WO2018041417A1 - Method for sterilizing gas dispersed liquids - Google Patents
Method for sterilizing gas dispersed liquids Download PDFInfo
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- WO2018041417A1 WO2018041417A1 PCT/EP2017/025248 EP2017025248W WO2018041417A1 WO 2018041417 A1 WO2018041417 A1 WO 2018041417A1 EP 2017025248 W EP2017025248 W EP 2017025248W WO 2018041417 A1 WO2018041417 A1 WO 2018041417A1
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- Prior art keywords
- liquid
- aerosol
- milk
- dispersed
- gas
- Prior art date
Links
- 239000007788 liquid Substances 0.000 title claims abstract description 53
- 238000000034 method Methods 0.000 title claims abstract description 39
- 230000001954 sterilising effect Effects 0.000 title claims description 12
- 239000000443 aerosol Substances 0.000 claims abstract description 34
- 239000007789 gas Substances 0.000 claims description 22
- 239000006185 dispersion Substances 0.000 claims description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 6
- 239000002245 particle Substances 0.000 claims description 6
- 230000001678 irradiating effect Effects 0.000 claims description 5
- 239000011261 inert gas Substances 0.000 claims description 4
- 239000008263 liquid aerosol Substances 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- 235000013336 milk Nutrition 0.000 abstract description 41
- 239000008267 milk Substances 0.000 abstract description 41
- 210000004080 milk Anatomy 0.000 abstract description 41
- 230000005855 radiation Effects 0.000 abstract description 14
- 238000004659 sterilization and disinfection Methods 0.000 abstract description 10
- 235000013305 food Nutrition 0.000 abstract description 6
- 239000012535 impurity Substances 0.000 abstract description 6
- 244000005700 microbiome Species 0.000 abstract description 6
- 235000011389 fruit/vegetable juice Nutrition 0.000 abstract description 5
- 238000004519 manufacturing process Methods 0.000 abstract description 5
- 230000002906 microbiologic effect Effects 0.000 abstract description 5
- 235000013361 beverage Nutrition 0.000 abstract description 4
- 235000020188 drinking water Nutrition 0.000 abstract description 4
- 239000003651 drinking water Substances 0.000 abstract description 4
- 230000003287 optical effect Effects 0.000 abstract description 4
- 244000052769 pathogen Species 0.000 abstract description 4
- 235000010633 broth Nutrition 0.000 abstract description 3
- 239000002537 cosmetic Substances 0.000 abstract description 3
- 239000010840 domestic wastewater Substances 0.000 abstract description 3
- 235000015097 nutrients Nutrition 0.000 abstract description 3
- 239000000047 product Substances 0.000 description 9
- 230000000694 effects Effects 0.000 description 5
- 239000010453 quartz Substances 0.000 description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 5
- 238000013019 agitation Methods 0.000 description 4
- 235000021056 liquid food Nutrition 0.000 description 4
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 3
- 238000009928 pasteurization Methods 0.000 description 3
- 241000700605 Viruses Species 0.000 description 2
- 230000002411 adverse Effects 0.000 description 2
- 230000000844 anti-bacterial effect Effects 0.000 description 2
- 239000003925 fat Substances 0.000 description 2
- 239000012263 liquid product Substances 0.000 description 2
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 2
- 229910052753 mercury Inorganic materials 0.000 description 2
- 244000005706 microflora Species 0.000 description 2
- 239000007800 oxidant agent Substances 0.000 description 2
- 230000001717 pathogenic effect Effects 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000007669 thermal treatment Methods 0.000 description 2
- 238000009281 ultraviolet germicidal irradiation Methods 0.000 description 2
- 108020000946 Bacterial DNA Proteins 0.000 description 1
- 102000014171 Milk Proteins Human genes 0.000 description 1
- 108010011756 Milk Proteins Proteins 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 235000013365 dairy product Nutrition 0.000 description 1
- 230000009849 deactivation Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 230000001066 destructive effect Effects 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 235000020191 long-life milk Nutrition 0.000 description 1
- 235000021239 milk protein Nutrition 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 239000003206 sterilizing agent Substances 0.000 description 1
- 235000013343 vitamin Nutrition 0.000 description 1
- 239000011782 vitamin Substances 0.000 description 1
- 229940088594 vitamin Drugs 0.000 description 1
