Method and device for ultra-high pressure jet sterilization of liquid

Abstract

Provided in the present disclosure are a method and device for ultra-high pressure jet sterilization of a liquid, which method comprises pressurizing a liquid to above 50 MPa to form a jet; and causing the jet to pass through a microscreen filter screen, wherein the pore size of the microscreen filter screen is 0.1-1 microns, and the thickness of the microscreen filter screen is 0.5-1.5 microns. The method and device for ultra-high pressure jet sterilization of a liquid in combination with the microscreen filter screen of the present disclosure enable‌ separation and substantial eradication of microorganisms in the liquid,‌ while simultaneously achieving highly efficient retention‌ of beneficial bioactive molecules and beneficial thermosensitive substances in the liquid.

Description

Method and apparatus for ultra-high pressure jet sterilization of liquids

[0001] Cross-reference to related applications

[0002] The present disclosure claims priority to Chinese Patent Application No. 202410465647.5, filed on April 18, 2024, which is hereby incorporated by reference in its entirety. TECHNICAL FIELD

[0003] The present disclosure relates to the technical field of liquid sterilization, in particular to a method and apparatus for ultra-high pressure jet sterilization of liquids. BACKGROUND

[0004] Ultra-high pressure jet originates from the "water jet" cutting technology in the fields of chemical industry, metallurgy, construction, etc., i.e. high pressure water jet cutting technology. Through a pressurizing device such as a high pressure reciprocating plunger pump, ordinary water is pressurized to tens, hundreds or even thousands of atmospheres and then sprayed out from various different shaped nozzles, forming a high speed water jet with strong penetration ability, the jet speed of which can reach or even exceed 1000 m / s.

[0005] During the ultra-high pressure jet treatment process, the material is subjected to a violent collision, which can generate effects such as high-speed liquid impact, strong shear, cavitation explosion, high-speed oscillation, etc. When these effects are applied to microorganisms such as bacteria, they can cause the bacteria to break apart, leading to the death of the microorganisms. Therefore, the way of forming an ultra-high pressure jet of the target liquid has been adopted to sterilize the liquid.

[0006] The current ultra-high pressure jet sterilization method usually adopts the way of making the jet collide with the container wall or the jet collide to sterilize, and can simultaneously achieve the effects of ultra-micronization, micro-emulsification and homogenization.

[0007] However, the inventors of the present disclosure surprisingly found that in the fields of food, medicine, etc., the liquid to be sterilized can also contain other beneficial bioactive molecules such as nutritional components or active ingredients, e.g. proteins, fats, etc., in addition to bacteria. In this case, these bioactive molecules can also undergo structural changes, e.g. be broken apart, under the action of the ultra-high pressure jet, leading to changes in the final properties and functions of the liquid after sterilization. In addition, during the violent collision process, there is always a process of mechanical energy being converted into heat energy, leading to an increase in the temperature of the fluid, which can affect the retention of some beneficial heat-sensitive substances, especially heat-sensitive flavor substances or nutritional substances, in the liquid to be sterilized. Therefore, a simple ultra-high pressure jet sterilization method can not be able to remove microorganisms efficiently while also retaining beneficial bioactive molecules and beneficial heat-sensitive substances. The inventors further surprisingly found that the above problems are particularly disadvantageous in the case of using ultra-high pressure jet technology to sterilize liquid milk such as cow milk.

[0008] Therefore, there is a need for improvement in the high-pressure jet sterilization technology of liquid, especially liquid milk, in the field of food and the like.

[0009] SUMMARY

[0010] In one aspect, the present disclosure provides a method for high-pressure jet sterilization of liquid, characterized in that the method comprises: pressurizing the liquid to 50 MPa or above and forming a jet; and passing the jet through a microsieve filter having a pore size of 0.1 to 1 micron and a thickness of 0.5 to 1.5 microns.

[0011] Optionally, the microsieve filter has a porosity ranging from 75% to 85%.

[0012] Optionally, the microsieve filter is an anisotropic microsieve filter.

[0013] Optionally, the liquid is pressurized to 50 MPa to 350 MPa.

[0014] Optionally, the temperature of the microsieve filter is maintained at 55°C or below.

[0015] Optionally, the liquid is liquid milk, preferably cow milk, wherein the liquid milk is pressurized to 200 MPa to 250 MPa to form a jet.

