WO2002022178A1

WO2002022178A1 - Method for destroying bacteria in a dry product

Info

Publication number: WO2002022178A1
Application number: PCT/FR2001/002809
Authority: WO
Inventors: Christian Claeys; Jean-Pierre Peyremorte
Original assignee: Lagarde; Les Cles Du Developpement
Priority date: 2000-09-12
Filing date: 2001-09-11
Publication date: 2002-03-21
Also published as: AU2001290001A1; FR2813797A1; FR2813797B1

Abstract

The invention concerns a method for bactericidal and insecticide treatment of a dry product in particulate form, said product containing organic substances and having a weight content of water less than 25 %. The invention is characterised in that it comprises steps which consist in: 1/ introducing said dry product into a chamber containing an oxygen-free inert atmosphere, and comprising preferably at least 50 % by volume of a bacteriostatic gas, and 2/ performing a heat treatment of said dry product in a reactor comprising: 2a/ heating the walls of said chamber to obtain a specific bactericidal treatment by evaporation of the water contained in said dry product, then 2b/ cooling the walls of said chamber while producing a relative movement of said dry product with respect to the walls of said chamber to obtain re-absorption into said product, of said water and if any, of said volatile organic substances condensed on said walls.

Description

PROCESS FOR DESTRUCTION OF BACTERIA FROM A DRY PRODUCT

The present invention relates to a process for debacterization and disinsection of a dry product in the form of particles. The present invention also relates to a dry product and a batch of dry product packaged in a package obtained by this process.

According to the present invention, the term “debacterization and disinsectization process” means a process making it possible to reduce the contamination and possible infection by any microorganism, such as bacteria, yeast, fungus or insect. This type of process is also designated under the generic name of "debacterization".

The term “dry product” is understood here to mean a solid product comprising a water content by weight of less than 25% (ratio of the weight of water to the total weight of the product). The dry product treated is a product in the form of particles. The term “particles” is understood here to mean a solid powdery product, in grains, in pieces or even in whole natural form, but the largest dimension of which is preferably less than 1 cm. The product will be in whole form, in particular in the case of certain dried fruits, dried vegetables, and plants which are then in whole leaves. For plants, the pieces may consist of crushed or cut leaves.

The treated product contains organic substances and can be a product for food use, but also a pharmaceutical, parapharmaceutical, phytosanitary, cosmetic and / or hygiene product. In dry products for food use, we cite more particularly by way of illustration and without limitation, aromatic plants, spices, dried fruits such as almonds, hazelnuts, nuts, dried vegetables such as beans and lentils, mushrooms or even cereals. For each product, in particular for food use, there is a quantity of total germs per gram of products not to be exceeded in order to be considered according to the standards, regulations or use in force, as "debacterized". In general, it is considered that a debacterization process leads to a reduction in the concentration of germs (germs / g) corresponding to a division by 10 ² , preferably by at least 10 ³ , or even at least 10 ⁵ and the number of germs. total per gram of dry, debacterized product must be less than 10 ⁶ , preferably 10 ⁵ . In general, a concentration of 3.10 ⁵ germs / g is acceptable.

There is known a method of debacterization and disinsection by heating by steam injection on dry products deposited in bulk on wire trays inside a cooker previously evacuated, the heating being carried out by steam injection inside said cooker. In this process, direct contact between the steam injected into the cooker and the dry product hydrates the product.

After said heat treatment, drying is carried out to remove the humidity provided by the steam. However, by direct contact with the vapor, said dry product loses organic substances by distillation. They are removed during drying. Thus, in the case of a dry food product, volatile aromatic compounds are lost during the treatment, which results in a loss of their organoletpic quality (Varoquaux P, 1997-CT-lnfo = 19: 6-8). In addition to the significant loss of aroma due to the distillation on heating and vaporization on drying which generally represents a loss of more than 20% of the starting aromatic substances. If necessary, partial oxidation of aromatic substances occurs due to air drying, an oxidation which is also a source of degradation in product quality. Another drawback of this process is that the quality of the dry product obtained is random and variable, in particular in terms of germ content, content of aromatic substances and color.

Other debacterization techniques are known which are costly techniques requiring significant operating security and are prohibited in many countries. This is in particular the ionizing beam technology which is furthermore subject to labeling conditions with compulsory indication on the label, of the nature of the ionizing treatment undergone to warn consumers of possible dangers, and technology by gas treatment such as ethylene oxide or methyl bromide. All the processes of the prior art mentioned above also present risks of recontamination at the end of the treatment despite the ultra clean conditions used to condition the debacterized products after treatment.

