Patent Description:
The present invention is suitable for handling different types of liquids, including liquids containing gases, solids and/or liquid substances, such as mixtures, slurries, gels, etc. The method according to the present invention can be applied to substantially any material or mixture of materials, in a liquid state and having viscosities in a wide range of values, capable of flowing.

As it is known, in many industrial sectors, such as food, cosmetics, pharmaceuticals and waste disposal, there is the need to subject different types of liquids to treatments capable of reducing the microbial load present in them.

For example, food liquids intended for human and animal consumption, such as beverages (e.g. water, milk, fruit juices, wine), oil, canned food, animal feed, etc., require treatments capable of preventing the proliferation of contaminating microorganisms, which find a favourable environment for their growth in these products. Uncontrolled proliferation of microorganisms can compromise the safety and shelf life of products.

Similarly, the need to obtain liquids with a controlled microbial load is also felt in the processes for the production of cosmetic products (creams, lotions, etc.. ), pharmaceutical products (active ingredients, pharmaceutical intermediates, etc.. ) or in the processes for the treatment of liquid waste such as sewage produced by civil settlements, wastewater from industrial processes, sewage sludge, biological liquid waste (blood, urine, etc..

The control of the microbial load in the aforesaid liquids meets the need to ensure the safety of their consumers or users and the safety of the working environments in which they are used.

Known methods in the state of the art for reducing the microbial load of a liquid include, for example, sterilization, pasteurization, ozonation, microfiltration treatments, and others. These treatments, although effective, nevertheless have several disadvantages, such as high energy consumption, particularly in the case of methods involving heat treatment of liquids, the use of chemicals, the use of bulky equipment or equipment operating with high pressure fluids (e.g. boilers for the production of steam), the use of expensive filtration membranes, etc..

In the state of the art, methods for reducing the microbial load of food products are also known, which involve treating these products by irradiation with electromagnetic radiation.

<CIT> describes, for example, a treatment for sanitising the rind of Gorgonzola PDO cheese in which the rind is subjected to a series of successive heat treatments in which: the first heat treatment is carried out at low temperature (<NUM>-<NUM>) for a duration of <NUM> - <NUM> hours in a forced air cooling tunnel; the second heat treatment is carried out at high temperature (<NUM>-<NUM>) by irradiation through infrared radiation for a duration of <NUM> - <NUM> seconds; the third heat treatment is carried out at low temperature (<NUM>-<NUM>) for a duration of <NUM> - <NUM> hours in a forced air cooling tunnel. This treatment method is described for exclusive use in cheese sanitization; the overall duration of the treatments is rather long, about <NUM>-<NUM> hours.

A method for reducing the microbial load applied to sausages is described in <CIT>. The method involves a low temperature heat treatment (<NUM>-<NUM>) followed by a high temperature heat treatment (<NUM>-<NUM>) performed through irradiation with infrared radiation and by a second low temperature heat treatment (<NUM>-<NUM>).

A method for reducing the microbial load using electromagnetic radiations applied to eggs is described in <CIT>. The method includes a first heat treatment at a temperature within the range <NUM>-<NUM> followed by a second heat treatment at a temperature within the range <NUM>-<NUM> and by a cooling phase at a temperature within the range <NUM>-<NUM>. The two heat treatment steps are performed through irradiation with infrared radiation having two different wavelengths (λ = <NUM>-<NUM> micrometers for the first treatment and λ = <NUM>-<NUM> micrometers for the second treatment).

<CIT> refers to a process for the transfer of electromagnetic energy in colloidal, micellar or molecular media, characterized in that the colloidal, micellar or molecular medium to be treated is brought to the treatment temperature, away from air, then subjected to irradiation using electromagnetic waves during the flow of this medium and by the fact that the colloidal, micellar or molecular medium to be treated is maintained under pressure for the duration of this irradiation, so that the Brownian motion generated within this medium is activated and the cross section of the molecules and micellar granules is increased.