- 229930003231 vitamin Natural products 0.000 description 1
- 150000003722 vitamin derivatives Chemical class 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 235000008939 whole milk Nutrition 0.000 description 1
Classifications
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
- A23L3/00—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs
- A23L3/26—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by irradiation without heating
- A23L3/28—Preservation of foods or foodstuffs, in general, e.g. pasteurising, sterilising, specially adapted for foods or foodstuffs by irradiation without heating with ultraviolet light
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23C—DAIRY PRODUCTS, e.g. MILK, BUTTER OR CHEESE; MILK OR CHEESE SUBSTITUTES; MAKING THEREOF
- A23C3/00—Preservation of milk or milk preparations
- A23C3/07—Preservation of milk or milk preparations by irradiation, e.g. by microwaves ; by sonic or ultrasonic waves
- A23C3/076—Preservation of milk or milk preparations by irradiation, e.g. by microwaves ; by sonic or ultrasonic waves by ultraviolet or infrared radiation
-
- A—HUMAN NECESSITIES
- A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
- A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
- A23L2/00—Non-alcoholic beverages; Dry compositions or concentrates therefor; Their preparation
- A23L2/42—Preservation of non-alcoholic beverages
- A23L2/50—Preservation of non-alcoholic beverages by irradiation or electric treatment without heating
Definitions
- the present invention relates to the methods for deactivating microorganisms, including pathogens, in liquids, and may be used in the food industry to sterilize milk.
- the invention may also be used in the juice and other beverage industries, in drinking water production, as well as in cosmetic and healthcare practices, domestic wastewater and food plant process effluent disinfection, and in the microbiological industry to sterilize liquid nutrient broths.
- the invention When employed in any of the above areas, the invention enables pathogen and virus deactivation.
- the first device for treating milk with UV-irradiation was designed in France in 1900.
- a Kuhn quartz mercury lamp generating rays with a wave length of approximately 254 nm was used as a UV-radiation source. It was demonstrated that UV radiation enables sterilization of milk with little or no loss of most of its properties, while preserving all of its organoleptic properties.
- UV radiation to treat milk is the low penetrating power of UV rays, i.e. they are almost completely absorbed by a layer of milk with a thickness of approximately 50 micron without any significant effect on the bulk of the product under treatment.
- UV treatment of nearly any liquid food products, including water provides a similar effect.
- microflora deactivating in milk (SU 1450804) is as follows: milk is poured into quartz tubes and centrifuged to separate insoluble impurities. The treated milk is then UV-irradiated in an approximately 0.1 mm-thick layer with an ORK-2 bactericidal lamp as the source of radiation. If agitation, as well as repeated and sufficiently long-time irradiation is provided, nearly all microorganism cells in milk may be killed.
- a disadvantage of the above method is its low productivity, frequency and complexity of using thereof for large-scale industrial applications.
- Another known method (RU232281 1 ) is free from some of the above disadvantages.
- milk is pre-treated to remove mechanical impurities, homogenized and UV-irradiated 3 to 5 times in leak-tight reactors arranged in series, thoroughly agitating the milk after each irradiation cycle.
- Such repeated treatment provides for continuous process and irradiation exposure as required for bacterial DNA degradation, while agitation provides for the treatment of a new layer of milk during each cycle.
- the method does not address the main issue of inadequate efficiency of irradiating milk with UV rays due to their poor ability to penetrate into the bulk of the product. Though thorough agitation addresses this disadvantage to some extent, it also makes the process and equipment substantially more complex and increases power consumption.
- the closest to the claimed invention is a method for sterilizing milk and other liquids that comprises ozonizing the liquid using an injector to form a liquid dispersion, turbulizing, and irradiating it with UV rays, while agitating the liquid, and then separating gas from the liquid (RU 2058096 C1 , published 20.04.1996; CA 2139924 A1 , published 24.1 1 .1994).