The problem underlying the present invention is therefore to provide a process allowing a heat decontamination treatment, in particular for herbal products, herbs and spices as well as any dry product for food or other use, without loss of aroma and without risk of recontamination after treatment.

More generally, the aim of the present invention is to provide a process for debacterization and disinsectization of dry product, coming within the framework of the regulations in force, not presenting the drawbacks of the above-mentioned existing processes, namely with:

- maintenance of the content of volatile organic substances at the origin of the properties of the product, whether organoleptic, in particular aromatic, for a food product or other for products having pharmaceutical or cosmetic properties, - absence of degradation or modification chemical of substances of interest contained in the product

- elimination of the risks of recontamination or development of residual bacteria after treatment,

- limitation of the oxidation of said organic products, - obtaining a product that is as homogeneous as possible in each batch treated, in particular in terms of content of volatile organic substances, in particular the substances involved in the properties and / or activity of said product dry treated, and with regard to the actual debacterization characteristics, - reduction in decontamination costs compared to previous processes. To do this, the present invention provides a method for debacterizing and disinsecting a dry product in the form of particles, said product comprising organic substances and having a water content by weight of less than 25%, characterized in that it comprises the stages in which:

1 / said dry product is introduced into an enclosure containing an inert gas atmosphere devoid of oxygen, and preferably comprising at least 50% by volume of a bacteriostatic gas, and

2 / a heat treatment of said dry product is carried out in a reactor comprising:

2a / heating the walls of said enclosure to obtain a given debacterization of said product by vaporization of the water contained in said dry product, then

2b / cooling the walls of said enclosure, while carrying out a relative movement of said product relative to the walls of said enclosure to obtain the reabsorption in said product of said water and of said volatile organic substances condensed on said walls.

The debacterization process according to the present invention is advantageous both in terms of preserving the characteristics of the treated product and in economic terms. In fact, in the first place, because the vaporization of the water contained in the product is sufficient to obtain the bactericidal effect, the product is preserved from any contact with an external thermal fluid, such as external water vapor, which reduces the risk of degradation and / or chemical modification of the organic substances contained in the product. Secondly, the water vapor condenses on the walls of the enclosure during cooling, and can thus be reabsorbed by the product, which has the effect of avoiding or reducing the loss of volatile organic substances entrained with l water contained in the product during its vaporization. Finally, there is no need for a subsequent step of eliminating humidity by drying, which reduces the cost of the process, but also reduces the risk of the development of residual thermophilic bacteria after debacterization.

“Relative movement of said product relative to the walls of the enclosure” is understood to mean a displacement of said product which is not in contact with the walls, so that it comes into contact with the wall and that consequently, the maximum of said product, preferably all of said product during treatment, comes into direct contact with said walls to be then subjected to said heat transfer by contact with said wall. At the heating stage, it is understood that the calorific intake achieved, that is to say the temperature at the heart of the product (T) which one seeks to achieve and the duration of treatment (t) during which maintains this temperature T (level), are determined as a function of the debacterization objective sought in a known manner by tests on a witness. The debacterization objective may depend in particular on the use for which the said product is intended.

During the heating step, the temperature of said enclosure is therefore raised until the necessary and sufficient temperature is obtained leading to the vaporization of the water contained in the product, and this temperature is maintained for the time required to obtain said debacterization at said temperature.

More particularly, as mentioned previously, the term "debacterization" means that the concentration of germs (germs / g) of the dry debacterized product must be less than 10 ⁶ , preferably less than 10 ⁵ - more particularly still the reduction in the concentration of germs corresponds to a division of the concentration of germs by at least 1000, preferably by at least 10 ⁵ .

In a particular embodiment, a heat treatment is carried out which makes it possible to obtain a debacterization value (DV) greater than 100, more particularly between 100 and 100,000, more particularly still between 1,000 and 10,000. The term "debacterization value (DV)" is understood here to mean a number of minutes during which the core temperature of the product is maintained at 70 ° C. It is indeed considered that beyond 60 ° C. bacteria are destroyed.

According to the method of the present invention, the heat input is provided by thermal transfer from the walls of said enclosure. The tightness of said enclosure allows the water and volatile organic substances initially contained in said product to be reabsorbed by said product during the cooling step.

In a particular embodiment of the method according to the invention, a heat treatment is carried out so as to reach a core temperature of the product of 60 to 135 ° C for 5 to 60 minutes.

More particularly, for the treatment of products for food use and in particular of aromatic plants, said temperature is between 90 and 120 ° C, preferably around 105 ° C for 10 to 30 minutes. In all cases, the pressure inside said enclosure is adapted, so as to obtain the temperature necessary for the vaporization of the water contained in said product during the heating step.

