MXPA97009517A - Procedure of fermentation in conti - Google Patents

Abstract

Procedure for continuous preparation of a fermented milk in which: (1) is prepared in a first device, a milk fermented by lactic acid bacteria, that fermented milk is subjected to mixing conditions and pH such that the syneresis of milk is not produce, and that pH is regulated by continuous addition of unfermented milk in the first device and continuous intake of fermented milk from the first device; (2) in a second post-acidification device, the fermented milk taken from the first device is cooled, at a temperature below 15 ° C such that the fermented milk is subjected to a post-addition, the residence time of the milk fermented in the second device is adjusted so that, at the outlet of the milk, the pH of the milk fermented, is lower than 4.7; (3) a continuous of the second device is taken, a fermented milk that has a pH lower than 4

Description

CONTINUOUS FERMENTATION PROCEDURE DESCRIPTION The present invention has for its object a continuous process for preparing a milk fermented by a lactic acid bacterium.

It is the technique: The continuous fermentation of a milk by lactic acid bacteria, needs a mixing of the milk so that it can, in the fermentation vat, add non-fermented milk and take fermented milk. When the pH of a milk of this mixed type reaches a value of 4.8-5.2, the milk casein mycelia tend to agglomerate and concentrate until they coagulate irreversibly. This phenomenon of coagulation, called "syneresis" unfortunately destroys the consistency of fermented milk (Veisseyre, Technologie du Lair, Ed. La Maison Rustique, Paris, 1975, I.S.B.N. 2-7066-0018-7, pages 427-438). To reduce this drawback, it is conceivable to prepare a fermented milk in a semi-continuous manner, continuously preparing a pre-culture of lactic bacteria having a pH higher than 5 in such a way as to avoid the appearance of a complete syneresis. , and then in second place inoculating a milk with this pre-culture and fermenting it by a bath without mixing until a pH of approximately 4.5, for example. The continuous preparation of a pre-culture of lactic bacteria, as well as the use of this pre-0 crop in the framework of the semi-continuous manufacture of a fermented milk, is well known. By way of example, the procedures described by Driessen et al (Biotechnology and Bioengineering, 29, 821-839, 1977) may be cited; Lelieved et al (Bioengineering, 11, 39- «5 40, 1976); Lelieved (Process Biochemistry, 19, 112-113, 1984); MacBean et al (Biochemestry and Bioengineering, 21, 1517-1531, 1979); Prevost et al (Milchwissenschaft, 43, 622,719, 1988); Reichart (Acta Alimentaria, 8, 373-381, 1979); Schuler (DE-2006894); and Spreer et al. (Lebensmi ttel -biotechnologie, 7, 28-31, 1991), for example. In the course of a continuous process for preparing a fermented milk, it is also possible to partially prevent the complete formation of a syneresis.

For this purpose, US-3924007 describes a continuous process in which, first, a pre-culture of lactic bacteria having a pH greater than 5 is prepared in a continuous manner in order to avoid the syneresis of the milk, then the second is continuously fermented. This pre-culture mixing it in such a way that a mixing gradient is installed in the fermented milk which avoids the appearance of a complete syneresis of the milk. A gradient of this type of mixing was also used by Van der Loo in the context of the continuous preparation of a fermented milk (Deutsche Milchwirt-schaft, 29, 1199-1202, 1980). In this process, a milk fermentation tank, a pre-culture of lactic acid bacteria at a pH of 5.7 is added, the fermented milk in a tank is subjected to a mixing gradient, and fermented milk is added to the milk. from below the Cuba. Unfortunately, those continuous procedures for preparing a fermented milk are not entirely satisfactory. In effect, the milks that come from a continuous fermentation never have a pH lower than 4.7, under penalty of reinforcing the syneresis of the milk. In certain cases, these fermented milks are also subjected to shearing forces such that the consistency of the milk is profoundly modified.

The object of the present invention is to reduce the drawbacks of the prior art by providing a method that can be easily implemented.