- the resulting dispersion is a gas emulsion, where the dispersed phase is the gas (ozone), and the liquid is the dispersion phase.
- the method does not address the main disadvantage related to UV radiation's poor ability to penetrate into the bulk of the liquid product.
- powerful sources of UV radiation have to be used, and the process is complicated.
- the objective of the present invention is to provide a process with improved efficiency of UV radiating liquids by improving penetrating ability of UV radiation.
- This objective is achieved through a liquid sterilization method, comprising: producing a dispersed liquid, irradiating the resulting dispersion with UV rays, and separating the liquid, wherein the dispersion is produced by filling an intake reservoir of an aerosol generator with the liquid and then by dispersing the liquid in a gas medium to obtain an aerosol, and then the aerosol is delivered to a leak- tight chamber and irradiated with UV rays.
- the liquid is dispersed in a gas medium by hydraulic, or pneumatic, or ultrasonic atomizing.
- air or an inert gas, or nitrogen, is used as the gas medium.
- the liquid is separated by centrifuging or cycloning the aerosol.
- the hydraulic atomizing is carried out at a rate of 0.1 to 25 l/min.
- the pneumatic atomizing is carried out at ratio of gas (m3/hour) to liquid (l/min) ranging from 5 to 20.
- liquid aerosol is generated preferably at an ultrasonic frequency of 50 kHz with approximately 5 micron liquid particles as the dispersed phase.
- the total dose of UV-radiation is approximately 20 mJ/cm 2 .
- the essence of the invention is that a liquid, more particularly milk, treated to remove mechanical impurities, is dispersed in air to obtain a stable aerosol, and in this particular state is UV-irradiated.
- Aerosolized milk is in a finely dispersed state and forms a dispersed phase evenly distributed in an air (gas) dispersion phase. Since optical density of the aerosol is incomparably lower than the initial milk optical density, UV radiation's ability to penetrate into the bulk of the product is multiplied. Thus, efficient impact is provided on microorganisms within an aerosol layer with a thickness ranging from tens of millimeters to tens of centimeters depending on the aerosol density. Estimation results show that the UV-irradiation exposure (1 6-40 mJ/cm 2 ), required to obtain a substantially sterile product under static conditions, is achieved by an order of magnitude more efficiently than if liquid milk were irradiated.
- the dispersion is produced by dispersing the liquid in a gas medium to obtain an aerosol.
- the liquid is dispersed for example in a gas medium by hydraulic, or pneumatic, or ultrasonic atomizing.
- air, or an inert gas, or nitrogen is used as the gas medium.
- the liquid is separated for example by centrifuging or cycloning the aerosol.
- the hydraulic atomizing is carried out at a rate of 0.1 to 25 l/min.
- the air atomizing with the gas (m3/hour) to liquid (l/min) is carried out at ratio ranging from 5 to 20.
- the liquid aerosol is generated at an ultrasonic frequency of 50 kHz with approximately 5 micron liquid particles as the dispersed phase.
- the total dose of UV-radiation is approximately 20 mJ/cm2.
- Milk or other liquid may be dispersed in a gas using various methods and devices.
- such well developed in theory and in practice devices as ultrasonic dispersers of the types described in the patents RU 2254934 or US 4,159,803, operating at an ultrasonic frequency of 40 to 100 kHz, or conventional atomizing aerosol generators having slot atomizers to form a two-dimensional linear jet, generating an aerosol with the dispersed phase particle size of 1 to 10 microns.
- Liquid is dispersed for example by hydraulic atomizing at a rate of 0.1 to 25 l/min or air atomizing with the gas (m 3 /hour) to liquid (l/min) ratio ranging from 5 to 20.
- Liquid may be air, inert gas, or nitrogen-atomized.
- Aerosolized milk particle size and density may be changed by varying the dispersing conditions: milk temperature, ultrasonic vibration frequency and strength, or atomizer diameter and gas pressure within the aerosol generator.