[0016] Further optionally, the method further comprises a pretreatment before pressurizing the liquid milk, the pretreatment comprising milk cleaning and bacteria-removing centrifugal treatment to remove at least part of macromolecular impurities.

[0017] Further optionally, the temperature of the microsieve filter is maintained at 2°C to 6°C.

[0018] Further optionally, the method further comprises a cooling treatment of the liquid milk before forming the jet, wherein the liquid milk is cooled to 2°C to 6°C.

[0019] In another aspect, the present disclosure provides an apparatus for high-pressure jet sterilization of liquid, characterized in that the apparatus comprises: a high-pressure jet generating device comprising a pressurizing component for pressurizing the liquid to 50 MPa or above and a jet nozzle; and a microsieve filter facing the jet nozzle, the microsieve filter having a pore size of 0.1 to 1 micron and a thickness of 0.5 to 1.5 microns.

[0020] Optionally, the microsieve filter has a porosity ranging from 75% to 85%.

[0021] Optionally, the microsieve filter is an anisotropic microsieve filter.

[0022] Optionally, the apparatus has a microsieve filter temperature control device.

[0023] Optionally, the microsieve comprises one or more of the following materials: synthetic diamond, natural diamond, and graphene. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a schematic flow chart of ultra-high pressure jet sterilization of liquid milk according to one embodiment of the method of the present disclosure.

[0025] Figure 2 is a schematic diagram of one embodiment of the apparatus according to the present disclosure.

[0026] Figure 3 is a schematic diagram of the nozzle and microsieve cooperation according to one embodiment of the apparatus of the present disclosure. DETAILED DESCRIPTION

[0027] How to develop a new type of ultra-high pressure jet sterilization method in view of the foregoing deficiencies in the prior art is an important technical direction that needs to be researched and solved in the field. The desired ultra-high pressure jet sterilization method can kill microorganisms in the liquid using ultra-high pressure jet, while efficiently retaining beneficial bioactive molecules and beneficial heat-sensitive substances in the liquid, so as to meet the processing needs of ensuring the quality and nutrition of products with different characteristics while sterilizing

[0028] The method and apparatus of the present disclosure cooperate with the microsieve to sterilize the liquid using ultra-high pressure jet, which can separate and substantially completely kill microorganisms in the liquid, while efficiently retaining beneficial bioactive molecules and beneficial heat-sensitive substances in the liquid.

[0029] The inventors introduced the concept of microsieve processing ultra-high pressure jet in view of the deficiencies of the existing ultra-high pressure jet technology, and cooperated with the microsieve to process the liquid using ultra-high pressure jet. According to the size characteristics of the beneficial bioactive molecules which are smaller than the harmful microorganisms, the microsieve filtration technology suitable for ultra-high pressure jet was adopted to at least partially solve the above problems. The inventors found that the use of appropriate microsieve can more accurately separate microorganisms and beneficial bioactive molecules. In one embodiment, the accurate separation achieves a microorganism reduction ratio of 10 -7In the case of the present application, the liquid to be treated is pressurized to 50 MPa or higher, such as 50 MPa to 350 MPa, and a jet is formed through a nozzle. The high-pressure jet is directed to a microsieve filter downstream under the drive of strong hydraulic energy, and passes through the sieve holes with a specific pore size. In this process, microorganisms with a size larger than the pore size are intercepted on the microsieve filter and are impacted and broken, while beneficial bioactive molecules with a size smaller than the pore size can pass through the pores of the microsieve filter without being subjected to a strong impact, avoiding the damage caused by the collision of the high-pressure jet with the container wall in conventional technology. Thus, the efficient removal of microorganisms and the retention of beneficial bioactive molecules are taken into account. On the other hand, compared with the impurity removal technology using only membrane filtration, the combination of microsieve filter and high-pressure jet allows bacteria to be broken and killed on the filter, and the fragments can also pass through the filter. This can avoid the problems of material interception and membrane hole blockage in conventional membrane filtration technology, greatly reducing the waste of materials.

[0030] In one embodiment, the present disclosure provides a method for high-pressure jet sterilization of a liquid, characterized in that the method comprises: pressurizing the liquid to 50 MPa or higher and forming a jet; passing the jet through a microsieve filter, the microsieve filter having a pore size of 0.1 to 1 microns and a thickness of 0.5 to 1.5 microns.

