WO2001044440A1

WO2001044440A1 - Method for obtaining a powder containing viable microorganisms, powder obtained according to this method and device for carrying out said method

Info

Publication number: WO2001044440A1
Application number: PCT/FR2000/003492
Authority: WO
Inventors: Pierre Schuck; Patrick Lucien Gas Boyaval
Original assignee: Institut National De La Recherche Agronomique (Inra)
Priority date: 1999-12-13
Filing date: 2000-12-12
Publication date: 2001-06-21
Also published as: FR2802212A1; AU2855501A; FR2802212B1

Abstract

The invention relates to a method for producing a powder which contains viable microorganisms and which has a long storage life, by atomization. The invention also relates to a dry powder which contains viable microorganisms, which has a long storage life and which is produced according to the inventive method. Finally, the invention relates to a device for producing a powder which contains viable microorganisms and which has a long storage life, by atomization.

Description

Process for obtaining a powder containing viable microorganisms, powder obtained by this process and device for its implementation.

The invention relates firstly to a process for the preparation by atomization of a powder containing viable microorganisms with a long shelf life.

The subject of the invention is also a dry powder containing viable microorganisms with a long shelf life, capable of being obtained by the process of the invention.

The present invention also relates to a device for the manufacture by atomization of a powder containing viable microorganisms and with a long shelf life. Many sectors of the industry have long used the use of microorganisms, because of the capacity of microorganisms to produce enzymes catalyzing the synthesis of products of interest or their capacity to directly produce metabolites of industrial interest. For example, the agro-food industries conventionally use microorganisms in biotransformation processes of agricultural products, such as for example the dairy or cheese industry, the delicatessen industry, the biomass-producing industries ( for example making sourdough). Many types of microorganisms are also used in processes for the synthesis of organic products, such as alcohols, various solvents or organic acids.

The pharmaceutical industry is also increasingly using microorganisms, where appropriate recombinant microorganisms, in order to produce molecules of therapeutic interest, such as vitamins, vaccines, cytokines or hormones.

There is thus a need in industry for a raw material containing viable microorganisms, easily transportable, the storage conditions of which are simple, having a high density of viable microorganisms and which can furthermore be stored for a long time. without significant reduction in the Tiber no of starting microorganisms.

It is moreover highly desirable that the raw material containing the microorganisms be as small as possible in order to limit the costs of storage and transport. Conventionally, the preparation of a biomass involves a multiplication of the microorganisms in fermenters according to a continuous or discontinuous process, then a separation and a concentration of the microorganisms by centrifugation (separation by density difference), or even by ultrafiltration or membrane microfiltration, for example by membranes having cutoff thresholds between 300,000 and 500,000 Daltons (Lejard et al., 1994 in Lactic bacteria, page 539, vol.l., Lorica).

Centrifugation and membrane separation techniques lead to an increase in cell density of 10 to 50 times (Branger et al., 1994 in Lactic bacteria p. P.523-537, vol.1, LORICA).

The concentrated ferments thus obtained are marketed either as is or in frozen form after most often adding cryoprotectors such as sucrose, trehalose, small peptides, glutamate, ascorbate or even magnesium salts. .

However, the storage of microorganisms in frozen form requires strict compliance with the cold chain.

Conventionally, freezing is done by the use of liquid nitrogen and the storage as well as the transport require the maintenance of a temperature lower than - 60 ° C.

The storage of concentrated microorganisms in the form of frozen raw material is complex and expensive because of the need to keep this raw material at low temperature.

After concentration, the raw material containing microorganisms can also be stored at a temperature close to

3 ° C to 4 ° C after lyophilization. However, the cost of the lyophilization step is high and the cost price of the lyophilized raw material is not very compatible with the constraints of the industry.

Another approach consists in dehydrating a medium with a high density of microorganisms, the dehydration step being able to be carried out on a fluidized bed or even by atomization.

Dehydration of sourdoughs in the atomization tower is a technique that has been widely used in the dairy industry (Bullock L. and JW Lightbrown, 1947 Quart. J. Pharm. Pharmaco., 20: 312. The article by Péri et al. (Péri C. and C. Pompei, 1976, Riv. Sci. Tecn. Alim. Nutr. UM., Pages 231-236) describes a process for obtaining a powder containing lactic acid bacteria obtained by dehydration in a tower of atomization. According to this article, a survival rate of bacteria

5 lactic acid contained in a yogurt powder dehydrated by atomization is low, and at most of the order of 50% of the viable starting microorganisms after 120 days of storage at a relative humidity of 23%.

The article by Brajapati et al. (Brajapati J.B. et al., 1987, Australian

IO Journal of Dairy Technology, March / June: pages 17-21) is a study concerning the survival rate of bacteria of the Lactobacillus acidophilus type contained in a spray-dried powder based on fermented milk in the presence of banana, tomato juice and sugar. In this case, a maximum survival rate of microorganisms is observed

15 approximately 66% after storage for two months in sealed polyethylene bags at a temperature between 28 and 31 ° C and at a humidity of 4.82%.