Said relative movement makes it possible to homogenize the product and the thermal transfer within the product and to accelerate the thermal transfer within the product during cooling. Thus, said relative movement promotes a homogeneous reabsorption by said dry product of water and organic substances condensed on the wall during cooling, which reduces the risk of excessive reabsorption of moisture in certain areas, the excess of humidity which can induce the development of residual thermophilic bacteria during cooling.

The cooling step is advantageously carried out under the conditions making it possible to rapidly reduce the temperature, in particular below 35 ° C., which has the effect of causing the condensation of the water vapor exuded from the product and the volatile organic substances which 'it contains, and also to avoid the possible development of residual thermophilic bacteria at intermediate temperatures during cooling. Preferably, the cooling step is carried out up to a temperature below 35 ° C, in particular up to an ambient temperature of 30 ° C, in a time less than or equal to the time necessary for the temperature rise of the product during of the heating stage. It is understood that this duration depends on the volume of said enclosure and on the quantity of product treated.

According to the present invention, by "oxygen-free atmosphere" means a volume oxygen content of less than 5%, preferably less than 1%. The term “inert atmosphere” means an inert gas such as nitrogen, argon or helium or a gas having no action other than bacteriostatic, that is to say which prevents the development of microorganisms without killing them. Mention may in particular be made, as bacteriostatic gas, of carbon dioxide CO ₂ or nitrous oxide N ₂ O.

According to the present invention, the inert atmosphere, that is to say the gaseous medium contained with the product in said enclosure, contributes to the heat transmission from the walls of said enclosure to the products during the heat treatment. The absence of oxygen prevents oxidation of the products. The use of a bacteriostatic gas prevents the possible development of thermophilic bacteria during cooling.

In an advantageous embodiment, said dry product is conditioned in an atmosphere saturated with CO ₂ .

Preferably for a continuous treatment, the heating and cooling stages are carried out separately, respectively in two separate compartments of the same reactor or in two different reactors.

In a first embodiment of the process of the invention, the dry product is introduced without packaging into a reactor, said enclosure then being the enclosure of the reactor. In this case, advantageously, after the cooling step of said heat treatment, the dry product leaving the reactor is conditioned in a package containing a so-called inert atmosphere devoid of oxygen and preferably comprising at least 50% by volume of a bacteriostatic gas. More preferably, a direct transfer is made from said enclosure in said packaging, that is to say without contact with the outside air. In a second embodiment, said dry product is introduced into said enclosure which is constituted by said product packaging, the dry product is treated in packaging and that is to say that the steps are carried out in which: 1) the packaging of said dry product in a sealed package containing a said inert atmosphere devoid of oxygen and preferably comprising at least 50% by volume of a bacteriostatic gas, and

2) introducing said product thus conditioned in a reactor and carrying out a heat treatment by heating and cooling the walls of said package in said reactor, said package retaining its shape and its seal under the conditions of said heat treatment.

By "sealed packaging" is meant a rigid or flexible container, the walls of which are made of a material which is non-porous to gases and liquids, in particular plastic, mineral material such as glass, metal or the like, which prevents contact between the contents of the container and the atmosphere inside the container with the outside atmosphere.

The gaseous medium contained in said packaging is useful for heat transfer and keeping the packaging in shape. The use of a bacteriostatic gas improves the storage conditions in said packaging.

To keep the shape of said packaging, it may be necessary to establish a back pressure inside said reactor to balance the internal pressure of said packaging. Said packaging can be of capacity adapted to the needs according to the destination of the product, said packaging being able to serve as storage or distribution means, which eliminates the risks of recontamination after treatment, and contributes to creating conditions of conservation of the specificities of said product after treatment, in particular by the possibility of distributing the product in the treatment packaging. To allow good debacterization and to ensure microbiological and physiological stability after treatment, it is preferable to control the moisture content.

The moisture content of the product intervenes on several levels: - On the one hand, we know for each product the maximum moisture content above which the product is considered to be preservable because its moisture content is insufficient to allow the development of bacterial flora, in general this maximum moisture content is 12% but can reach 25%. - On the other hand, during the heat treatment the water vapor exuded from the product increases the heat transfer between the walls of the enclosure or of the packaging where the heat input and said product is ensured, so that the debacterization is obtained at a temperature lower than that necessary when the water vapor is in insufficient quantity, or in the absence of water vapor.

- Finally, in the case of a gaseous CO ₂ atmosphere, water reacts with CO ₂ to give carbonic acid which has a high antioxidant and bacteriostatic effect.