[0031] The method of the present disclosure can be used for various types of applicable liquids, especially liquids containing beneficial bioactive molecules and beneficial heat-sensitive substances in the fields of food, medicine, etc. In the field of food, it can be used for drinkable liquids such as liquid milk, fruit juice, etc. containing various beneficial bioactive molecules and beneficial heat-sensitive substances but requiring strong sterilization. The method of the present disclosure is particularly suitable for liquid milk, especially cow milk. Unlike traditional static high pressure or single high-pressure jet sterilization process, the present disclosure uses high-pressure jet combined with microsieve filtration to process cow milk, ensuring the efficiency of sterilization while also protecting beneficial bioactive molecules such as proteins and fats in the cow milk to achieve a low inactivation rate of the original nutritional components of the cow milk. The present disclosure uses a unique microsieve filter, which separates microorganisms and nutritional components based on the different sizes of microorganisms and various components in cow milk, more accurately separates microorganisms and nutritional components, and achieves a 10 -7 fold reduction in microorganisms without affecting the nutrition or taste of the cow milk. The method of the present disclosure is also suitable for fruit juice, such as freshly squeezed fruit juice.

[0032] The present disclosure uses high-pressure jet for sterilization. In order to achieve sterilization, the liquid needs to be pressurized to 50 MPa or higher to form a jet. If the pressure is too low, the sterilization effect of the jet formed is not obvious.

[0033] The formed jet is directed towards the microsieve filter, thereby passing the liquid through the microsieve filter. Preferably, the jet is directed substantially perpendicular to the filtration face of the microsieve filter, such as within 10°, more preferably within 5°, most preferably perpendicular to the filtration face. The above preferred angle range is advantageous for facilitating the passage of beneficial bioactive molecules having a size smaller than the pore size of the microsieve filter.

[0034] As mentioned above, the presence of the microsieve filter enables a precise and efficient separation of the harmful microorganisms and the beneficial bioactive molecules during the advancement of the jet. Not only that, but the inventors have surprisingly found that, during this process, the ultra-high pressure jet can be somewhat buffered after reaching the microsieve filter, as the pores of the microsieve filter provide an outlet for the fluid along the jet path, compared to the usual ultra-high pressure jet impact against the container wall or against another jet. This enables the release of kinetic energy at a slower speed, which does not affect the killing of the trapped bacteria, but can avoid a sharp temperature rise in the local impact. By properly adjusting the jet pressure, speed, and pore size of the microsieve filter, among other parameters, the temperature rise of the liquid can be controlled to a level that does not significantly damage the beneficial heat-sensitive substances in the liquid. Thus, the ultra-high pressure sterilization method of the present disclosure is also advantageous for preserving the beneficial heat-sensitive substances in the liquid, compared to the conventional ultra-high pressure jet sterilization technique.

[0035] In one embodiment, a microsieve filter having an appropriate pore size and thickness is selected to cooperate with the ultra-high pressure jet. The pore size of the microsieve filter is selected mainly based on the size of the beneficial bioactive molecules to be preserved. The thickness of the microsieve filter is selected not only to ensure its strength under the ultra-high pressure jet, but more importantly to provide a rectification and anti-temperature rise effect on the jet. When the jet passes through the microsieve filter having a suitable thickness, a gradient buffering deceleration is obtained, and the liquid flow becomes a flow with appropriately reduced pressure and speed after passing through the microsieve filter, facilitating subsequent processing. During this process, the liquid flow can also continuously dissipate heat via heat exchange with the microsieve filter wall to maintain a relatively low temperature.

[0036] In one embodiment, the microsieve filter has a pore size of 0.1 to 1 micrometer and a thickness of 0.5 to 1.5 micrometers, to sufficiently separate the microorganisms from the beneficial bioactive molecules, protect the beneficial heat-sensitive substances, and sufficiently gradient-buffer the jet. Preferably, the pore size can be about 0.5 micrometers. Preferably, the microsieve filter thickness can be about 1.0 micrometers. In one embodiment, "about" can refer to a deviation of + / - 10%.

[0037] The method of ultra-high pressure jet sterilization of the liquid in the above embodiments can sufficiently kill the microorganisms in the liquid, while efficiently preserving the beneficial bioactive molecules and the beneficial heat-sensitive substances in the liquid.