The article by Abd el Gawad et al. (1989, Egyptian J. Dairy, sci., Vol.17: 273-281) studies the effect of the culture conditions of microorganisms

20 prior to spray drying. This article describes survival rates of microorganisms in the product directly obtained at the end of the spray dehydration step, respectively 30% for S. lactis, 76% for S. thermophilus and 31% for L. bulgaricus. In addition, survival rates of these different microorganisms after 30 days of

Storage in sealed polyethylene bags was reduced to 3.6%, 7% and 1.18% respectively when the storage temperature was between 20 and 25 ° C.

The article by Espina (Espina F and V.S. Packard, 1979, Journal of Food Protection, vol. 42 (2): 149-152), relating to obtaining milk powders

30 skimmed containing lactic acid bacteria dehydrated by atomization, specifies that the survival rate of the microorganisms directly resulting from the dehydration stage by atomization is at most 10% of the viable microorganisms before dehydration. On the other hand, an additional reduction of 50% in the survival rate is observed after conservation powder obtained according to the method described in this article in airtight polyethylene bags for 30 days at a temperature of 4 ° C.

The article by Miller et al. (Miller D.L et al., 1972, Journal of Food Science, vol.37: 828-831) relates to a study of the survival rate of bacteria of the genus Salmonella and Escherichia coii after dehydration of a milk concentrate by atomization. The results described in this article indicate a reduction in the number of viable microorganisms ranging from 100 times to 1000 times for bacteria of the genus Salmonella and Escherichia coii. The dehydration processes by atomization described in the above articles are conventionally carried out by atomization of a liquid medium concentrated in microorganisms in the presence of a stream of hot air at the top of an atomization tower, the product atomized and dehydrated being collected at the base of the atomization tower. Such a process is also described in PCT application No. WO 98/10

665 on behalf of Société des Produits Nestlé SA According to the dehydration process described in this application, the inlet temperature of the hot air is around 300 ° C, the outlet temperature of the hot air is about 65 ° C and the percentage of humidity of the powder obtained after dehydration is between 3.5 and 4%. At the end of the dehydration stage, a survival rate of lactic acid bacteria of about 6% is observed. The powder obtained after atomization is collected directly on a fluidizer and heated to temperatures ranging from 60 to 90 ° C in order to complete the dehydration. It follows from the studies described above that the methods for dehydrating a medium concentrated in microorganisms of the prior art led to a high mortality of the microorganisms during the dehydration step itself, the powders obtained according to the processes of the state of the art do not exhibit a lasting maintenance of the viability of the microorganisms of the dehydrated material, even under conditions of storage at low temperature.

The applicant set out to develop a new process for dehydrating a liquid medium containing microorganisms with the aim of obtaining a powder having a maximum survival rate of the microorganisms initially present in the liquid medium, said powder being furthermore capable of being preserved durably without significant reduction in the number of viable microorganisms and without physiological alteration of these microorganisms.

It has been shown according to the invention that an increased survival rate of the microorganisms at the end of the atomization step could be obtained by reducing the inlet temperature of the hot gas, compared with the methods of l 'state of the art.

By hot gas, within the meaning of the invention, is preferably meant air or nitrogen. Nitrogen is preferably used for the production of a powder containing anaerobic microorganisms or even when less oxidation of the components of the liquid medium containing the microorganisms is sought.

However, the applicant has also observed that the decrease in the inlet temperature of the hot gas, due to a less energy transfer between the stream of hot gas and the atomized droplets of liquid medium containing the microorganisms, led incomplete dehydration and obtaining a moist paste, not a powder.

This dough cannot be easily worked and is also not likely to be subsequently fluidized in the form of a powder. This would result in difficult packaging and transport.

In addition, if the survival rate of the microorganisms initially contained in the concentrated liquid medium is high, the humidity level of the dough, which is around 5 to 15%, is detrimental to long-term storage microorganisms, even at a temperature of 4 ° C.

In order to solve this technical problem, the applicant has developed a method in which the friable paste obtained at the end of the atomization step is collected on a drying member before any subsequent treatment. The drying stage makes it possible to lower the percentage of humidity of the product directly resulting from the atomization stage and then makes it possible to manufacture a dry powder containing viable microorganisms capable of being preserved in the long term .

A first object of the invention therefore consists of a process for obtaining a powder containing viable and lasting microorganisms long storage, by atomization of a liquid medium containing the micro-organisms, characterized in that the atomization step is carried out under conditions making it possible to obtain an atomized product whose moisture content is between 5% and 15%, preferably between 7% and 10% approximately and is followed by a step of drying the atomized product.

The step of atomizing the liquid medium containing the viable microorganisms is preferably carried out cocurrently in a hot gas (air or neutral gas such as nitrogen) under pressure.

Preferably, the liquid medium containing the microorganisms comprises between approximately 10 ⁷ and 10 ¹² and even more preferably from 10 ⁹ to 10 ¹¹ viable cells of microorganisms per milliliter.

According to a particular embodiment of the method of the invention, the liquid medium containing microorganisms consists of a milk food containing one of the viable bacteria with probiotic effect, said food corresponding to specific nutritional needs of the population (children or the elderly). By way of nonlimiting example, the bacteria with probiotic effect added to milk formulations before drying according to the present invention can be of the genus Bifidobacterium, Lactobacillus, Propionibacterium. Preferably, the liquid medium containing the viable microorganisms and the hot gas are brought to the top of the atomization tower.