More particularly, the humidity of said dry product is therefore adjusted to a weight content of water ranging from 5 to 25%, preferably from 9 to 12%, before its introduction into said enclosure, and in particular before packaging in said packaging.

A gas atmosphere saturated with CO ₂ used combined with a moisture content of the product of 9 to 12%, ensures a quality of the heat transfer, a bactericidal effect, as well as the maintenance of the organoleptic qualities of the product as explained below.

In a preferred embodiment of the method according to the invention, a relative movement of said dry product is carried out with respect to walls of said enclosure in particular with respect to the walls of said packaging, in order to homogenize the mechanical contact between said dry product and said walls of said enclosure or where appropriate of said packaging, during the cooling step and preferably during and after the heating step. Said relative movement during heating makes it possible to accelerate and homogenize the heat transfer and the temperature of the product in said enclosure. As a result, a more homogeneous product is obtained in each batch treated in terms of debacterization value and content of volatile organic substances, in particular the substances at the origin of the properties of said dry product, such as the organoleptic properties for a food product or the substances responsible or the activity of a pharmaceutical or cosmetic product.

It is understood that said relative movement can be obtained by stirring said product and / or said enclosure.

Advantageously, said dry product comprises volatile organic substances, preferably volatile aromatic compounds giving it organoleptic qualities, and these are reabsorbed at least partially in the product during the cooling step, the loss of said organic substance preferably being less than 20% by weight, more preferably less than 10% of the weight content of said substances in said product before said heat treatment. .

During the heating phase of the heat treatment, separation of volatile organic substances occurs, in particular by distillation. The term “volatile organic substance” is understood here to mean an organic substance capable of volatilizing during heating and / or of dissolving with the evaporated water vapor and / or of being entrained by said vapor. In the case of a dry food product, these substances include organoleptic substances such as fatty acids, and aromatic compounds. For each product having organoleptic properties, one can establish a spectrum of its organic substances which characterize the organoleptic qualities of the product. In plants, these substances are included in a distillate called essential oil of the plant.

After distillation of said volatile organic substances during the heat treatment phase, said substances condense on the walls of said enclosure or of said packaging during its cooling. The relative movement of the product relative to the walls of the enclosure or the packaging therefore promotes maximum conservation of said volatile organic substances inside said product by preventing the separation of said organic substances, in particular essential oils which distill and recondense on the walls during treatment, and by promoting the reabsorption of said substances to the interior of said product before and / or after their condensation on said walls.

The method according to the present invention therefore makes it possible, on the one hand, to avoid that the product loses too many substances during the heat treatment by significant dehydration, and on the other hand, that these volatile and / or soluble substances by diffusion in vapor. heaters are eliminated with them outside the treatment enclosure.

Advantageously, when the heat treatment is carried out by heating and cooling the reactor enclosure, in particular when introducing dry product without packaging into a said reactor enclosure according to said first embodiment, said gas constituting said inert atmosphere is injected in said reactor enclosure, preferably in said heating reactor, so that the pressure inside said enclosure is adapted to the heating temperature to be reached. For a treatment at 105-108 ° C, the pressure is advantageously 0.4 bar in said heating reactor, but can be reduced to 0.2 bar in said cooling reactor, where the desired temperature is 20 ° C.

More particularly, an industrial installation for continuous heat treatment is used, comprising from upstream to downstream:

1 / a heating reactor, and 2 / a cooling reactor.

The passage zone between the downstream end of said heating reactor and the upstream end of said cooling reactor advantageously comprises a rotary sluice valve making it possible to isolate them.

Similarly, advantageously, in said first embodiment in which the product is treated without packaging, said heating reactor is supplied with said product to be treated using a rotary valve and said treated product is discharged from said cooling reactor using a so-called same rotary valve through which it is directly transferred into a package.

Advantageously also, the displacement of the product in said reactors is ensured by mechanical means, for example, in the case of said first embodiment, by means of worms. The material is first brought into the heating reactor, which is for example in the form of a cylindrical enclosure. Then downstream of the heating reactor, the treated product enters the cooling reactor.

More particularly, the installation useful in said first embodiment of the method according to the present invention comprises the following characteristics:

- Said reactors comprise means for moving the product from upstream to downstream, in the case where the product is processed in bulk without packaging, in particular the reactors comprise helical longitudinal worm screws;

- Said heating reactor comprises a cylinder comprising a double-walled wall traversed by a hot fluid;

- a hot liquid fluid circulates if necessary in said longitudinal screw of said heating reactor; - Said cooling reactor comprises a cylinder comprising a double-walled wall traversed by a cold fluid;

- a cold fluid circulates if necessary in said longitudinal screw of said cooling reactor.