[0038] Preferably, the microsieve has a porosity in the range of 75% to 85%, more preferably about 80%. The reason for the preference is that within a certain range, the greater the porosity, the higher the liquid phase volume fraction, the more complete the liquid wetting, the faster the filtration speed, the greater the permeation flux, and the higher the effective separation rate of microorganisms from beneficial bioactive molecules. However, beyond a certain range, as the porosity increases, the available surface area for fluid-membrane interaction also increases, resulting in more interactions and potential flow resistance, affecting the overall efficiency of fluid passing through the microsieve, and at the same time, the porosity affects the fouling behavior, i.e. the accumulation of particles or contaminants on the surface or within its pores. Beyond a certain range of porosity, the surface is more prone to fouling, with more open space for particles to deposit. These factors can instead lead to a decrease in filtration efficiency at excessively high porosity.

[0039] In one embodiment, a suitable microsieve structure is selected, more preferably the microsieve is an anisotropic microsieve. In the microstructure of the microsieve, there are two types of structures, isotropic and anisotropic. The physical structure of the isotropic microsieve is consistent in all directions, and the porosity in all directions is similar. The anisotropic microsieve can have different structures in different directions. For example, it can be a special anisotropic structure, transverse isotropy, i.e. the structure is consistent in the transverse direction, but the structure changes in the longitudinal direction. In one embodiment, an anisotropic microsieve comprises a support layer, a transition layer and a separation layer in sequence in the filtration direction. In this microsieve, each layer plays a different role. Compared to the isotropic structure, the anisotropic structure can take advantage of the high permeation flux of the support layer while taking into account the filtration accuracy of the separation layer, and it is easier to remove contaminants on the surface and within the pores of the membrane by backflushing, reducing the risk of clogging. The transition layer provides a transition from the support layer to the separation layer.

[0040] There is no particular requirement for the cross-sectional shape of the microsieve, as long as it can cooperate with the nozzle to achieve microsieve filtration of the jet liquid. There is also no particular requirement for the hole shape of the microsieve, for example, it can be a round hole, a square hole, etc.

[0041] Preferably, the liquid is pressurized to 50 MPa to 350 MPa. Beyond 350 MPa, the equipment cost and operating cost increase greatly, but the sterilization effect does not improve further significantly. For example, the liquid can be pressurized to 150 MPa to 250 MPa, such as about 200 MPa.

[0042] Preferably, the velocity of the jet leaving the nozzle is in the range of 1000 m / s to 1200 m / s. This range has the advantage of providing a higher kinetic energy, thereby enabling the beneficial ingredients to be pressurized through the microsieve while effectively retaining and killing bacteria, thereby achieving more complete separation of the ingredients.

[0043] Preferably, the temperature of the microsieve is maintained below 55°C. In one embodiment, the temperature of the microsieve can be controlled to be between 45°C and 55°C, for example about 50°C. For a liquid in the general food field, this temperature range can generally ensure that the beneficial heat-sensitive substances in the liquid, such as heat-sensitive flavor substances or nutrients, are not damaged. The temperature can be maintained in this range by adjusting the jet parameters and the microsieve parameters. More preferably, the temperature can be maintained by setting a temperature control device, as described below.

[0044] Preferably, the liquid is liquid milk, more preferably cow milk. Optionally, the cow milk is whole cow milk, partially skimmed cow milk, skimmed cow milk, or formula milk in a uniform state.

[0045] For liquid milk, the liquid milk needs to be pressurized to 200 MPa to 250 MPa. For example, for cow milk, when the ultra-high pressure jet pressure reaches 250 MPa or above, the milk protein structure changes, bitter peptides are precipitated, and the cow milk produces a negative sensory perception for the drinker. Therefore, for liquid milk, the pressure is strictly controlled to be below 250 MPa to ensure both effective sterilization rate and product quality. At the same time, lower ultra-high pressure can make the pressurization process short in time, release pressure quickly, avoid long-term pressure maintenance process, and reduce the denaturation rate of proteins and fats, and increase the retention rate of active proteins. In addition, the jet pressure needs to be above 200 MPa. For liquid milk, when it is below 200 MPa, although a certain degree of sterilization can be achieved, the sterilization effect is poor, resulting in a relatively short shelf life. For example, when the pressure is reduced to below 150 MPa, long-term shelf life tests can not be qualified. Without being bound by any theory, the need for high pressure for liquid milk can be due to two reasons. On the one hand, liquid milk is usually obtained from animal milking, and in this process, air, containers, and transportation, etc. are extremely easy to bring in bacteria, and liquid milk is very nutritious, and bacteria grow fast, resulting in a large amount of bacteria, which requires higher sterilization capacity. On the other hand, liquid milk contains a variety of microorganisms, including about 10% of psychrophilic bacteria, which account for about 10% of the total number of microorganisms. Since liquid milk is usually stored at low temperature, the proportion of psychrophilic bacteria gradually increases, and the pressure required to kill psychrophilic bacteria is usually higher than that required to kill other bacteria.