According to an advantageous aspect of the method according to the invention, the temperature of the gas at the inlet of the atomization tower is between 100 ° C and 180 ° C, and preferably between 120 ° C and 140 ° C.

According to another advantageous aspect of the process according to the invention, the temperature of the gas at the outlet of the atomization tower is between 30 ° C and 80 ° C, and preferably between 40 ° C and 60 ° C.

According to yet another aspect, the flow of hot gas at the inlet of the atomization tower is between 3500 and 6000m ³ / h, and is preferably around 5000m ³ / h.

The inlet pressure of the liquid medium containing the microorganisms at the top of the atomization tower is preferably between 8 and 18MPa, and preferably between 10 and 12MPa. Most preferably, the step of atomizing the liquid medium containing the microorganisms leads to the formation of a crumbly paste, which is collected on a drying member.

According to a first alternative, the drying of the atomized product in the drying member is carried out without heating.

According to a second alternative, the drying of the atomized product is carried out with heating. It is preferably a moderate heating operation, more particularly when the liquid medium containing the microorganisms contains hygroscopic components. As already indicated above, the drying step is carried out downstream from the outlet of the atomization tower, that is to say at a temperature significantly lower than the outlet temperature of the hot gas from the atomization tower .

For example, it has been observed that when the process is carried out with air and at an inlet temperature of the hot air from the atomization tower of 180 ° C., the temperature of the air directly in contact with the friable dough at the level of the drying member is lowered to its wet temperature of 45 ° C 1 2 ° C, that is to say to a temperature at which the mortality of microorganisms is very reduced . Preferably, the temperature of the gas during the drying step is at least 25 ° C lower, preferably at least 30 ° C than the air temperature at the outlet of the atomization tower observed according to the state of the art processes.

Advantageously, the drying step is carried out using a drying member such as a rotary disc or a conveyor belt.

Preferably, the duration of the step for drying the atomized product is between 5 and 30 minutes, preferably between 10 and 20 minutes.

As already indicated, the original characteristics of the process for obtaining by atomization of a powder containing viable microorganisms according to the invention, now allow those skilled in the art to prepare a raw material rich in microorganisms, easily transportable, and which can be stored long term and at room temperature without significant reduction in the number of micro- viable organisms found in this raw material directly after the process.

The advantageous characteristics of the powder obtained by the implementation of the above process result from the fact that only partial dehydration of the liquid medium concentrated in microorganisms is carried out during the atomization step, thus significantly reducing mortality microorganisms compared to the processes of the state of the art in which is sought an advanced dehydration of the liquid medium containing the microorganisms during atomization. In addition, the step of drying at a low temperature and lower than the outlet temperature of the hot air does not appreciably affect the viability of the microorganisms initially present in the friable dough collected on the drying member, while allowing a more complete dehydration of the atomized product which then passes from the state of crumbly dough to the state of powder having a low level of humidity.

As indicated above, the moisture content of the atomized product at the end of the atomization step is between 5% and 15%, preferably between 7% and 10%.

In addition, the moisture content of the powder obtained at the end of the drying step is between 6% and 9%.

The low humidity of the powder at the end of the drying step is particularly advantageous, because it allows subsequent treatments of the powder without appreciable damage to the viability of the microorganisms. Preferably, the powder obtained at the end of the drying step is then fluidized and undergoes final dehydration by heating, such subsequent dehydration by heating of the previously dried powder does not appreciably affect the viability of the microorganisms of the made of the low initial humidity of the powder at the start of the fluidization stage and the better resistance to thermal stress of partially dehydrated microorganisms.

Preferably, the fluidization is carried out on a vibro-fluidizer comprising a heating means.

According to the process, the fluidized powder can undergo a grinding step. According to a particularly advantageous embodiment of the method according to the invention, the liquid medium containing the viable microorganisms comprises a high proportion of lactose, preferably approximately 15 to 30% of lactose by total weight of the liquid medium. Lactose, contained in high proportions in milk, is well known for its hygroscopic properties and is consequently difficult to dry, except in the case where lactose can be obtained in crystallized form, in which case its hygroscopic properties are greatly reduced. It has been observed according to the invention that, when the liquid medium containing the viable microorganisms comprises a high proportion of lactose, the drying step subsequent to the atomization step allows the crystallization of the lactose and thus greatly reduces the hygroscopic properties of the powder obtained at the end of the drying step, which has the effect of facilitating the subsequent treatments of fluidization and advanced dehydration, on the one hand, and on the other hand, of facilitating the long-term conservation.

According to an advantageous aspect of the method according to the invention, it is further characterized in that the liquid medium containing the viable microorganisms comprises between 15% and 30% of lactose, by total weight of the liquid product.

Other crystallizable sugars can also be used in the same proportions as lactose, such as sucrose, dextrose or even malto-dextrins. In such an embodiment, the method is further characterized in that the step of drying the atomized product is accompanied by crystallization of the crystallizable sugar contained in the latter.