- Various sources of UV radiation may be used, such as mercury quartz or bactericidal lamps generating radiation with a fundamental wave length of 254 nm, as well as light-emitting semiconductor diodes.
- To generate UV radiation most advantageous are low pressure ozone-free lamps. Using them does not result in ozone formation, which, as noted above, is a powerful oxidizer that oxidizes milk fats and adversely changes the chemical structure of other milk constituents.
- the UV-treated milk aerosol may then be broken by centrifuging or cycloning to obtain a homogenous liquid product, i.e. milk, with microbiological content fully complying with applicable sanitation and hygiene standards, while preserving its biological value and organoleptic properties.
- the provided method features low power consumption, is readily adaptable to commercial scale production, while ensuring high efficiency of the milk sterilization process.
- MUSAG medical ultrasonic aerosol generator
- Aerosol was then delivered to a leak-tight cylindrical chamber, configured as quartz tube 5 cm in diameter, with three UV lamps arranged outside the quartz tube at equally spaced locations around its circumference, where the milk was exposed to UV-radiation with the wave length 253,7 nm and with a total dose of approximately 20 mJ/cm 2 .
- the UV-treated aerosol was then delivered to a cyclone, configured as a conical vessel comprising a tangential inlet and a bottom outlet pipe, where the aerosol was broken and the resulting liquid milk exits the cyclone through the bottom drain pipe.
- the resulting product features good organoleptic properties and a pathogen and virus content not exceeding the standards established for sterilized milk.
- other liquids such as juices, other beverages, drinking water were sterilizes exactly in the same way.
- the proposed method for sterilizing of liquids may be employed in the food industry to disinfect milk, in the juice and other beverage production industries, in drinking water production, as well as in cosmetic and healthcare practices, domestic wastewater and food plant process effluent disinfection, and in the microbiological industry to sterilize liquid nutrient broths, using the existing industrial equipment.
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- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
- Polymers & Plastics (AREA)
- Nutrition Science (AREA)
- Toxicology (AREA)
- Apparatus For Disinfection Or Sterilisation (AREA)
- Physical Water Treatments (AREA)
Abstract
The invention relates to the methods for deactivating microorganisms, including pathogens, in liquids, and may be used in the food industry to sterilize milk. The invention may also be used in the juice and other beverage industries, in drinking water production, as well as in cosmetic and healthcare practices, domestic wastewater and food plant process effluent disinfection, and in the microbiological industry to sterilize liquid nutrient broths. The essence of the invention is that a liquid, more particularly milk, treated to remove mechanical impurities, is dispersed in air to obtain a stable aerosol, and in this particular state is UV-irradiated. Since optical density of the aerosol is incomparably lower than the initial milk optical density, UV radiation's ability to penetrate into the bulk of the product is multiplied. Thus, efficient impact is provided on microorganisms within an aerosol layer with a thickness ranging from tens of millimeters to tens of centimeters depending on the aerosol density.
Description
Method for sterilizing gas dispersed liquids
TECHNICAL FIELD
The present invention relates to the methods for deactivating microorganisms, including pathogens, in liquids, and may be used in the food industry to sterilize milk. The invention may also be used in the juice and other beverage industries, in drinking water production, as well as in cosmetic and healthcare practices, domestic wastewater and food plant process effluent disinfection, and in the microbiological industry to sterilize liquid nutrient broths.
When employed in any of the above areas, the invention enables pathogen and virus deactivation.
PRIOR ART
Most of the current treatment methods for reducing microbiological activity or completely deactivating various microorganisms in milk and other liquid food products are based on thermal treatment. They primarily include such well-known methods as pasteurization and sterilization.
Relatively simple and reliable, the above methods have a wide range of industrial applications. However, they have a common disadvantage consisting in that achievement of the desired effect requires high power consumption, and in the adverse impact on labile components of milk and other liquid food products that degrades their biological value. For example, pasteurization and, particularly, sterilization of milk entail destructive structural changes of milk proteins undesirably affecting both their biological value and the whole range of their functional properties. Thermal treatment of juices is detrimental to the vitamin activity in them and significantly deteriorates their organoleptic properties. UV treatment of liquid food products is an alternative method providing an effect similar or close to that of thermal pasteurization or sterilization.