[0046] Preferably, the method further comprises a pre-treatment before pressurizing the liquid milk, the pre-treatment comprising a milk clarifying and bacteria-removing centrifugal treatment to remove at least part of the macromolecular impurities. The pre-treatment can effectively remove at least part of the impurities, including part of the relatively large bacteria, thus reducing the burden of the ultra-high pressure jet sterilization and reducing the risk of clogging of the microsieve. The milk clarifying and bacteria-removing centrifugal treatment can be used to remove the above-mentioned components, as long as the pre-treatment method does not conflict with the spirit of the present disclosure. The macromolecular impurities are the undesirable components commonly found in liquid milk, which refer to substances with a size greater than 1 micron in the present disclosure. Typically, the macromolecular impurities in the liquid milk include bacteria, fungi (such as yeast and mold, for example, about 2 to 5 microns in size), animal cells (such as bovine cells, for example, about 10 microns in size), animal hair (such as cow hair, for example, greater than 10 microns in size), spores, etc. Preferably, the temperature of the microsieve is maintained at 2°C to 6°C, for example, about 4°C. It is advantageous for the liquid milk to be maintained at a temperature in the range of 2°C to 6°C during processing. Therefore, the liquid milk is also maintained in this range during the microsieve filtration process. The temperature can be maintained by a microsieve temperature control device.

[0047] Preferably, the method further comprises a cooling treatment of the liquid milk before forming the jet, the liquid milk being cooled to 2°C to 6°C. This can make the treated liquid milk always in the ideal low temperature range, which helps to maintain the properties of the liquid milk.

[0048] In one embodiment, the present disclosure provides an apparatus for ultra-high pressure jet sterilization of a liquid, characterized in that the apparatus comprises: an ultra-high pressure jet generating device, the ultra-high pressure jet generating device comprising a pressurizing component for pressurizing the liquid to a pressure of 50 MPa or above and a jet nozzle; and a microsieve towards the jet nozzle, the microsieve having a pore size of 0.1 to 1 micron and a thickness of 0.5 to 1.5 microns. The apparatus can be used to implement the aforementioned method of the present disclosure to produce a liquid, such as liquid milk, particularly cow milk, which is sufficiently sterilized but the beneficial substances are sufficiently preserved.

[0049] Preferably, the apparatus has a microsieve temperature control device. The temperature control device can achieve the aforementioned temperature control. The microsieve temperature control device of the present disclosure is not particularly limited as long as it can control the temperature of the microsieve. The temperature control device can generally include a heat dissipation device, a temperature measuring device, and a control system. The heat dissipation device can be, for example, a heat exchanger equipped with a cooler, etc. Typically, the temperature measuring device measures the temperature of the microsieve and transmits the temperature to the control system, which makes corresponding feedback to control the heat dissipation device, so as to ensure that the temperature of the microsieve is in the required range.

[0050] Preferably, the microsieve comprises one or more of the following materials: synthetic diamond, natural diamond and graphene. These materials are hard enough to resist the strong impact of the ultra-high pressure jet without deformation, and also have good thermal conductivity, which is conducive to heat dissipation. Composite materials containing them can be used to manufacture microsieves.

[0051] Figure 1 is a schematic flow chart of the ultra-high pressure jet sterilization of liquid milk according to one embodiment of the method of the present disclosure, comprising the following steps.

[0052] a. Pretreatment

[0053] The liquid milk is pretreated, comprising milk cleaning and sterilization centrifugation, to remove at least part of the macromolecular impurities such as animal cells, animal hair, spores, fungi and bacteria. The milk cleaning and sterilization centrifugation temperature is 45 to 55°C to maintain the nutrients in the milk. Subsequently, cooling is performed before the jet is generated, with a cooling temperature of 2 to 6°C.

