 ml/litre of milk.

8. Milk having undergone a lactic fermentation, 35 packed in sealed containers and substantially free from live germs. - 10

9. A process according to claim 1 for the production of a fermented milk substantially free from live germs, having a long preservation time, substantially as hereinbefore described with particular reference to and

10. Fermented milk whenever produced by a process claimed in a preceding claim.