The microorganisms used in the process of the invention can be of any kind. They can in particular be indifferently bacteria or yeasts.

The bacteria can be, for example, lactic acid bacteria, such as the strains of lactic acid bacteria described in PCT application No. WO 98 / 10.666, the relevant passage of which is incorporated herein by reference. It can also be propionic bacteria. It can also be bacteria whose multiplication is sought for the production of antigens for vaccines, for the production of enzymes catalyzing the biotransformation of compounds of industrial interest, or even for the direct production of metabolites used in l 'industry.

They may also be microorganisms transformed by genetic engineering and capable of expressing recombinant proteins, such as enzymes, or else metabolites of industrial interest, for example of therapeutic interest, such as vitamins, antigens, cytokines or hormones.

Among the yeasts capable of being treated by the process according to the invention, mention may be made of yeasts used in the baking industry, such as the strains of Saccharomyces cerevisiae.

They can also be unicellular algae cells producing metabolites conferring resistance to osmotic or thermal stress, such as glycine-betaine, and which can be incorporated into products for animal or human food or used directly as nutritious supplements. They may in particular be unicellular algae cells such as Spirulina scenedesmus, Chlorella diatomae or even Dunaliella.

Due in particular to the low mortality of microorganisms observed during the implementation of the method according to the invention, it is now possible to obtain a dry powder containing microorganisms with high cell density, more particularly a dry powder containing from 10 ⁷ to 10 ¹² viable microorganisms per gram of dry matter, as measured according to the method by drying in an oven (102 ° C - 105 ° C) to constant mass.

It has also been shown according to the invention that the dry powder obtained according to the above process could be stored for more than six months without the viability of the microorganisms being significantly affected.

Thus, it has been observed according to the invention that 82% of the microorganisms found in the dry powder at the end of the above process were still present after storage of the dry powder for six months at a temperature of 7 ° C. in aluminum bags. In addition, the viable microorganisms contained in the dry powder obtained by the process of the invention have not undergone any alteration in their physiological capacity, as evidenced by the fact that no significant increase in the multiplication time does has been observed after storage.

Another object of the invention consists of a dry powder containing from 10 ⁷ to 10 ¹² viable microorganisms per gram of dry matter, preferably containing from 10 ⁹ to 1 0 ^{1 1} viable microorganisms per gram of dry matter. The above dry powder is further characterized in that it has a humidity level of between 3% and 7%, as measured by drying in an oven to constant mass.

The number of viable microorganisms found in the dry powder obtained according to the invention, after being stored in the air protected for six months at a temperature between 7 and 17 ° C is at least

70%, preferably at least 80% of the number of starting microorganisms.

The dry powder according to the invention is also characterized in that it comprises from 60% to 70% of sugar in crystallized form. The dry powder according to the invention is further characterized in that it has a solubility in distilled water greater than 99%, preferably greater than 99.5%.

According to yet another aspect, the dry powder has a dispersibility index greater than 90%, preferably at least 95%. According to an advantageous characteristic, the dry powder has a wettability time of at most 10 seconds, preferably at most 7 seconds.

According to another advantageous characteristic, the particle size of the dry powder according to the invention is between 1 μm and 40 μm approximately.

The invention also relates to a composition intended for seeding a product with a view to the multiplication of microorganisms, characterized in that it comprises a dry powder as described above, or consists of the dry powder. The invention also relates to a product for human or animal consumption, characterized in that it is seeded with a composition or a dry powder above. The invention also relates to a product intended for human or animal consumption, characterized in that it comprises or consists of a dry powder as described above.

Such a product for human or animal consumption can be a

5 fermented milk, sourdough or fermented drink.

It can for example be a dried yoghurt or a dried fermented milk.

It may also be a milk product intended for feeding infants, babies or young children, in which case the dry powder

IO obtained according to the process described above comprises from 10 ⁴ to 10 ¹² viable microorganisms, preferably microorganisms with probiotic activity, per gram of dry matter. Such a powder obtained according to the process of the invention is also characterized by the low number of non-viable microorganisms per gram of dry matter, which is not the case.

15 case of dry powders manufactured according to the methods of the prior art as results from the results presented in the examples.

The applicant has also developed a device comprising an appropriate drying means, suitable for carrying out the above process.

Another object of the invention consists of a device for the manufacture by atomization of a powder containing viable microorganisms with a long shelf life, comprising an atomization tower, characterized in that said device comprises an organ dryer placed downstream of the atomization tower.

The single figure represents by way of illustration and in no way limitative the diagram of a device for the manufacture by atomization of a powder containing viable microorganisms according to the invention.

Preferably, the drying member (1 1) is placed directly at the base of the atomization tower (7). So the droplets of the liquid medium

30 containing the microorganisms, produced by atomization and partially dehydrated by transfer of water from the droplet to the stream of hot gas during their stay in the atomization tower (7), are collected directly at the base of the tower ( 7) on the drying member (1 1).