The first device for treating milk with UV-irradiation was designed in France in 1900. A Kuhn quartz mercury lamp generating rays with a wave length of approximately 254 nm was used as a UV-radiation source.
It was demonstrated that UV radiation enables sterilization of milk with little or no loss of most of its properties, while preserving all of its organoleptic properties.
Further studies confirmed that using UV radiation allowed deactivating of undesirable microflora in milk by at least 99.9 %, and advancements in the UV radiator design facilitated the development of devices suitable for industrial applications (US2072417; Veisseyre, R., Techniques laitieres ("Dairy Techniques"), Moscow, Kolos, 1971 ).
An essential disadvantage limiting wider use of UV radiation to treat milk is the low penetrating power of UV rays, i.e. they are almost completely absorbed by a layer of milk with a thickness of approximately 50 micron without any significant effect on the bulk of the product under treatment.
UV treatment of nearly any liquid food products, including water, provides a similar effect.
Repeated attempts have been made to improve UV radiation's efficiency as a sterilizing agent. They primarily focused on increasing the output of UV radiation sources, hardware design, treatment frequency, and agitation rate (Patents RU 2395461 ; US 5451791 ; US 7270748).
One known method for microflora deactivating in milk (SU 1450804) is as follows: milk is poured into quartz tubes and centrifuged to separate insoluble impurities. The treated milk is then UV-irradiated in an approximately 0.1 mm-thick layer with an ORK-2 bactericidal lamp as the source of radiation. If agitation, as well as repeated and sufficiently long-time irradiation is provided, nearly all microorganism cells in milk may be killed.
A disadvantage of the above method is its low productivity, frequency and complexity of using thereof for large-scale industrial applications.
Another known method (RU232281 1 ) is free from some of the above disadvantages. According to this method, milk is pre-treated to remove mechanical impurities, homogenized and UV-irradiated 3 to 5 times in leak-tight reactors arranged in series, thoroughly agitating the milk after each irradiation cycle.
Such repeated treatment provides for continuous process and irradiation exposure as required for bacterial DNA degradation, while agitation provides for the treatment of a new layer of milk during each cycle.
However, despite its certain advantages, the method does not address the main issue of inadequate efficiency of irradiating milk with UV rays due to their poor ability to penetrate into the bulk of the product. Though thorough agitation addresses this disadvantage to some extent, it also makes the process and equipment substantially more complex and increases power consumption.
The closest to the claimed invention is a method for sterilizing milk and other liquids that comprises ozonizing the liquid using an injector to form a liquid dispersion, turbulizing, and irradiating it with UV rays, while agitating the liquid, and then separating gas from the liquid (RU 2058096 C1 , published 20.04.1996; CA 2139924 A1 , published 24.1 1 .1994). The resulting dispersion is a gas emulsion, where the dispersed phase is the gas (ozone), and the liquid is the dispersion phase.
However, despite its certain advantages, the method does not address the main disadvantage related to UV radiation's poor ability to penetrate into the bulk of the liquid product. As a result, powerful sources of UV radiation have to be used, and the process is complicated. Use of ozone, being a powerful oxidizer, typically results in substantial changes in the chemical nature of fats and other milk components.
SUMMARY OF THE INVENTION
The objective of the present invention is to provide a process with improved efficiency of UV radiating liquids by improving penetrating ability of UV radiation. This objective is achieved through a liquid sterilization method, comprising: producing a dispersed liquid, irradiating the resulting dispersion with UV rays, and separating the liquid, wherein the dispersion is produced by filling an intake reservoir of an aerosol generator with the liquid and then by dispersing the liquid in a gas medium to obtain an aerosol, and then the aerosol is delivered to a leak- tight chamber and irradiated with UV rays.
In alternative embodiments of the invention, the liquid is dispersed in a gas medium by hydraulic, or pneumatic, or ultrasonic atomizing.