Thus the heat treatment of the material is carried out by contact on the walls of the cylinders if necessary and of the helical screws.

In order for this contact on the cylinder walls to be effective, it is preferable that:

- the volume of the bulk product in the cylinder is from 1/3 to 1/2 of the volume of the cylinder, and the helical screw is advantageous, because it drives the material by lifting it to project it on the walls of the cylinder. In said second embodiment of the invention, in which said product is treated with a package and said enclosure is constituted by said package, the relative movement of said dry product relative to said walls of the package can be obtained by shaking the container in which an empty head space of at least 1/8, preferably 1/5, more preferably 1/4 of the volume, has been arranged, thus allowing sufficient movement of said product inside said packaging.

More precisely in one embodiment, an empty space is maintained in said packaging, the filling of said packaging with said dry product being less than 95%, preferably from 3/4 to 4/5 by volume, and said packaging is agitated, preferably by rotation on itself.

Said packaging can be a rigid container or a container with flexible walls, the walls of which are maintained in shape by pressurizing the atmosphere internal to the packaging. The container used can be a jar, a box, a can of glass, metal or other rigid mineral or plastic material suitable for heat treatment with transfer of calories. It can also be a flexible material such as a plastic bag that an internal atmosphere under pressure keeps in shape. To carry out this type of packaging, a person skilled in the art knows suitable packaging machines.

In said second embodiment in which the product is treated in packaging, a reactor can be used in which the heat treatment is carried out by heating and then cooling the walls of the reactor as described above. However, in said second embodiment, preferably in the heat treatment step, said packaging is placed in an autoclave in which a calorific contribution is made by circulation of a thermal fluid or immersion and / or circulation of vapor, preferably by injecting steam into said autoclave, and said cooling is carried out by running cold water on the walls of said packaging.

In another alternative embodiment of said second embodiment, the heat treatment is carried out by creating agitation molecular treatment of said package using microwave or high frequency radiation.

As mentioned above, the method according to the invention is particularly advantageous when said dry product comprises volatile aromatic compounds which give it organoleptic qualities. The loss of organic substances characteristic of a property, in particular organoleptic, can have a double cause:

M the substance can be degraded or modified chemically, in particular by oxidation, u the substance initially distilled during the heat treatment, can be incompletely reabsorbed by the dry product later.

The method according to the invention according to which a heat treatment is carried out in an inert atmosphere in a sealed enclosure with stirring, and with a certain moisture content of the dry product treated, makes it possible to obtain an almost complete conservation of the organic substances, in particular organoleptic substances, such as aromatic compounds, from food products in the processed product.

The method according to the invention is also particularly advantageous because of its simplicity and its low cost of implementation. The present invention also relates to a new dry product which can be obtained by the debacterization and disinsectisation process according to the invention. Said dry products obtained by the process according to the invention have a weight content of volatile organic substances at least 10% higher than the content of the same volatile organic substances in the same debacterized product before packaging in a said inert atmosphere, in particular by heat treatment. Here we mean by

"same product" means a product with the same physical configuration such as powder, grain, lump, the same particle size and the same amount of germs. More particularly, a dry debacterized product according to the present invention can be characterized in that it has volatile active organic or organoleptic substances, preferably aromatic compounds, and its loss in said substances is less than 20% by weight, preferably less than 10% of the content of said substances in the starting product before said treatment.

The present invention also relates to a batch of dry products packaged according to the process of the invention, these batches being characterized by a greater homogeneity of their characteristics in terms of quantities of total germs and in content of volatile organic substances, in particular in aromatic substances.

Preferably the dry product obtained has a humidity of 5 to 25%, more preferably from 9% to 12% and its concentration in total germs is less than 10 ⁶ germs / g, preferably less than 10 ⁵ germs / g.

Other characteristics and advantages of the present invention will become apparent in the light of the detailed description of the embodiments which follows. Figure 1 shows a diagram of the rotary autoclave used.

FIG. 2 represents the graph of the temperature profile in the autoclave as a function of time.

Figures 3 to 6 show organoleptic profiles of thyme treated in different ways obtained with an electronic nose. FIG. 7 represents a schematic sectional view of an installation according to said first embodiment of the invention.

EXAMPLE 1:

Various products were packaged in waterproof 800 ml glass jars partially filled with products under an atmosphere saturated with CO ₂ . A heat treatment was carried out in a rotary autoclave 1 used in the existing methods of canned sterilization of vegetables in rigid containers as shown in FIG. 1 in which the jars (not shown) are placed in a basket 2 with rigid walls at skeleton, said basket 2 being subjected to an axial rotation in the heat treatment and cooling phase. The jars are stored and placed side by side on racks inside the basket 2. The axial rotation of the basket generates a rotational movement of the jars on themselves according to a head-to-tail movement.