<CIT> discloses a method and an apparatus for the irradiative treatment of beverages to sterilize or pasteurize them, in which the beverage is pumped through the system out of contact with the air. The entering beverage is heat exchanged against the exiting beverage, and is then subjected to ultra-violet irradiation, and further heat exchange against the exiting beverage.

The known methods described above, although they effectively reduce the microbial load and limit energy consumption compared to the methods used in the food sector (e.g. sterilization and pasteurization), have the disadvantage of being usable only in the case of substantially solid products, such as sausages, cheese and eggs.

In view of the aforementioned state of the art, the Applicant has set itself the primary objective of providing a method and apparatus for reducing the microbial load in a liquid, which overcome at least in part the drawbacks of the methods known in the state of the art.

In particular, a specific object of the present invention is to provide a method and an apparatus for reducing the microbial load in a liquid that are quick and easy to carry out and characterized by low energy consumption.

A second object of the present invention is to provide a method and an apparatus for reducing the microbial load in a liquid that are applicable to liquids having a variety of chemical, physical and/or rheological characteristics.

A third object of the present invention is to provide a method and an apparatus that allow to reduce the microbial load in a liquid without significantly altering the other characteristics of the liquid being treated; for example, in the case of food liquids, without significantly altering the organoleptic qualities.

A further object of the present invention is to provide a method and an apparatus for reducing the microbial load in a liquid, which can be readily integrated into existing manufacturing processes that produce or employ such liquids.

A further object of the present invention is to provide a method and an apparatus for reducing the microbial load in a liquid that can be adapted for use in treating small and large volumes of liquids.

The Applicant has found that the aforementioned and other objects, which will be more fully explained in the description below, can be achieved by exposing a liquid whose microbial load is to be reduced to infrared radiation (IR) emitted according to a specific irradiation sequence in which periods of exposure of the liquid to infrared radiation (heating phases) alternate with periods in which the liquid is not exposed - periods of non-exposure - to the aforesaid radiation (cooling phases).

It has been surprisingly found, in fact, that the aforesaid irradiation sequence is able to devitalize the microorganisms present in the liquid, thus reducing the microbial load in a simple, rapid way and with a very low energy consumption.

Without referring to any particular theory, it is believed that the exposure of the liquid to infrared radiation induces a sudden local heating of the liquid, which is followed by an equally sudden cooling of the same when the exposure to infrared radiation ceases. An irradiation sequence comprising at least two heating phases spaced out with a cooling phase thus generates a thermal shock in the body of the liquid, which devitalizes the microorganisms present in it; since the energy transmitted to the liquid in the form of radiation is relatively low and the duration of the treatment is relatively short, the irradiation does not significantly modify the other characteristics of the liquid, such as chemical composition, rheological characteristics and organoleptic properties.

It has also been observed that a relatively small number (less than <NUM>) of short periods of exposure to IR radiation (of up to <NUM> seconds each) are sufficient to reduce the microbial load in treated liquids to the levels required in most industrial applications, particularly in the case of the treatment of food and cosmetic liquids. The treatment is therefore effective, quick and can be used to treat a wide variety of different liquids.

In accordance with the present invention, the irradiation of the liquid with infrared radiation is carried out while the liquid is made to flow inside a tubular conduit, which is structured to be transversely crossed by the infrared radiation emitted by a plurality of IR sources placed in the vicinity thereof and suitably spaced between them along the direction of flow of the liquid in the conduit.

By using IR sources extending for a suitable length measured along the direction of flow of the liquid in the conduit, and by suitably spacing each IR source from the next one, it is possible to subject the liquid to a desired irradiation sequence, exposing the liquid during its path in the tubular conduit to alternating heating and cooling phases, both of predetermined duration for a given velocity of flow of the liquid. For a given configuration of the apparatus (arrangement, length and reciprocal distance of the sources), it is also possible to adjust the exposure and non-exposure times of the liquid to the IR radiation (i.e. the duration of the heating and cooling phases) by varying the velocity of flow of the liquid in the conduit.