In alternative embodiments air, or an inert gas, or nitrogen, is used as the gas medium. In alternative embodiments the liquid is separated by centrifuging or cycloning the aerosol.
In alternative embodiments the hydraulic atomizing is carried out at a rate of 0.1 to 25 l/min.
In alternative embodiments the pneumatic atomizing is carried out at ratio of gas (m3/hour) to liquid (l/min) ranging from 5 to 20.
In alternative embodiments the liquid aerosol is generated preferably at an ultrasonic frequency of 50 kHz with approximately 5 micron liquid particles as the dispersed phase.
In alternative embodiments the total dose of UV-radiation is approximately 20 mJ/cm2.
The essence of the invention is that a liquid, more particularly milk, treated to remove mechanical impurities, is dispersed in air to obtain a stable aerosol, and in this particular state is UV-irradiated.
Aerosolized milk is in a finely dispersed state and forms a dispersed phase evenly distributed in an air (gas) dispersion phase. Since optical density of the aerosol is incomparably lower than the initial milk optical density, UV radiation's ability to penetrate into the bulk of the product is multiplied. Thus, efficient impact is provided on microorganisms within an aerosol layer with a thickness ranging from tens of millimeters to tens of centimeters depending on the aerosol density. Estimation results show that the UV-irradiation exposure (1 6-40 mJ/cm2), required to obtain a substantially sterile product under static conditions, is achieved by an order of magnitude more efficiently than if liquid milk were irradiated.
It will be noted that low viscosity of the gas medium provides for efficient convective mixing of the whole milk aerosol volume, thus further improving the uniformity and rate of the milk disinfection process.
DETAILED DESCRIPTION OF THE INVENTION
The present invention, method for sterilizing the liquids comprises following steps: pretreating the liquid to remove mechanical impurities; filling an intake reservoir of a aerosol generator with the liquid; producing a dispersed liquid aerosol; delivering the aerosol to a leak-tight cylindrical chamber; irradiating the resulting aerosol with UV rays; delivering the UV-treated aerosol to a cyclone or a centrifuge; separating the liquid by broking the aerosol and leading the resulting liquid out from the cyclone or centrifuge.
The dispersion is produced by dispersing the liquid in a gas medium to obtain an aerosol. The liquid is dispersed for example in a gas medium by hydraulic, or pneumatic, or ultrasonic atomizing. For example air, or an inert gas, or nitrogen, is used as the gas medium. The liquid is separated for example by centrifuging or cycloning the aerosol.
The hydraulic atomizing is carried out at a rate of 0.1 to 25 l/min. The air atomizing with the gas (m3/hour) to liquid (l/min) is carried out at ratio ranging from 5 to 20. The liquid aerosol is generated at an ultrasonic frequency of 50 kHz with approximately 5 micron liquid particles as the dispersed phase. The total dose of UV-radiation is approximately 20 mJ/cm2.
Milk or other liquid may be dispersed in a gas using various methods and devices. For example, such well developed in theory and in practice devices as ultrasonic dispersers of the types described in the patents RU 2254934 or US 4,159,803, operating at an ultrasonic frequency of 40 to 100 kHz, or conventional atomizing aerosol generators having slot atomizers to form a two-dimensional linear jet, generating an aerosol with the dispersed phase particle size of 1 to 10 microns. Liquid is dispersed for example by hydraulic atomizing at a rate of 0.1 to 25 l/min or air atomizing with the gas (m3/hour) to liquid (l/min) ratio ranging from 5 to 20.
Liquid may be air, inert gas, or nitrogen-atomized.
Aerosolized milk particle size and density may be changed by varying the dispersing conditions: milk temperature, ultrasonic vibration frequency and strength, or atomizer diameter and gas pressure within the aerosol generator.
Various sources of UV radiation may be used, such as mercury quartz or bactericidal lamps generating radiation with a fundamental wave length of 254 nm, as well as light-emitting semiconductor diodes. To generate UV radiation, most advantageous are low pressure ozone-free lamps. Using them does not result in ozone formation, which, as noted above, is a powerful oxidizer that oxidizes milk fats and adversely changes the chemical structure of other milk constituents.