SUMMARY OF THE INVENTION: For this purpose, the invention relates to a method for continuously preparing a fermented milk in which: a milk fermented by lactic acid bacteria is prepared in a first device; that fermented milk is subjected to mixing and pH conditions such that the syneresis of the milk does not occur, and that pH is regulated by continuous addition of unfermented milk in the first device and continuous intake of fermented milk from the first device; - in a second device, the fermented milk taken from the first device is cooled to a temperature below 15 ° C in such a way that the fermented milk is subjected to a post-acidification; the residence time of the fermented milk in the second device is adjusted so that, at the outlet thereof, the pH of the fermented milk is less than 4.7; - a fermented milk having a pH lower than 4.7 is taken continuously from the second device.

DETAILED DESCRIPTION OF THE INVENTION: For milk, it is meant to designate, on the one hand, a milk of animal origin, such as cow's milk, goat's milk, sheep's milk, buffalo's milk, zebu's milk, mare's milk, donkey's milk, c camel, etc ... That milk can be a milk to the native state, a reconstituted milk, a skimmed milk, or a milk added of necessary compounds to the growth of the bacteria or to the subsequent treatment of the fermented milk, as fats, extract of yeast, peptone and / or a surfactant, for example. The term milk is also applied to what is commonly called a vegetable milk, ie an extract of vegetable materials treated or not, such as legumes (soybeans, chickpeas, lentils, etc.) or oilseeds (rapeseed, soybeans, Sesame (sesame), cotton, etc ...), extract containing proteins in solution or colloidal suspension, coagulable by chemical action, by acid fermentation and / or by heat. These or vegetable milks may have undergone heat treatments analogous to those of animal milks. They may also have undergone treatments that are their own, such as discoloration, and treatments to suppress undesirable tastes. Finally, the word milk also designates mixtures of animal milks and vegetable milks. That milk must be pasteurized, that is, subjected to a heat treatment and / or high pressure that inactivates all living germs. These techniques are well known by the man of the trade. That milk can be fermented by at least one strain of lactic bacteria, especially by bifidobacteria such as Bifidobacterium inf antis, lactococci such as Lactococcus lactis subspecies lactis, Lactococcus lactis subspecies crémor is, Lactococcus lactis subspecies lactic biovar diacetylactis, streptococci such such as Streptococcus thermophilus, Streptococcus, faecal is, lactobacilli such as Lactobacillus delbruecki subsp. bulgaricus, Lactobacillus acidophilus, Lactobacillus johnsonii, Lactobacillus amylovorus, Lactobacillus hel veticus, Lactobacillus farciminis, Lactobacillus alimentarius, Lactobacillus casei subspecies casei, Lactobacillus delbruckii subspecies lactis, Lactobacillus sake, Lactobacillus curve your, pediococci such as Pediococcus pentosaceus, Pediococcus acidilactici, Pediococcus halophil us, Staphylococci such as Staphylococcus xylosas, Staphylococcus carnosus, Micrococci such as Micrococcus varians, for example.