Since no high-temperature heat treatments are performed and no chemical additives are used, the method for reducing the microbial load with infrared radiation described herein is characterized by low energy consumption and reduced environmental impact. The method based on irradiation with infrared radiation also allows a homogeneous treatment of the liquid, thus ensuring the reproducibility of the obtainable effect of reduction of the microbial load.

The method and the apparatus, moreover, have a high flexibility of use, being able to be used for the treatment of liquids having also very different chemical composition and rheological characteristics.

A further advantage of the present invention lies in the fact that the treatment method is carried out by means of an apparatus comprising one or more modular elements (treatment modules), each of which is capable of treating a certain mass of liquid in the unit of time. Therefore, by varying the number of treatment modules of the apparatus and by connecting them in parallel or in series, it is possible to treat masses of liquid that may vary greatly based on the needs of the user.

Furthermore, the method and the apparatus according to the present invention can be easily integrated into existing industrial plants by connecting them, for example, to plants for preparing and/or packaging the liquids of interest, even in confined spaces taking into consideration the small overall dimensions of the treatment modules.

In accordance with a first aspect, therefore, the present invention relates to a method for reducing the microbial load of a liquid comprising the phases:.

In accordance with a second aspect, the present invention relates to an apparatus (<NUM>) for carrying out the aforesaid method for reducing the microbial load in a liquid comprising at least one treatment module (<NUM>) comprising:.

Further characteristics of the process according to the present invention are defined in the dependent claims <NUM> - <NUM>.

For the purposes of the present invention, the term infrared radiation means electromagnetic radiation having a wavelength comprised within the range <NUM> - <NUM>,<NUM> micrometers.

The features and advantages of the process according to the present invention will be more apparent from the following description referring to the appended figures, wherein:.

The following description and the following examples of embodiment are provided for the sole purpose of illustrating the present invention and are not to be understood in a sense limiting the scope of protection defined by the appended claims.

With reference to <FIG>, a treatment module <NUM> according to the invention comprises at least a tubular conduit <NUM>, the inner surface of which defines a flow cavity into which the liquid to be treated can flow. The tubular conduit <NUM> comprises an inlet opening <NUM> and an outlet opening <NUM> defined by the inner surface of the conduit <NUM>, through which the liquid <NUM> enters and exits.

At least a portion <NUM> of the conduit <NUM> is transparent to infrared radiation; in particular, the aforesaid portion <NUM> is transparent to at least infrared radiation having a wavelength within the range <NUM> - <NUM> micrometers, preferably within the range <NUM> - <NUM> micrometers, more preferably within the range <NUM> - <NUM> micrometers.

For the purposes of the present invention, the expression "portion transparent to infrared radiation" means that said portion allows the passage of the infrared radiation having a wavelength and intensity such as to allow the reduction of the bacterial load of the liquid flowing in the tubular conduit so as to achieve the microbial load reduction effect illustrated in the present description.

The portion <NUM> that is transparent to infrared radiation can be made from materials known to the expert in the field, such as quartz, Vycor®, glass ceramic.

In a preferred embodiment, the aforesaid material is quartz. Preferably, quartz has one or more of the following characteristics:.

The material known by the trade name Vycor®, manufactured by Corning Glass Works, is a high-temperature, silica glass having a very high thermal shock resistance, consisting of about <NUM>% silica and about <NUM>% boron trioxide.

In a preferred embodiment, the entire tubular conduit <NUM> is made of a material transparent to infrared radiation, such as the aforesaid quartz.

The profile of the tubular conduit <NUM> may be substantially of any shape, e.g. circular, square, rectangular, etc. Preferably, the tubular conduit <NUM> has a circular profile.

The treatment module <NUM> comprises three sources 16a, 16b, 16c of infrared radiation located in the vicinity of said portion <NUM> transparent to infrared radiation, external to the tubular conduit <NUM>.