[0054] b. Jet generation

[0055] The liquid milk is subjected to high pressure storage, and then passed through a nozzle to obtain a liquid milk in a high-speed jet state. The pressure reaches 200 MPa to 250 MPa. The speed of the formed jet can reach more than 1000 m / s.

[0056] c. Microsieve filtration

[0057] The liquid milk is subjected to microsieve filtration at 2 to 6°C, more accurately separating microorganisms and nutrients, and releasing kinetic energy by buffering the high-speed jet state through the microsieve. The microsieve has a pore size of 0.1 to 1.0 pm and a thickness of 0.5 to 1.5 pm.

[0058] d. Product generation

[0059] The liquid milk after gradient buffering deceleration and pressure reduction by the microsieve can be subjected to post-treatment, such as maintaining cooling at 2 to 6°C, and further storage.

[0060] Figure 2 is a schematic diagram of one embodiment of the apparatus according to the present disclosure. Liquid from a liquid source reaches a pressurizing device to form liquid with ultra-high pressure, and then reaches a nozzle and is ejected to form a jet. A microsieve is arranged downstream of the nozzle and faces the nozzle. Optionally, a cooling device cools the liquid before the pressurizing device. Optionally, a temperature control device controls the temperature of the microsieve.

[0061] Figure 3 is a schematic diagram of the cooperation of the nozzle and the microsieve of one embodiment of the apparatus according to the present disclosure. In the figure, the correspondence between each reference numeral and the component name is as follows: 1, cavity; 2, nozzle; 3, pipe; 4, microsieve.

[0062] The liquid is pressurized in the chamber 1 and forms a jet through the nozzle 2, which is injected into the pipe 3 and reaches and passes through the microsieve filter 4. By setting the appropriate filter aperture and thickness, and matching the jet pressure, sterilization of the jet and retention of the small molecule active ingredients in the jet at low temperature are achieved.

[0063] Typically, the nozzle diameter ranges from 0.1 to 0.4 mm, and the distance between the nozzle and the microsieve filter is 2 to 10 mm. When the jet pressure is 200 MPa and the jet velocity is 1000 m / s, the processing capacity of this device for liquid milk is 1000 liters / hour.

[0064] The microsieve filter 4 can have a microsieve filter temperature control device (not shown) to maintain the microsieve filter at the desired temperature.

[0065] The following examples are used to illustrate the present disclosure, but are not intended to limit the scope of the present disclosure.

[0066] If a specific technique or condition is not specified in the examples, it is performed according to the technique or condition described in the literature in the art, or according to the product manual. If the manufacturer of the reagent or instrument is not specified, it is a conventional product that can be purchased through a regular channel.

[0067] Example 1. Ultra-high pressure jet sterilization of cow milk with a microsieve filter

[0068] This example provides an ultra-high pressure jet sterilization method with a microsieve filter, which retains the original nutritional ingredients and flavor of cow milk in fresh milk and completely removes microorganisms.

[0069] First step: Pretreatment of cow milk, including milk cleaning and sterilization centrifugation to remove at least part of the macromolecular impurities such as cow cells, cow hair, spores, fungi and bacteria. The milk cleaning and sterilization centrifugation temperature is 50°C. Then cooling is performed before the jet is generated, and the cooling temperature is 6°C.

[0070] Second step: High pressure energy storage is applied to the cow milk, and then the cow milk is passed through a nozzle to obtain a high-speed jet state. The pressure reaches 200 MPa. The velocity of the formed jet is 1000 m / s.

[0071] Third step: The cow milk is filtered by an isotropic microsieve filter at 4°C to more accurately separate microorganisms and nutritional ingredients, and to buffer the high-speed jet state and release kinetic energy through the microsieve filter. The microsieve filter aperture is 0.5 μm, the microsieve filter thickness is 1.0 μm, and the porosity is 75%.

[0072] Fourth step: The liquid milk after gradient buffering, deceleration and pressure reduction by the microsieve filter is subjected to cooling treatment. The cooling temperature is 6°C. After obtaining the product, it is stored at low temperature.