The rotary canned autoclave used, brand "LAGARDE ®", operated with steam injection 3 for heat treatment and cooling with cold water 4a, 4b with permanent stirring during heat treatment and the cooling phase .

The products treated were as follows:

- whole or ground basil leaves

- ground cinnamon - coriander in seed or ground

- cumin in seed

- ground turmeric

- different spice mixes such as curry, rouille, Rabelais spices, Colombo spices, - ginger root flakes

- ground garlic

- cloves

- whole leaves of Provence herbs

- cut bay leaves (pieces of about 1cm ² ) - ground nutmeg

- onion in strips or strips (about 1cm long and a few mm wide) or powder

- whole oregano

- whole leaf parsley - crushed sweet pepper or powder

- various types of peppercorns or ground pepper

- whole or ground rosemary leaves

- Sesame seed

- extra gray thyme whole leaves. The moisture content of the starting dry product was varied. The filling rate of the container was also varied. The temperature scales at the heart of the product and the duration of establishment (plateau) of the said temperature at the heart of the product, were established according to the values indicated in the literature, that is to say approximately 105 ° C. for 10 minutes corresponding to a debacterization value of 8,000 to 10,000 for the treated products, except for garlic for which the temperature was 75 ° C for 25 minutes. For fatty products, there is indeed a solidification if the treatment temperature is excessive. These core temperatures are recorded using an ELLAB® brand device. To obtain this temperature profile, a temperature profile is applied to the interior of the autoclave, the bearing of which is slightly higher than the desired core temperature, as shown in FIG. 2, approximately 170 ° C.

The controls and the products treated in jars were stored for one month at room temperature, protected from light.

Comparative analyzes were carried out on the controls and treated products.

1.1. - Debacterization

These were microbiological analyzes allowing the measurement of the number of germs (germs / gr) of microorganisms considered to be characteristic.

The essential oil contents (ml / 100 g) were also measured in the control and the treated product.

At the ready analysis error, a total conservation of the essential oil content was obtained for products having been debacterized with a total germ count less than 10 ⁵ and more particularly from 10 ² to 10 ⁵ germs / g in the following conditions:

- the free space in the container was 10 to 25%, preferably around 15%

- the agitation of the products was neither too slow nor too fast to avoid in the latter case a centrifugation of the substances, namely from 5 to 15 rpm, preferably 8 rpm

- the moisture content of the treated product was about 9 to about 12%. The moisture content of the dry product was adjusted before packaging, either by adding and mixing the product with water, or by evaporating part of the water.

If the moisture content is insufficient, the debacterization treatment is difficult to carry out and there is a loss of organic substances, in particular aromatic compounds. Indeed, if the product is not wet enough, it reabsorbs the organic substances which have been distilled and condensed on the walls less well during cooling.

In known manner, the temperature to be applied and the duration of application of this temperature had to take into account not only the nature of the product treated but also its particle size (particle size) to optimize the heat treatment scales.

By way of illustration, Tables 1 to 5 below report the analyzes carried out on a mixture of ground spices, ground basil, ground peppercorns, whole herbs of Provence and ground nutmeg under the conditions optimum procedures described above (atmosphere saturated with CO ₂ , filling 7/8 of the glass jar, temperature at the heart of the product 105 ° C for 10 minutes).

TABLE 1: MIX OF GROUND SPICES

TABLE 2: GROUND BASIL

TABLE 3 - GRAY PEPPERS

TABLE 4: HERBS FROM PROVENCE

TABLE 5: GROUND MUSCADE

1.2. Aromatic analysis

The various analyzes demonstrate an almost total conservation of the aromatic and organoleptic qualities of the products treated.

In tables 1 to 5, the conservation of the content of essential oils is reported.

These positive results were confirmed by analysis with a device called an "electronic nose" which determines the organoleptic profiles characteristic of a product.

FIG. 3 represents the organoleptic profile of an untreated control product (whole leaf thyme).

FIG. 4 represents the organoleptic profile of the same product treated according to the method of the invention in an atmosphere of CO ₂ , in a non-porous container.

FIG. 5 represents the same product treated in air and in a non-porous container.

FIG. 6 represents the same product treated in a CO ₂ atmosphere but in a porous container.