The invention is particularly indicated for microorganisms that are sensitive to culture conditions, especially sensitive to the presence of air, for example. Particularly sensitive microorganisms may include probiotic lactic acid bacteria, such as the strain Lactobacillus acidophilus CNCM 1-1225, which is described in EP-577904 (reclassified L. johnsonii), ie the lactic acid bacteria which can adhere to the human intestinal cells, exclude pathogenic bacteria on human intestinal cells, and increase the property of the human body to defend against pathogens, for example by increasing the phagocytosis capacities of granulocytes that come from human blood (J. of Diary Science, 78, 491 -197, 1995: capacity of immunomodulation of the strain La-1 that was deposited in the Pasteur Institute under the number CNCM 1-1225). By the word "continuous", it means the production that is carried out continuously, of a fermented milk; the different flows of materials involved in the process according to the invention can be controlled by means of valves that also function as pumps; those valves are attached to probes and calculators that regulate the opening of the valves; the opening of the valves can also be temporarily closed. To implement the present invention, in a first step, a first milk fermented with lactic acid bacteria is prepared continuously, at a temperature adapted to the growth of the selected bacterial species; that fermented milk is subjected to mixing and pH conditions, such that the syneresis of the milk does not take place, and the pH is regulated at a defined level by continuous addition of pasteurized milk and continuous intake of fermented milk. These operations can be carried out in any device adapted to the mixed culture of lactic acid bacteria, but in particular in a heated tank having a system that mixes the fermented medium and that has an inlet for the pasteurized (unfermented) milk and an outlet for the milk fermented the pH is regulated by continuous addition of pasteurized milk and constant intake of fermented milk by means of probes that analyze the pH and volume, and valves at the entrance and exit of the tank; the opening of the valves can be controlled by a calculator attached to the probes, for example. It is of the competence of the man of the trade, to put in its point that type of device. This device can be very well adapted to those described by Driessen et al (Biotechnology and Bioengineering, 29, 821,839, 1977) by Lelieved et al (Bioengineering, 11, 39-40, 1976), by Lilieved (Process Biochemestry, 19, 112- 113, 1984), by MacBean et al (Biotechnology and Bioengineering, 21, 1517-1531, 1979), by Prevost et al (Milchwissenechaft, 43, 622-719, 1988), by Reichart (Acta Alimentaria, 8, 373-381 , 1979), by Schuler (DE-2006894), and by Speer et al (Lebensmi ttel -biotechnologie, 7, 28-31, 1991), for example. In particular, if a milk is fermented by probiotic lactic bacteria, it can be envisaged to continuously ferment that milk under a neutral gas atmosphere, such as carbon dioxide or nitrogen, for example. Preferably, the fermented milk taken continuously from the first device comprises at least 196 cfu / g of lactic acid bacteria (cfu comes from the English expression Colony forming Unit), especially 107 -109 cfu / g. This fermented milk can also present a principle of formation of a syneresis that should be, preferably, barely perceptible in the mouth of a taster. When the pH of the fermented milk is of the order of 5.2, the casein micelles are sufficiently unstable to begin to agglutinate. Between the pH of 4.9 and 5.2, the agglutinated mycelia are concentrated without precipitating, however, which can then give a slight sensation of granularity in the mouth of a taster. The pH at which the sensation of granularity of a milk becomes too noticeable depends on the composition of the milk and the heat treatment to which it was subjected. In a general way, the closer one gets and falls below a pH of 4.9, the more there is a risk of making the milk become unfit for consumption. To regulate the pH of the fermented milk and to conveniently renew the bacterial population that is sensitive to phage attacks (see for this purpose, EP-748871), a pasteurized (non-fermented) milk can be added in the first continuous device. ) and lactic acid bacteria, and the fermented milk of the first device, for example, can be taken continuously. These lactic acid bacteria can be added in the form of a pre-fermented milk which can have a pH lower than 5 and / or which can have at least 107 cfu / g, especially 108-1010 cfu / g, for example. These lactic bacteria can also be added in the form of a culture dried by lyophilization or by spraying under a hot air flow (see for this purpose EP-96201922.0), or in the form of a frozen culture that is concentrated, if appropriate. , before freezing (see for this purpose EP-688864). In order to carry out the present invention, in a second step, the fermented milk taken in continuous from the first device is cooled in a second device at a temperature of less than 15 °, preferably of 2 ° C-10 ° C, such way to subject the fermented milk to a post-acidification; the residence time of that milk in the second device is adjusted so that at the outlet thereof, the pH of the fermented milk is less than 4.7. This second device can also be constituted mainly by at