The sources 16a, 16b, 16c are positioned along a direction parallel to the longitudinal axis of said tubular conduit <NUM>, at a distance r (greater than zero) from each other. The distance r is within the range <NUM> - <NUM>, preferably within the range <NUM> - <NUM>.

The sources 16a, 16b, 16c may be separated by the same distance r from each other. The sources 16a, 16b, 16c, however, may also be positioned at different distances r from each other.

In an embodiment, the module <NUM> comprises a succession of n sources 16a, 16b, 16c of infrared radiation arranged along a direction parallel to the longitudinal axis, each spaced from the next one by a distance r, where n is an integer within the range <NUM>-<NUM>, preferably within the range <NUM>-<NUM>. According to the invention, n equals <NUM>.

For the purposes of the present invention, infrared radiation sources of the type known in the state of the art and commercially available may be used. Preferably, the infrared radiation sources comprise a filament source.

Preferably, the power of each source of infrared radiation is within the range <NUM>,<NUM> - <NUM> W.

Preferably, in the various embodiments of the present invention, the sources 16a, 16b, 16c develop predominantly linearly in a direction parallel to the longitudinal axis of said tubular conduit <NUM>.

According to the invention, each IR source 16a, 16b, 16c extends linearly in a direction parallel to the longitudinal axis of the tubular conduit <NUM>, for a length L, L', L", measured parallel to the longitudinal axis of said tubular conduit <NUM>, within the range <NUM> - <NUM>, preferably within the range <NUM> - <NUM>, even more preferably within the range <NUM> - <NUM>. Each source may have a length L, L', L" equal to or different from the length of the other sources present.

In an embodiment, the treatment module is housed within a refractory material support, which completely encloses it (not shown in the figure).

Each source 16a, 16b, 16c is configured to transmit an infrared radiation <NUM> preferably having a wavelength within the range <NUM> - <NUM> micrometers, more preferably within the range <NUM> - <NUM> micrometers, even more preferably within the range <NUM> - <NUM> micrometers, to the liquid <NUM> flowing inside the tubular conduit <NUM>.

In carrying out the treatment method, the liquid <NUM> is made to flow into the conduit <NUM>, for example in the direction indicated by the arrow F, at a desired flow velocity v, by means of pumping means, either by push or suction (not shown in the figure), or by gravitational fall. At the source 16a, the mass of the liquid <NUM> is exposed to the infrared radiation <NUM> emitted by said source.

The emission intensity of the radiation from each source 16a, 16b and 16c is preferably adjusted such that the radiation <NUM> penetrates the mass of the liquid <NUM> until it impacts against the wall of the tubular conduit <NUM> opposite the portion <NUM> transparent to the infrared radiation. This can be done by adjusting the emission power of the source, taking into account the density of the treated liquid. Typically, the applied power required for this purpose decreases as the density of the liquid to be treated increases.

The exposure of said mass of the liquid <NUM> to the infrared radiation of the source 16a lasts until said mass has travelled the entire length L of extension of the source 16a (heating phase). In the section of length r separating the source 16a from the source 16b, the aforesaid mass of the liquid <NUM> is not exposed to any infrared radiation, thus the cooling of the liquid <NUM> is carried out (cooling phase).

Similarly to what happens at the source 16a, the mass of the liquid <NUM> is subjected to a second phase of exposure to IR radiation at the source 16b. The duration of this second heating phase is determined by the length extension L' of the source 16b along the flow direction F and by the flow velocity v of the liquid <NUM>. This second phase of heating the liquid is followed by a second phase of cooling the liquid at the section of conduit <NUM> of length r, which separates the source 16b from the source 16c, in which the liquid <NUM> is not exposed to the infrared radiation.

In the embodiment exemplified in <FIG>, in its path across the conduit <NUM>, the liquid <NUM> is treated with the infrared radiation at the source 16c (optional) in a manner similar to that described for the sources 16a and 16b. At the end of this third heating phase, the liquid <NUM> outflows from the opening <NUM> of the tubular conduit <NUM>.