[0073] Example 2 Ultra-high pressure jet sterilization of milk with microsieve filter

[0074] The present example provides an ultra-high pressure jet sterilization method with microsieve filter, which can keep the original nutritional components and flavor of milk in fresh milk and completely remove microorganisms.

[0075] First step: pretreatment of milk, including milk cleaning and sterilization centrifugation, to remove at least part of macromolecular impurities, such as bovine cells, bovine hair, spores, fungi and bacteria. The temperature of milk cleaning and sterilization centrifugation is 50℃. Then cooling is performed before generating jet, and the cooling temperature is 4℃.

[0076] Second step: high pressure storage of the milk, and then passing through a nozzle to obtain high-speed jet state of milk. The jet pressure reaches 200 MPa. The speed of the formed jet is 1100 m / s.

[0077] Third step: isotropic microsieve filter treatment of the milk at 4℃, to more accurately separate microorganisms and nutritional components, and to buffer high-speed jet state and release kinetic energy through the microsieve filter. The microsieve filter has a pore size of 1.0 μm, a thickness of 1.0 μm, and a porosity of 85%.

[0078] Fourth step: cooling treatment of the liquid milk after gradient buffering, deceleration and pressure reduction by the microsieve filter. The cooling temperature is 4℃.

[0079] Example 3 Ultra-high pressure jet sterilization of milk with microsieve filter

[0080] The present example provides an ultra-high pressure jet sterilization method with microsieve filter, which can keep the original nutritional components and flavor of milk in fresh milk and completely remove microorganisms.

[0081] First step: pretreatment of milk, including milk cleaning and sterilization centrifugation, to remove at least part of macromolecular impurities, such as bovine cells, bovine hair, spores, fungi and bacteria. The temperature of milk cleaning and sterilization centrifugation is 50℃. Then cooling is performed before generating jet, and the cooling temperature is 2℃.

[0082] Second step: high pressure storage of the milk, and then passing through a nozzle to obtain high-speed jet state of milk. The jet pressure reaches 250 MPa. The speed of the formed jet is 1200 m / s.

[0083] Third step: anisotropic microsieve filter treatment of the milk at 4℃, to more accurately separate microorganisms and nutritional components, and to buffer high-speed jet state and release kinetic energy through the microsieve filter. The microsieve filter has a pore size of 0.5 μm, a thickness of 1.0 μm, and a porosity of 80%. The anisotropic microsieve filter includes a support layer, a transition layer and a separation layer.

[0084] Fourth step: cooling treatment of the liquid milk after the gradient buffer deceleration pressure reduction through the microsieve filter. The cooling temperature is 2°C.

[0085] Example 4. Ultra-high pressure jet sterilization of milk with microsieve filter

[0086] This example provides an ultra-high pressure jet sterilization method with microsieve filter, which retains the original nutritional ingredients and flavor of milk in fresh milk and completely removes microorganisms.

[0087] First step: pretreatment of milk, including milk cleaning and sterilization centrifugal treatment, to remove at least part of macromolecular impurities such as bovine cells, bovine hair, spores, fungi and bacteria. The milk cleaning and sterilization centrifugal temperature is 50°C. Then cooling treatment is performed before the jet is generated, and the cooling temperature is 6°C.

[0088] Second step: high pressure energy storage is applied to the milk, and then the milk passes through a nozzle to obtain a high-speed jet state of the milk. The pressure reaches 250 MPa. The speed of the formed jet is 1000 m / s.

[0089] Third step: anisotropic microsieve filter treatment at 4°C is applied to the milk to more accurately separate microorganisms and nutritional ingredients, and to buffer the high-speed jet state and release kinetic energy through the microsieve filter. The microsieve filter has a pore size of 1.0 μm, a microsieve filter thickness of 1.0 μm, and a porosity of 80%. The anisotropic microsieve filter includes a support layer, a transition layer and a separation layer.

[0090] Fourth step: cooling treatment of the liquid milk after the gradient buffer deceleration pressure reduction through the microsieve filter. The cooling temperature is 6°C. The product is stored at low temperature after being obtained.

[0091] Example 5. Ultra-high pressure jet sterilization of fresh orange juice with microsieve filter

[0092] This example provides an ultra-high pressure jet sterilization method with microsieve filter, which retains the original nutritional ingredients and flavor of orange in fresh orange juice and completely removes microorganisms.