least one refrigerated pipeline; the fermented milk advances continuously in this pipeline by means of appropriate pumps, for example at a flow rate of less than 400 liters per hour; that milk is then subjected to a post-acidification until a pH that can be lower than 4.7 at the outlet of the pipe. Preferably, this particular implementation is applied to fermented milks which, at the outlet of the first device, have a pH of the order of 4.9-5.1, and / or a temperature close to 15 ° C for example of 13 ° C. -20 ° C. To accelerate this post-acidification, it is also possible to regulate the pH of the fermented milk that comes from the first device continuously, by continuously adding an acid composition having a temperature below 15 ° C and a pH below 4.9, but preferably a temperature of the order of 1 ° C-10 ° C and a pH of the order of 2.5-4.7, for example. In this way, the second device can be a refrigerated tank that continuously mixes a fermented milk; the fermented milk taken from the first device is introduced continuously into that tank; an acidic composition is also introduced continuously in that cell in order to accelerate the post-acidification; A fermented milk that has a pH lower than 4.7 is finally taken continuously from this vat. On the other hand, the acid composition may be a milk fermented by lactic acid bacteria but not coagulated. For this, it is enough to previously ferment a milk by lactic acid bacteria to a pH lower than 4.9, for example a pH of 3.9-4.7, without mechanical agitation, in such a way that the syneresis of the milk is avoided, and then to take part continuously of this fermented milk, cool it and add fermented milk to the entrance of the second device, for example. The acid composition can also be a concentrated solution of at least one food acid, such as lactic acid, citric acid and / or malonic acid, for example. Preferably those food acids are used to accelerate the post-acidification of the vegetable-based milks described above. The present invention will be better understood by referring to figures 1 and 2 which schematically represent the devices adapted to the implementation of the present invention. Figure 1 presents 4 double-coat ferretators Fl to F4; each fermenter has a pH probe, the fermenters Fl and F2 also have a volume level probe "LC", and the pH and volume probes of the fermenters Fl and F2 that control the opening of the valves Pl to P5, as indicated by the discontinuous lines. When these devices operate continuously, the pasteurized milk is heated by means of the radiator 1 to the optimum temperature for the growth of the bacteria. This heated milk is then introduced into the fermenter Fl which contains a fermented milk which has a pH higher than the pH at which a perceptible syneresis is triggered. A small amount of starter culture of lactic acid bacteria 2 can also be introduced into the fermenter Fl. Fermented milk is taken from the fermentor Fl, cooled to a cooling temperature by means of a refrigerator 3, and introduced into the refrigerated fermenter F2. To regulate the pH of the fermented milk that is contained in the fermenter F2, a second acid milk cooled by means of the refrigerator 4 is introduced in parallel in the fermenter F2. This second milk comes from one of the two fermenters in alternation. In effect, for each fermenter F3 and F4, in alternation, they are filled with milk heated by means of heater 5, the milk is inoculated by means of the starter culture, the leshe is incubated without agitation at a temperature favorable to bacterial growth up to a pH lower than 4.9, the culture is mixed and taken to introduce it in fermenter F2. When one of the two fermenters F3 and F4 was taken, then the other is filled and then incubated. Finally, a fermented milk with a pH less than or equal to 4.7 and which does not have a texture linked to the appearance of a syneresis of the milk is taken from the fermentor F3. Figure 2 shows a double-coat fermenter Fl comprising a "LC" volume probe and a pH probe; these two probes control the opening of the valves Pl, P2 and P3, as indicated in dashed lines. The device F2 is constituted by a refrigerated chamber that is covered by a long pipe. When these devices operate continuously, the pasteurized milk is heated by means of the radiator 1, at an optimum temperature for the growth of the bacteria. This heated milk is then introduced into the fermenter Fl containing a fermented milk which has a pH just above which a perceptible syneresis is triggered. A small amount of starter culture of lactic acid bacteria 2 can also be introduced into the fermenter Fl. It is taken from fermentor Fl, fermented milk, cooled to a refrigeration temperature by means of a refrigerator 3, and introduced into the pipe at the inlet of device F2. The invention is not limited to the presence of a single pipe in the device F2. The man of the trade can select the number of pipes needed to divide the main flow of fermented milk into several small flows; the diameter of the pipes, their length, the flow rate of the main flow and the cooling temperature, is selected so that the fermented milk can still be post-acidified to a pH less than or equal to 4.7. Finally, a fermented milk having a pH less than or equal to 4.7 and not having a texture linked to the appearance of a syneresis of the milk is taken from the device F2.