The liquid <NUM> exiting the tubular conduit <NUM> may be directed to other processes or accumulated in storage tanks. For example, the treated liquid can be stored at room temperature or in a refrigerated environment (e.g. <NUM> - <NUM>), or passed through a heat exchanger or blast chiller.

According to the invention, the liquid flowing inside the tubular conduit is treated according to an irradiation sequence comprising:.

wherein the aforesaid phases i), ii) and iii) are interspersed with periods of non-exposure of the liquid to infrared radiation of duration within the range <NUM> - <NUM>, which are cooling phases.

The liquid fed into the tubular conduit inlet is preferably at a temperature within the range <NUM> - <NUM>.

The treatment of the liquid in accordance with the method according to the present invention may advantageously be carried out in a tubular conduit <NUM> having a flow cavity with a diameter within the range <NUM> - <NUM>, preferably within the range <NUM> - <NUM>.

Preferably, the tubular conduit <NUM> has an overall length within the range <NUM> - <NUM>, preferably within the range <NUM> - <NUM>. The desired irradiation sequence can also be achieved by connecting two or more treatment modules in series.

The tubular conduit is preferably linear in shape, but may also have a curved shape (e.g. coil).

The flow of the liquid can be horizontal, vertical or inclined.

Preferably, the volumetric flow rate of the liquid flowing in the tubular conduit is within the range <NUM><NUM>/min - <NUM>/min, more preferably within the range <NUM><NUM>/min - <NUM>/min.

The aforesaid dimensions of the tubular conduit and the volumetric flow rate values allow to carry out the treatment for abating the microbial load in the liquid, maximizing the energy efficiency.

Since it is preferable not to use tubular conduits whose diameter sizes exceed those of the aforesaid ranges, if it is desired to carry out the treatment of relatively large masses of liquid, it is preferable to use a plurality of treatment modules of the type described above, connected together in parallel, as shown schematically in <FIG>.

In <FIG>, an embodiment of an apparatus <NUM> comprising three treatment modules 1a, 1b, 1c connected to each other in parallel is illustrated. A flow <NUM> of a liquid to be treated is fed to the apparatus <NUM>, which is divided into three aliquots <NUM>, <NUM>, <NUM>, each of which is sent to one of the treatment modules 1a, 1b, 1c. The treated liquids <NUM>, <NUM>, <NUM> exiting from the treatment modules 1a, 1b, 1c, respectively, are merged into a single final flow <NUM>, which is fed to possible further thermal treatments or to storage.

The aforesaid liquids are moved in the apparatus <NUM> by, for example, pumping systems not shown in <FIG>.

The use of treatment modules assembled in parallel in a single apparatus offers the advantage of making the method according to the present invention easily sizable according to the volumes of liquid to be treated. As mentioned above, the treatment modules may also be connected in series, for example in the event that it is desired to treat the liquid along a flow path greater than that defined by a single treatment module.

For example, the apparatus may comprise a number of treatment modules connected in parallel within the range <NUM>-<NUM>, preferably within the range <NUM>-<NUM>, more preferably within the range <NUM>-<NUM>.

The method and the apparatus according to the present invention can be used to reduce the microbial load of different types of liquids. Treatable liquids include liquids containing gases, solids and/or liquid substances. They may have higher or lower viscosities and therefore also take the form of mixtures, slurries, emulsions, gels and the like.

Preferably, the liquid is selected from: food liquid, for human and animal consumption (e.g. water, milk, oil, wine, fruit juices, canned food, jam, etc.); cosmetic liquid (e.g. cream, lotion, emulsions, gels, foams, oils, soaps, perfumes, toothpaste, etc.); biological liquid (e.g. blood, urine); hydrocarbon liquid (e.g. lubricants, coolants, fuels, oil drilling sludge, etc.); liquid waste (civil or industrial waste water, sewage, sludge from water purification plants, etc.), heat transfer liquid (e.g. cooling and heating liquids for boilers, evaporative towers, heat exchangers, etc.).