The UV-treated milk aerosol may then be broken by centrifuging or cycloning to obtain a homogenous liquid product, i.e. milk, with microbiological content fully complying with applicable sanitation and hygiene standards, while preserving its biological value and organoleptic properties.
The provided method features low power consumption, is readily adaptable to commercial scale production, while ensuring high efficiency of the milk sterilization process.
Below is an example illustrating the essence of the proposed invention. Example of the method according to the present invention.
Milk, pretreated to remove mechanical impurities, was filled into an intake reservoir of an ultrasonic aerosol generator MUSAG (medical ultrasonic aerosol generator), where a milk aerosol was generated at an ultrasonic frequency of 50 kHz at the temperature 40°C with approximately 5 micron milk particles as the dispersed phase.
Aerosol was then delivered to a leak-tight cylindrical chamber, configured as quartz tube 5 cm in diameter, with three UV lamps arranged outside the quartz tube at equally spaced locations around its circumference, where the milk was exposed to UV-radiation with the wave length 253,7 nm and with a total dose of approximately 20 mJ/cm2.
The UV-treated aerosol was then delivered to a cyclone, configured as a conical vessel comprising a tangential inlet and a bottom outlet pipe, where the aerosol was broken and the resulting liquid milk exits the cyclone through the bottom drain pipe. The resulting product features good organoleptic properties and a pathogen and virus content not exceeding the standards established for sterilized milk.
In alternative embodiments other liquids, such as juices, other beverages, drinking water were sterilizes exactly in the same way.
The proposed method for sterilizing of liquids may be employed in the food industry to disinfect milk, in the juice and other beverage production industries, in drinking water production, as well as in cosmetic and healthcare practices, domestic wastewater and food plant process effluent disinfection, and in the microbiological industry to sterilize liquid nutrient broths, using the existing industrial equipment.
Claims
1 . A method for sterilizing gas dispersed liquids, comprising: producing a dispersed liquid, irradiating the resulting dispersion with UV rays, and separating the liquid, wherein the dispersion is produced by filling an intake reservoir of an aerosol generator with the liquid and then by dispersing the liquid in a gas medium to obtain an aerosol, and then the aerosol is delivered to a leak-tight chamber and irradiated with UV rays.
2. The method of claim 1 , wherein the liquid is dispersed in a gas medium by hydraulic, or pneumatic, or ultrasonic atomizing.
3. The method of claim 1 , wherein air, or an inert gas, or nitrogen, is used as the gas medium.
4. The method of claim 1 , wherein the liquid is separated from aerosolized liquid by centrifuging or cycloning the aerosol.
5. The method of claim 2, wherein the hydraulic atomizing is carried out at a rate of 0.1 to 25 l/min.
6. The method of claim 2, wherein the air atomizing is carried out at ratio of gas (m3/hour) to liquid (l/min) ranging from 5 to 20.
7. The method of claim 2, wherein the liquid aerosol is generated at an ultrasonic frequency of 50 kHz with approximately 5 micron liquid particles as the dispersed phase.
8. The method of claim 1 , wherein the total dose of UV-radiation is approximately 20 mJ/cm2.
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EEP201600019 | 2016-08-31 | ||
EEP201600019 | 2016-08-31 |
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Citations (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB191308500A (en) * | 1913-04-10 | 1914-02-19 | Reginald Frank Edwards | Improvements relating to the Sterilisation of Liquids. |
US2072417A (en) | 1934-01-19 | 1937-03-02 | R U V Engineering Corp | Method of irradiating substances with active rays |
US4159803A (en) | 1977-03-31 | 1979-07-03 | MistO2 Gen Equipment Company | Chamber for ultrasonic aerosol generation |
SU1450804A1 (en) | 1986-03-10 | 1989-01-15 | Алтайский филиал Всесоюзного научно-исследовательского института маслодельной и сыродельной промышленности | Method of inactivating milk microflora |
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