Preferably, the drying member is devoid of any

35 heating means. Drying is carried out by simple contact of the dough friable collected on the drying member (11) with the air circulating directly downstream of the base of the atomization tower (7) whose temperature is lower than the outlet temperature of the hot gas from the atomization tower . However, a heating means can be provided, in particular when the liquid medium containing the microorganisms contains hygroscopic constituents and the drying step must be pushed. Such a heating means can be a means for circulating hot gas similar to the heating means (14) used for the fluidization means (15).

According to a first aspect, the drying member (11) consists of a rotating disc. It is preferably a rotary disc which can be confined in a closed enclosure, in particular made of stainless steel.

The rotary disc is connected to a variable speed motor which makes it possible to adjust the speed of rotation of the disc appropriately and thus to define the residence time of the atomized product on the drying member before any subsequent treatment.

According to a second aspect, the drying member (11) is a conveyor belt, preferably a perforated conveyor belt of the “Filtermat” type sold by the company Niro Atomizer or else of the “Jet Belt Dryer” type sold by the Company Technic Process , or any other means with equivalent characteristics.

By any other means of equivalent characteristics, is understood within the meaning of the present invention, a member capable of collecting the atomized product downstream of the atomization tower (7) and of keeping the atomized product in contact with the hot gas circulating downstream of the atomization tower in order to complete the dehydration of the atomized product to a maximum level of humidity chosen, before any subsequent treatment of the resulting dehydrated powder.

According to an additional characteristic, the device for the manufacture by atomization of a powder containing viable microorganisms according to the invention comprises, downstream of the drying member (11), means (15) for fluidizing the powder dried.

Preferably, the means (15) for fluidizing the dry powder is a vibro-fluidizer, well known to those skilled in the art.

Preferably, the vibro-fluidizer is provided with a heating means (14), as well as a fan (13). A means of transport (18) of the dry powder can be arranged between the drying member (11) and the means (15) of fluidization of the dry powder.

A grinder (23) can be arranged downstream of the fluidization means (15).

The device according to the invention can also comprise a set of means intended to ensure the atomization of the liquid medium containing the viable microorganisms. The device is therefore further characterized in that the atomization tower (7) comprises:

• a means (6) for supplying pressurized hot gas situated at the top of the atomization tower (7);

• a means (2) for the arrival under pressure of a liquid medium containing viable microorganisms and opening onto a nozzle (3) located at the top of the atomization tower (7).

The hot gas stream is created by means (4), which can be an air fan.

The atomization tower (7) further comprises means (19) for evacuating the hot gas loaded with particles of partially dehydrated atomized product, located at the top of the atomization tower.

According to a particular embodiment of the device according to the invention, the means (19) for discharging the hot gas loaded with particles of partially dehydrated atomized product is connected to a means for recycling said particles comprising a pipe (16) arriving at the top of the atomization tower (7).

According to an alternative, the pipe (16), or a derivation thereof, can lead to the drying member (11), this alternative not being shown in the single figure. A booster (12) circulates the recycled powder particles to the top of the atomization tower (7).

The means for recycling the particles of partially dehydrated atomized product may further comprise a cyclone-effect device (8) at the top of which opens the means (19) for evacuating the hot gas loaded with particles and connected at its base to the pipe ( 16). Such a cyclone-effect device makes it possible, by density difference, to separate the partially dehydrated powder particles which descend by gravitation to the base of the cyclone-effect device (8) and which can be recycled to the atomization tower (7) through the pipeline (16),

5 when the valve (17) is open.

The cyclone effect device (8) may include at its top a suction means (20).

In addition, a pipe (24) in which the hot gas from the fluidization means (15) circulates leads to the suction means I O (20).

The suction means (20) can be a pipe connected to the top of a second cyclone-effect device (9), itself connected by its base to the pipe (16) by which the particles of partially dehydrated atomized product can be recycled by reintroduction to the top of the atomization tower (7). A valve (21) is placed at the base of the cyclone effect device (9).

Downstream of the cyclone effect device (9) a fan (10) sucks in the outlet gas and thus creates an air depression.

According to a particular aspect of the device according to the invention, the means 20 (2) for arriving under pressure of the liquid medium containing the viable microorganisms comprises a feed pump (1).

A means for heating (22) the liquid medium containing the microorganisms can be placed upstream of the feed pump (1).

According to another particular aspect of the device according to the invention, the means (2) for arriving under pressure of the liquid medium containing the viable microorganisms also comprises a thermal regulation means (22).

The invention is further illustrated, without however being limited, by the examples below. 30

EXAMPLES:

The examples of implementation of a process according to the invention have all been carried out on a device comprising a tower

35 three-stage atomization of the brand NIROATOMIZER MSD, evaporative capacity of 50 to 70 kg of water per hour, equipped according to the invention with a drying member consisting of a rotating Niro Kestner crystallization disc.

EXAMPLE 1: Dehydration by atomization and drying of propionic bacteria.

1.1 Preparation of the liquid medium containing the microorganisms.

300 liters of Propionibacterium acidipropionici (strain ATCC 4965) in suspension, concentrated to 5.4 × 10 ¹⁰ CFU / ml by ultrafiltration using positive pumps and mineral membranes, M1 (70,000 Da and sold by the Company Tech- Sep, France, surface: 6.8 m ² ) were used for each of the experiments.