In FIGS. 3 to 6, the lines starting from the center of the decagons and bearing the references T30 / 1, TA2, T40 / 1, P10 / 1, P10 / 2, P40 / 1, T70 / 2, PA2, P30 / 1, P40 / 2, P30 / 2, T40 / 1 represent the different reference olfactory values of the measuring device used in the composition of the aromatic bouquet of the treated product (thyme). For each olfactory value, a variation compared to the reference value of the device is expressed by the distance from the end of the ray relative to the center graduated from 0 to 1. The comparison of the different organoleptic profiles represented in Figures 3 to 6 demonstrates that a product treated according to the operating conditions of the method according to the present invention (Figure 4) in a sealed enclosure made of a non-porous material has the greatest similarity with the profile of the control product (Figure 3). A gas chromatographic analysis reveals by comparison of the chromatograms that the analyzed samples (controls and treated samples) have identical molecular compositions. The treated products have higher contents of the different aromatic volatile fractions than the control samples when treatment is carried out in a CO ₂ atmosphere. This improvement is explained by the fact that for the samples treated during the treatment, certain molecules are deoxidized and appear in the volatile fraction, while in oxidized form in the control sample they do not appear.

EXAMPLE 2:

FIG. 7 represents a schematic sectional view of an installation of a first embodiment of the invention in which the treatment of product to be treated in bulk is carried out without packaging in a sealed reactor enclosure, comprising a heating reactor 1 and a cooling reactor 2. At an upstream end 1 ι _, the heating reactor 1 is supplied with said product via a hopper 1 ₂ and a metering lock such as a rotary valve 1 ₃ comprising a plied with blades rotating in a cylinder and thus making it possible to isolate the interior of said enclosure from the outside air and promoting the evacuation of air from the reactor enclosure to the outside. The heating reactor comprises means for injecting inert gas 5 upstream of said reactor. When the desired temperature inside the heating reactor is 105-108 ° C, inert gas, in particular CO ₂ , is injected so as to reach a pressure of approximately 0.4 bar. The heating reactor 1 and the cooling reactor 2 are constituted by cylinders comprising a double jacket 1, 2. In the internal space of this double envelope circulates a heated fluid for the heating reactor, so as to obtain a desired temperature inside the reactor and therefore at the heart of the product. Likewise, the cooling reactor 2 is also essentially cylindrical in shape with a double jacket inside which a fluid such as water circulating around 20 ° C. circulates. The pressure inside the cooling reactor 2 is adjusted to about 0.2 bar. In one embodiment (not shown), the two reactors comprise means for moving material from upstream to downstream consisting of a longitudinal helical screw whose diameter occupies substantially the interior volume of the cylinder constituting the reactors and whose inclination of the blade drives the material by lifting it to project it onto the walls of the cylinder, so that the heating of the product in the reactor is obtained by contact on the walls of the cylinder and of the helical screw, insofar as the latter is advantageously traversed by a said fluid inside. At the downstream end 2 ₂ of said cooling reactor, the product is poured directly into said packages 4 after passage through a rotary valve 2 ₃ which insulates the cooling compartment 2 from said package 4. The speed of displacement of the product in the reactors is adjusted so that the product is heated for a desired time inside said heating reactor according to a particular embodiment for 10 to 30 min at approximately 105 ° C. The upstream end or inlet 2-j of the cooling reactor is located below the outlet 1 of the heating reactor and the two downstream ends 1 ₂ and upstream 2-ι are separated by a separation lock consisting of a rotary valve 3 The temperature in the heating reactor 1 and at the outlet from the cooling reactor 2 is controlled by measuring means 6.

Claims

1. A process for debacterization and disinsection of a dry product in the form of particles, said product containing organic substances and having a water content by weight of less than 25%, characterized in that it comprises the steps in which:

1 / said dry product is introduced into an enclosure containing an inert atmosphere devoid of oxygen, and preferably comprising at least 50% by volume of a bacteriostatic gas, and

2a / heating the walls of said enclosure to obtain a given debacterization by vaporization of the water contained in said dry product, then

2b / cooling the walls of said enclosure, while carrying out a relative movement of said dry product with respect to the walls of said enclosure to obtain the reabsorption in said product, of said water and, where appropriate, of said volatile organic substances condensed on said walls .

2. Method according to claim 1, characterized in that a relative movement of said dry product is carried out with respect to the walls of said enclosure, in order to homogenize the mechanical contact between said dry product and said walls of said enclosure, during the 'cooling step and during the heating step.

3. Method according to claim 1 or 2, characterized in that the heating and cooling steps are carried out separately, respectively in two separate compartments of the same reactor or in two different reactors.