The present invention is described in more detail below with the aid of the description supplement which refers to examples for preparing continuous fermented milks. Percentages and parts are given by weight, unless otherwise indicated. Of course, however, that these examples are given by way of illustration of the object of the invention of which they do not constitute, in any way, a limitation.

EXAMPLE l; A yogurt is produced continuously with the help of the devices described in relation to figure 1, and with the help of the strains Streptococcus termophilus CNCM 1-1292 and Lactobacillus bulgaricus CNCM 1-1348, deposited respectively, on August 5, 1993 and March 29, 1993, at the Pasteur Institute, 25, rue de docteur Roux , 75724 Paris. For this, a starter culture of these strains is first prepared, sowing a pasteurized skim milk, supplemented with 0.1% yeast extract, with 3% of a fresh pre-culture of each strain taken at the end of the exponential phase of growth, incubating mix at 43 ° C to a pH of 4.3 (approximately 3.5 hours), and then cool to 10 ° C.

In parallel, a milk comprising 14% dry matter and 2.2% fat is prepared, pasteurized at 105 ° C for 2 minutes, cooled to 70 ° C, homogenized at 300 bar and cooled to 4 ° C. To prepare the production of yogurt in continuous, the fermentor F3 is cooled with 2000 liters of that milk, inoculated with 3% starter culture, incubated without mixing at 43 ° C until a pH of 4-4.1. Then, the fermentor Fl is filled with 80 liters of pasteurized milk, inoculated with 3% of the starter culture, and the milk is incubated at 43 ° C, mixing it until reaching a pH of 5.7. In parallel, fermentor F2 is filled half full with 80 liters of fermented milk and refrigerated at 2 ° C, which comes from fermenter F3. The continuous production of yogurt is started, under the following conditions: the pH in the fermenter is regulated to 5.7 thanks to the controlled action of the valves Pl, P2 and P5 (continuous addition of starter); the first fermented milk that is taken from the fermenter Fl, is cooled to 2 ° C with the help of a refrigerator; the pH of the chilled milk at 2 ° C in the fermenter F2, is regulated to a pH of 4.5 by the controlled addition of fermented milk, refrigerated at 2 ° C, which comes from fermenter F3. While milk is taken from fermenter F3, fermentor F4 is filled with pasteurized milk, sown and incubated until the milk reaches a pH of 4-4.2 (as for fermenter F3). When the fermenter F3 is emptied, the fermented milk is then taken from the fermenter F4, and it is restarted from a culture in the fermenter F3 (use of the fermenters F3 and F4 in alternation). The material flows that are given to the passage through each of the valves Pl to P7, are generally the following: Pl + P5 = P2; P3 = Pl + P5; P5 = 3% of Pl; and P7 = 3% of P6, for example. Finally, a yoghurt having a pH of 4.5 is taken in continuous from the fermenter F2, at a flow rate of the order of 450 liters per hour.

EXAMPLE 2: In the same manner as in Example 1, an acidified milk is prepared with the aid of the probiotic strain Lactobacillus johnsonii CNCM 1-1225 which is described in EP-577904 and of the strain Streptococcus termophilus CNCM 1-1421; those two strains were respectively deposited, on June 30, 1992 and May 18, 1994 at the Pasteur Institute, 25 rue de docteur Roux, 75724 Paris. Unlike the example 1, a carbon dioxide atmosphere is introduced in the fermenters Fl and F2.

The acidified milk obtained in this way presents a texture identical to that of the acidified milk LC1R "natural" (HirtzR, Switzerland), which is a fermented milk prepared in a traditional way with the strain CNCM 1-1225 and a strain Streptococcus thermophilus.