The bacterial concentrate was mixed with a 50% dry matter concentrate of sweet whey, obtained from cooked whey powder from pressed pressed cheeses (homogeneous batch, human quality, Entremont) and then dissolved in water beforehand. filtered through a 0.2 μm pore size membrane, then heated to 70 ° C to facilitate its dissolution and then cooled to 20 ° C.

The cell concentration of the mixture was 5.5 × 10 ⁹ CFU / ml and the pH of the suspension was 5.7 × 0.1. The dry extract was 322 g / kg. (The cell density was therefore 1, 7.10 ¹⁰ CFU / g of dry matter)

1.2 Atomization and drying

The following drying parameters were applied: inlet air temperature 120 ° C, outlet air temperature 40 ° C, nozzle supply pressure 10MPa, speed of rotation of the finisher disc

0.2 rpm. The nozzle used had a diameter of 0.73 mm, the needle was No. 421 allowing a spray angle of 60 °.

The powders obtained were stored in aluminum bags at 7 and 17 ° C for 6 months. 1.3. Viability of microorganisms.

Immediately after manufacture, 1.7 x 10 ¹⁰ CFU / g were counted in the powder, which indicates a viability of 100%. The humidity of the powder was 6.8%. The powder had a solubility greater than 99.5%. The dispersibility of this powder was 98.5%. The wettability index was

6 seconds. The particle size was between 40 μm and 1 mm.

The methods for measuring humidity, dispersibility, wettability index and particle size were those described in the NIRO ATOMIZER 4th ed. 1978. The solubility measurement was that recommended by the ADPI (1990) Bulletin 916.

After 6 months of storage at 7 ° C, a viability of 82% was counted in the powder.

The FMAR aerobic revivable mesophilic flora was determined on PCA (Difco) according to the method known to those skilled in the art.

The propionibacteria were determined as described in French patent 93 00 823 after reconstitution of the powders as follows: 10 g of powder were added to a sterile solution composed of 90 ml of distilled water, 1 g of peptone (Difco, USA) and 0.765g of NaCI. The pH was adjusted to 7.0. The mixture was maintained at 37 ° C-30 min. and homogenized for 3 min in STOMACHER equipment (Labo Blender, U.K.).

EXAMPLE 2 Dehydration by atomization and drying of propionic bacteria (2nd embodiment).

The bacterial concentrate was prepared in accordance with the teaching of Example 1 above.

The initial bacterial concentrate had a viability of 2.9 x 10 ¹⁰ CFU / g. The cell concentration of the mixture with whey was 3.10 ⁹ CFU / ml, but the dry matter content of said mixture was increased to 461 12 g / kg.

2.1 Atomization and drying. The following drying parameters were applied: inlet air temperature 1 15 ^C C, outlet air temperature 50 ° C. Nozzle supply pressure 17MPa, rotational speed of the finisher disc

0.2 rpm. All the other parameters were identical to those of Example 1.

2.2 Viability of microorganisms

The final powder obtained during manufacture had a population of 9.4 x 10 ⁸ CFU / g. The humidity of the powder was 4% due to the increase in the air outlet temperature.

The powder had a solubility greater than 99.5%. The dispersibility of this powder was 95%. The wettability index was 10 seconds. The particle size was between 40 μm and 1 mm. The viability percentage was 14%.

After 6 months of storage at 7 ° C, a population of 7.10 ⁸ CFU / g was counted, which represents a viability of 74%.

EXAMPLE 3 Drying by atomization of lactic acid bacteria (1st embodiment).

3.1 Preparation of the liquid medium containing the lactic acid bacteria.

An industrial strain of Lactobacillus plantarum has been studied.

The multiplication of the cells was carried out according to conventional procedures for the production of industrial leaven. This strain has significant mortality (> 90%) during its drying by lyophilization. The cell suspension (570 kg 110 kg) concentrated by centrifugation was placed in plastic containers of approximately 60 kg, without prior neutralization.

3.2. Atomization and drying.

The bacterial concentrate was mixed with a 50% dry matter concentrate of sweet whey. The following drying parameters have applied: inlet air temperature 140 ° C, outlet air temperature 58 ° C, supply nozzle pressure 12MPa, speed of the finisher disc 0.2 rpm.

The nozzle used had a diameter of 0.78 mm, the needle was No. 421 allowing a spray angle of 62 °. All other parameters were identical to the previous examples.

The powder was then stored at 7 ° C in aluminum bags for viability monitoring for 9 months.

The bacterial concentrate had a cell density of 1.7 x 10 10 ¹¹ CFU / g to 1.5 x 10 ¹¹ CFU / g. The pH of the suspension was 5.85 1 0.02 during the tests. The dry matter content was 360 g / kg.

A powder containing 1.3 × 10 ¹⁰ revivable cells per gram of dry matter was obtained. The powder had a solubility greater than 99.5%. The wettability index was less than 5 seconds. These results are explained by the presence on the one hand of high density particles and on the other hand, by the presence of whey which promotes the wettability of the powders.