4. Method according to claim 1 to 3, characterized in that said dry product without packaging in an enclosure which is the enclosure of a said reactor and after the cooling step, conditioning at the outlet of said enclosure d 'said reactor the dry product in a package containing a said inert atmosphere devoid of oxygen and preferably comprising at least 50% by volume of a bacteriostatic gas, preferably by direct transfer from said enclosure, without contact with air outside.

5. A method for debacterization and disinsectization of a dry product according to claim 1 to 3, characterized in that said enclosure is constituted by a packaging of said product and it comprises the steps in which:

1) the packaging of said dry product is carried out in a sealed package containing a so-called inert atmosphere devoid of oxygen and preferably comprising at least 50% by volume of a bacteriostatic gas, and 2) the said product thus conditioned is introduced into a reactor and performing said heat treatment by heating and cooling the walls of said package in said reactor, said package retaining its shape and its seal under the conditions of said heat treatment.

6. Method according to one of claims 1 to 5, characterized in that the humidity of said dry product is adjusted to a weight content of water ranging from

5 to 25%, preferably 9 to 12%, before its introduction into said enclosure and in particular before packaging in said packaging, and said atmosphere is saturated with CO2.

7. Method according to one of claims 1 to 6, characterized in that said reactor consists of a cylindrical enclosure preferably comprising means for moving said product, and more preferably comprising a double-walled wall traversed by a fluid allowing said heat treatment.

8. Method according to claim 7, characterized in that said reactor comprises from upstream to downstream a heating reactor (1) and a reactor cooling (2), said reactors (1, 2) comprising means for moving the product from upstream to downstream, preferably said heating reactor comprising a cylinder comprising a jacketed wall traversed by a hot fluid, and said reactor cooling (2) comprising a cylinder with a double-walled wall traversed by a cold fluid.

9. Method according to claim 8, characterized in that said product is treated in bulk without packaging and said reactors each comprise a helical screw with longitudinal end, and preferably said fluids circulate in said longitudinal screws of said reactor.

10. Method according to one of claims 4, and 6 to 9, characterized in that said gas constituting said inert atmosphere is injected into said reactor enclosure, preferably into said heating reactor, so that the pressure inside said enclosure is adapted to the heating temperature to be reached for said heat treatment.

11. Method according to one of claims 4 and 6 to 10, characterized in that said reactor enclosure is filled with said dry bulk product without packaging in a proportion of 1/3 to 1/2 by volume.

12. Method according to one of claims 5 to 8, characterized in that said product is treated in a package and the filling of said package with said dry product is less than 95%, preferably from 3/4 to 4/5 in volume, and said package is agitated, preferably by rotation on itself.

13. Method according to one of claims 5 to 8 and 12, characterized in that said product is treated in a package and in step 2, said package is placed in an autoclave in which a calorific contribution is made by circulation d 'A thermal fluid or immersion and / or circulation of steam, preferably by injecting steam into said autoclave, and said cooling is carried out by running cold water on the walls of said packaging.

14. Method according to one of claims 5 to 8 and 12, characterized in that the heat treatment is carried out by treatment of said packaging using microwave or high frequency radiation.

15. Method according to one of claims 1 to 14, characterized in that a heat treatment is carried out so as to reach a core temperature of said product from 60 to 135 ° C for 5 to 60 minutes.

16. The method of claim 15, characterized in that said temperature is about 105 ° C for 10 to 30 minutes.

17. Method according to one of claims 1 to 16, characterized in that said dry product comprises volatile organic substances, preferably volatile aromatic compounds giving it organoleptic qualities, and these are reabsorbed at least partially in the produced during the cooling step, the loss of said organic substance being preferably less than 20% by weight, more preferably less than 10% of the weight content of said organic substance in said product before said heat treatment.

18. Dry debacterized product obtainable by the process according to one of claims 1 to 17.

19. Dry debacterized product according to claim 18, characterized in that it comprises volatile active organic or organoleptic substances, preferably aromatic compounds, and the loss of said organic substances is less than 20% by weight, preferably less than 10% of the content of said substances in said product before said heat treatment.

20. Dry product according to one of claims 18 and 19, characterized in that it is a powdered product, in grains, in pieces or whole, for food, pharmaceutical, parapharmaceutical, phytosanitary, cosmetic or hygienic use. .

21. Dry product according to claim 20, characterized in that it is an aromatic plant, a spice of a fruit or a dry vegetable.

22. Dry product according to one of claims 18 to 21, characterized in that the number of total germs per gram of dry debacterized product is less than 10 ⁶ , preferably less than 10 ⁵ and its moisture content by weight is 5 at 25%, preferably 9 to 12%.

23. Lot of dry product, packaged in a package in which it has been debacterized according to one of claims 1 to 17.