Preferably, the treated liquid has a viscosity at <NUM> within the range <NUM> mPa·s - <NUM>*<NUM><NUM> mPa-s (measured with Brookfield viscometer).

The treatment with infrared radiation according to the present invention makes it possible to reduce the microbial load present in a liquid due to the presence of microorganisms such as, for example, bacteria, viruses, yeasts and moulds. Examples of microorganisms are: Enterobacteriaceae, Escherichia coli, Salmonella Spp. , Bacillus cereus, Staphylococcus aureus and Listeria Spp.

To further illustrate the features of the present invention, the following example embodiment is provided, which should be understood as illustrating the present invention and not in a sense limiting the scope of protection defined by the appended claims.

The effectiveness of the present invention was tested on samples of a liquid food consisting of reconstituted skimmed milk powder having a dry residue of about <NUM>/<NUM> of product. To this end, a treatment module was set up consisting of a tubular conduit made entirely of quartz transparent to infrared radiation, having a diameter of <NUM> and a length of <NUM>. A system of irradiation of infrared radiations was placed on the outer circumference of the tube, comprising <NUM> IR filament sources (each developing linearly for a length equal to <NUM> in a direction parallel to the longitudinal axis of the tubular conduit and having a power equal to <NUM>,<NUM> W) arranged along the axial direction of the tubular conduit at a distance r equal to <NUM>. The source was set to radiate towards the flow cavity of the tubular conduit an IR radiation of wavelength <NUM> - <NUM> micrometers.

The liquid was made to flow into the module at a flow rate of <NUM>/min. The total volume of liquid treated was <NUM> litres.

Under the aforesaid conditions, the total duration of the treatment, corresponding to the time taken for the liquid advancing front to cross the entire length of the tubular conduit, was <NUM> seconds.

The effectiveness of the treatment in reducing the microbial load in the liquid was assessed by comparing the results of microbiological analyses conducted on a sample of the liquid before and after the treatment. The results of the analyses and the methods of analysis used are given in Table <NUM> below, where the extent of reduction in microbial load is expressed in terms of logarithmic reduction per gram of sample (logarithm of the ratio of the number of initial microorganisms to the number of microorganisms after the treatment).

No significant differences were shown in the product before and after the treatment according to the invention in relation to the rheological (viscosity), organoleptic and colour characteristics.

Claim 1:
Method for reducing the microbial load of a liquid comprising the following phases:
a. providing at least one treatment module (<NUM>) comprising:
- at least one tubular conduit (<NUM>) having at least one portion (<NUM>) transparent to infrared radiation;
- three sources (16a, 16b, 16c) of infrared radiation located in the vicinity of said portion (<NUM>) transparent to infrared radiation, said three sources (16a, 16b, 16c) being positioned along a direction parallel to the longitudinal axis of said tubular conduit (<NUM>), at a distance r from each other, and being configured to transmit at least one infrared radiation (<NUM>);
b. making the liquid (<NUM>) flow into said tubular conduit (<NUM>);
c. exposing the liquid (<NUM>) while it flows inside the tubular conduit (<NUM>) to the infrared radiation (<NUM>) emitted by said three sources (16a, 16b, 16c);
wherein the liquid flowing inside the tubular conduit is treated according to an irradiation sequence comprising:
i) first exposure of the liquid to infrared radiation for a time within the range <NUM> - <NUM> seconds, which is a first heating phase;
ii) second exposure of the liquid to infrared radiation for a time within the range <NUM> - <NUM> seconds, which is a second heating phase;
iii) third exposure of the liquid to infrared radiation for a time within the range <NUM> - <NUM> seconds, which is a third heating phase;
wherein said phases i), ii) and iii) are interspersed with periods of non-exposure of the liquid to infrared radiation of duration within the range <NUM> - <NUM> seconds. seconds, which are cooling phases.