3.3 Viability of lactic acid bacteria 0

After 3 months of storage at 7 ° C, viability was maintained but the cell density dropped to 14% of the cell density of the initial powder after 9 months of storage at 7 ° C.

EXAMPLE 4: Spray drying of lactic acid bacteria (2nd embodiment).

The preparation of the liquid medium containing the lactic acid bacteria is carried out in accordance with the teaching of Example 3.

_> o

4.1 Atomization and drying.

Reincorporation of whey powder into the bacterial concentrate.

^• The following drying parameters were applied: inlet air temperature 125 ^C , outlet air temperature 58 ° C, pressure of the feed nozzle 12MPa, speed of rotation of the finisher disc 0.2 rpm. The nozzle used had a diameter of 0.78 mm, the needle was No. 421 allowing a spray angle of 62 °. All the other parameters remained identical to the previous examples. Dry extract of the mixture: 474 1 2 g / kg. The powder is then stored at 7 ° C in aluminum bags for viability monitoring for 9 months.

This test gave the best results with 2.9 x 10 ¹⁰ revivable cells per gram of dry matter. The re-incorporation of the whey powder directly into the concentrate made it possible to achieve a high dry matter content in the product before drying (470 g / kg). The increase in this content improved drying, the inlet air temperature could be lowered from 140 to 125 ° C. This decrease was favorable to maintaining the viability of the microorganisms. In addition, the supply of water to dry on the tower was limited (120 kg of water) which leads to energy savings. The humidity of the powder was 4%. The powder had a solubility greater than 99.5%. The wettability index was less than 5 seconds. These results are explained by the presence on the one hand of high density particles and on the other hand, by the presence of whey which promotes the wettability of the powders.

4.2 Viability of lactic acid bacteria.

Microbiological examination of the powders showed an absence of Clostridium sulphito-reducing agents and a Coliform flora of less than 10 germs per gram.

The conservation of these microbial powders showed a total maintenance of the viability after 3 months at 7 ° C and a conservation of 66% compared to the viability of the initial powder for the powder after 9 months. The lactic acid bacteria were counted on MRS agar medium after 24 h at 30 ° C (de Man et al., 1960) on the powder sample reconstituted as described above.

Clostridium sulfito reducers were counted on VF medium and conform on URBL medium according to procedures known to those skilled in the art.

EXAMPLE 5: Drying by atomization of bifidobacteria: preparation of a dried milk food.

5.1. Microorganism strain.

The dehydration of a formulation containing a strain of Bifidobacterium has been studied. This strain is marketed by the company Chr. Hansen, lot number DN 156007/92618 (Best before: 12.07.00) and was kept for 3 weeks at -20 ° C.

5.2. Atomization and drying.

148.5 kg of bacterial concentrate were mixed with 250 kg of soft whey concentrate with 58% dry matter. The drying parameters used were: inlet air temperature 135 ° C, outlet air temperature 61 ° C, pressure of the supply nozzle 15 MPa, speed of rotation of the supplier's disc 0.2 rev / min. The nozzle used had a diameter of 0.78 mm, the needle was No. 421 allowing a spray angle of 62 °. All other parameters were identical to the previous examples.

The cell density of the mixture was between 2 x 10 ⁹ CFU / g and 3.1 x 10 ⁹ CFU / g. The pH of the mix was 5.73 + 0.02. Its dry matter content was 396 g / kg.

The powder obtained, containing a high cell density of bifidobacteria, had a solubility greater than 99.5%. The wettability index was less than 5 seconds.

Claims

claims

1. Method for obtaining a powder containing viable microorganisms and with a long shelf life, by atomization of a liquid medium containing the microorganisms, characterized in that the atomization step is carried out under conditions making it possible to obtain an atomized product whose moisture content is between 5% and 15%, preferably between 7% and 10% approximately, and is followed by a step of drying the atomized product.

2. Method according to claim 1, characterized in that the atomization of the liquid medium containing the viable microorganisms is carried out co-current in a hot gas.

3. Method according to one of claims 1 or 2, characterized in that the liquid medium and the hot gas are introduced at the top of an atomization tower.

4. Method according to one of claims 1 to 3, characterized in that the temperature of the gas at the inlet of the atomization tower is between 100 ° C and 180 ° C, preferably between 120 ° C and 140 ° vs.

5. Method according to one of claims 1 to 4, characterized in that the temperature of the gas leaving the atomization tower is between 30 ° C and 85 ° C, preferably between 40 ° C and 60 ° C .

6. Method according to one of claims 1 to 5, characterized in that the gas flow at the entrance of the atomization tower is between 3500 and 6000 m ³ / h.

7. Method according to one of claims 1 to 6, characterized in that the inlet pressure of the liquid medium containing the microorganisms at the top of the atomization tower is between 8 and 1 8 MPa, preferably between 10 and 12 MPa.

8. Method according to one of claims 1 to 7, characterized in that the step of drying the atomized product is carried out with or without heating, using a drying member such as a rotary disc or a conveyor belt.

9. Method according to one of claims 1 to 8, characterized in that the duration of the step of drying the atomized product is between 5 and 30 minutes, preferably between 10 and 20 minutes.