EXAMPLE 3: A yoghurt is continuously produced with the aid of the devices described in relation to FIG. 2, and with the help of the strains Streptococcus thermophilus CNCM 1-1292 and Lactobacillus bulgaricus CNCM 1-1348, respectively deposited, August 5, 1993 and March 29, 1993, at the Pasteur Institute, 25 rue de docteur Roux, 75724 Paris. For this, a starter culture of these strains is first prepared, sowing a pasteurized skim milk, supplemented with 0.1% yeast extract, with 3% of a fresh pre-culture of each strain taken at the end of the exponential phase of growth, incubating mix at 43 ° C to a pH of 4.3 (approximately 3.5 hours), and then cool to 10 ° C. In parallel, a milk comprising 14% dry matter and 2.2% fat is prepared, pasteurized at 105 ° C for 2 minutes, cooled to 70 ° C, homogenized at 300 bar and cooled to 4 ° C.

To prepare the production of yogurt in continuous, the fermentor Fl is filled with 80 liters of pasteurized milk, inoculated with 3% starter culture, the milk is incubated at 43 ° C until reaching a pH of 4.9. Then, the continuous production of yogurt is started, under the following conditions: the pH in the fermenter Fl is regulated to 4.9, thanks to the controlled action of the valves Pl, P2 and P3 (continuous addition of starter); the fermented milk that is taken from the fermenter Fl is cooled to 14 ° C with the help of a refrigerator; the F2 device is cooled to 15 ° C; the length, the diameter, and the flow rate in the pipeline (less than 400 liters per hour) in the device F2 are such that the pH of the fermented milk at the output of the device F2 is of the order of 4.7; the flows of material calculated at the passage of each valve Pl to P3, are in general the following: Pl + P3 = P2; P5 = 3% of Pl. Finally, an acidified milk having a pH of 4.7 is taken continuously from the fermenter F2; that fermented milk presents only a small granularity in the mouth.

EXAMPLE 4: A milk of soybean acidified by the probiotic strain Lactobacillus johnsonii CNCM is continuously prepared 1-1225 with the aid of a device similar to that described in figure 1. For this, a milk comprising 2.9% soybean meal and 14.6% sucrose is prepared in the water. The continuous production of fermented soy milk is started as described in example 1, under the following conditions: the pH in the fermenter Fl is regulated to 5, thanks to the sonometric control of the valves Pl and P2; the first fermented milk taken from the fermenter Fl is cooled to 4 ° C with the help of a refrigerator; and the pH in the fermenter F2, of milk refrigerated at 4 ° C, is regulated to a pH of 3.75 by the controlled addition of a 10% solution of lactic acid, which is contained in the F3 cell (no cell) F4).

Claims (6)

1. R E I V I N D I C A C I O N S 1.- Procedure to prepare a fermented milk continuously in which: - it is prepared in a first device, a milk fermented by lactic acid bacteria; said fermented milk is subjected to mixing and pH conditions such that the syneresis of the milk does not occur, and that pH is regulated by continuous addition of unfermented milk in the first device and continuous intake of fermented milk from the first device; in a second post-acidification device, the fermented milk taken from the first device is cooled to a temperature below 15 ° C in such a way that the fermented milk is subjected to a post-acidification; the residence time of the fermented milk in the second device is adjusted so that, at the outlet thereof, the pH of the fermented milk is less than 4.7; - a fermented milk having a pH lower than 4.7 is taken continuously from the second device.
2. 2. Method according to claim 1, in which lactic acid bacteria are added continuously in the first device.
3. 3. - Process according to claim 2, in which are added continuously, bacteria of a pre-fermented milk having a pH of less than 5.
4. 4. Process according to claim 1, in which, the second device, adjusts the pH of the fermented milk by continuous addition of an acid composition having a temperature lower than 15 ° C and a pH lower than 4.9.
5. 5. The process according to claim 1, wherein the acid composition is selected from the group consisting of a non-coagulated fermented milk and a lactic acid solution of citric acid and malic acid.
6. 6. Method according to any of claims 1 to 5, in which it is prepared continuously, a milk fermented by probiotic lactic bacteria that can adhere to human intestinal cells, exclude pathogenic bacteria on human intestinal cells and act on the immune system human allowing him to react more strongly against external aggression.