10. Method according to one of claims 1 to 9, characterized in that the liquid medium containing the viable microorganisms comprises between

15% and 30% of a crystallizable sugar, by total weight of the liquid medium.

11. Method according to claim 10, characterized in that the step of drying the atomized product is accompanied by a crystallization of the sugar contained therein.

12. Method according to one of claims 1 to 11, characterized in that the dry powder obtained at the end of the drying step has a humidity level of between 3% and 7%, as measured by desiccation in the oven until constant mass.

13. Method according to one of claims 1 to 12, characterized in that the atomized and dried powder is then fluidized.

14. Method according to one of claims 1 to 13, characterized in that the fluidized powder undergoes a grinding step.

15. Method according to one of claims 1 to 14, characterized in that the microorganisms are bacteria, preferably lactic acid bacteria, Propionibacteria.

16. Method according to one of claims 1 to 15, characterized in that the liquid medium comprises between approximately 10 ⁷ and 10 ¹² viable microorganisms per milliliter.

17. Dry powder containing 10 ⁷ to 10 ¹² viable microorganisms per gram of dry matter.

18. Dry powder obtained by the method according to one of claims 1 to 15 characterized in that it contains from 10 ⁴ to 10 ¹² viable microorganisms with probiotic properties per gram of dry matter.

19. Dry powder according to one of claims 17 and 18 comprising from 60% to 70% sugar in crystallized form.

20. Dry powder according to one of claims 17 to 19 characterized in that it has a humidity level between 3% and 7%, as measured by drying in an oven to constant mass.

21. Dry powder according to one of claims 17 to 20, characterized in that the number of viable microorganisms after one storage away from air for 6 months at a temperature between 7 and 17 ° C is at least 70%, preferably 80% of the number of microorganisms in the initial dry powder.

22. Composition intended for the inoculation of a product with a view to the multiplication of microorganisms, characterized in that it comprises a dry powder according to one of claims 17 to 21.

23. Product for human or animal consumption, characterized in that it is seeded with a powder according to one of claims 17 to 21 or with a composition according to claim 22.

I O 24. Product for human or animal consumption, characterized in that it comprises or consists of a dry powder according to one of claims 17 to 21.

25. Product according to claim 23 or 24, characterized in that it is a fermented milk, a sourdough or a fermented drink.

26. Device for the atomization production of a powder containing viable microorganisms with a long shelf life, comprising an atomization tower (7), characterized in that said device comprises a drying member (11) placed downstream of the atomization tower.

27. Device according to claim 26, characterized in that the drying member (1 1) is arranged at the base of the atomization tower.

28. Device according to one of claims 26 or 27, characterized in that the drying member is devoid of heating means.

29. Device according to one of claims 26 or 27, characterized in that the drying member comprises a heating means.

25 30. Device according to one of claims 26 to 29, characterized in that the drying member (1 1) consists of a rotating disc.

31. Device according to one of claims 26 to 30, characterized in that the drying member (1 1) is a conveyor belt.

32. Device according to one of claims 26 to 31, characterized in that it comprises, downstream of the drying member (1 1), a means (15) for fluidizing the dry powder.

33. Device according to claim 32, characterized in that the means (1 5) for fluidizing the dry powder is a vibro-fluidizer.

34. Device according to claim 33, characterized in that the vibro-fuidiseur is provided with a heating means (14).

35. Device according to one of claims 32 to 34, characterized in that a means of transport (18) of the dry powder is disposed between the drying member (11) and the means (15) for fluidizing the dry powder.

36. Device according to one of claims 32 to 35, characterized in that a grinder (23) is arranged downstream of the fluidization means (15).

37. Device according to one of claims 26 to 36, characterized in that the atomization tower (7) comprises:

- A means (6) for supplying pressurized hot gas situated at the top of the atomization tower (7); - A means (2) of pressurized arrival of a liquid product containing viable microorganisms and opening onto a nozzle (3) located at the top of the atomization tower (7);

38. Device according to claim 37, characterized in that the atomization tower (7) further comprises a means (19) for evacuating the hot air loaded with particles of atomized product, located at the top of the tower d atomization (7).

39. Device according to claim 38, characterized in that the means (19) for discharging the hot gas loaded with particles of atomized product is connected to a means for recycling said particles, comprising a pipe (16) arriving at the top of the atomization tower (7) or on the drying member (11).

40. Device according to claim 39, characterized in that the means for recycling the particles of atomized product further comprises a cyclone effect device (8) at the top of which opens the means (19) for discharging the hot gas loaded with particles of atomized product and connected at its base to the pipe (16).

41. Device according to claim 40, characterized in that the cyclone effect device (8) has at its top a suction means (20).

42. Device according to claim 41, characterized in that the suction means (20) is a pipe connecting the fluidization means (15) to the top of a second cyclone effect device (9), itself connected by its base at the pipeline (16).

43. Device according to any one of claims 37 to 42, characterized in that the means (2) of arrival is pressure of the liquid medium containing viable microorganisms has a feed pump d).

44. Device according to any one of claims 37 to 43, characterized in that the means (2) of pressurized arrival of the liquid medium containing the viable microorganisms comprises a thermal regulation means (21).