[0093] First step: pretreatment of fresh orange juice, including crushing, enzyme treatment, clarification and filtration treatment; the temperature of enzyme treatment is 40°C, and the temperature of clarification and filtration is 6°C.

[0094] Second step: high pressure energy storage is applied to the orange juice, and then the orange juice passes through a nozzle to obtain a high-speed jet state of the orange juice. The pressure reaches 150 MPa. The speed of the formed jet is 1000 m / s.

[0095] Third step: The orange juice is filtered using an isotropic microsieve filter at 50°C, more precisely separating the microorganisms and nutrients, and buffering the high-speed jet state and releasing kinetic energy through the microsieve filter. The microsieve filter has a pore size of 0.5 pm, a thickness of 1.0 pm, and a porosity of 75%.

[0096] Fourth step: The orange juice after the gradient buffer deceleration and pressure reduction through the microsieve filter is subjected to cooling treatment. The cooling temperature is 6°C. The product is obtained and stored at low temperature.

[0097] Table 1 Test parameters for Examples 1-5

[0098] Test Example 1

[0099] The target unopened shelf life of the products of Examples 1-5 was measured, and the results are shown in Table 2.

[0100] Table 2 Unopened shelf life (6°C) test analysis

[0101] Test Example 2

[0102] The target opened shelf life of the products of Examples 1-5 was measured, and the results are shown in Table 3.

[0103] Table 3 Opened shelf life (6°C) test analysis

[0104] Test Example 3

[0105] The microbiological indicators of Examples 1-5 were measured, and the results are shown in Table 4.

[0106] Table 4 Microbiological indicators

[0107] Test Example 4

[0108] The nutritional indicators of Examples 1-5 were measured, and the results are shown in Table 5 together with the nutritional indicators of the untreated liquid.

[0109] Table 5 Nutritional indicators

[0110] As can be seen from Examples 1-5 and Test Examples 1-4, the methods of the present disclosure achieve good sterilization and good preservation of beneficial bioactive molecules and beneficial heat-sensitive components, resulting in products that achieve a shelf life of at least 11 days and maintain good flavor. Among the components listed in the tables, examples of beneficial bioactive molecules and heat-sensitive components are lactoferrin, a-lactalbumin, β-lactoglobulin, and Vc.

[0111] In the example of cow milk, the shelf life of Example 2 was slightly worse than Examples 1, 3, and 4. However, the unopened and opened shelf life also reached 11 days and 1 day, respectively. The reason can be that the pressure was relatively low and the mesh size was large, and the treatment of bacteria was not as thorough as the other three examples.

[0112] Comparative Example 1

[0113] On the basis of Example 1, the jet pressure of the second step was adjusted, and 50 MPa, 100 MPa, and 150 MPa were selected for gradient testing: the jet-treated cow milk was subjected to microsieve filtration treatment, and the microsieve filtration aperture was 0.5 μm; the raw material and the remaining steps were the same as in Example 1.

[0114] After detection, the total number of colonies of the finished product increased with the decrease of the jet pressure. The unopened shelf life (6°C) test analysis of the cow milk sample obtained under the treatment conditions of Comparative Example 1 was less than 7 days, and the opened shelf life (6°C) test analysis was less than 1 day. The sample acidity was > 18°, and the overall sensory was unqualified. The alkaline phosphatase was positive, the total number of colonies was 1.0 to 2.0 Lg CFU / mL, and the coliform group was 0.6 to 0.7 Lg CFU / mL.

[0115] Comparative Example 1 shows that for liquid milk, the high-pressure sterilization effect of Example 1 is better. When the pressure is less than 200 MPa, although there is also a sterilization effect, the sterilization effect is slightly worse. The reason for requiring high pressure is as described above, mainly because the amount of bacteria in liquid milk is large and the proportion of psychrophilic bacteria is high. It should be noted that although the experiments using lower pressure are described in this comparative example, it is not intended to indicate that the method of the present disclosure using these pressures is not suitable for liquid milk. When using lower pressure, the sterilization effect is not optimal, but compared with the scheme without a microsieve filter screen at the same low pressure, better retention of nutrients and flavor substances can still be achieved at the same sterilization level.

[0116] Comparative Example 2

[0117] On the basis of Example 2, the microsieve screen aperture of the third step was adjusted, and 2.0 μm and 3.0 μm were selected for gradient testing: the cow milk was subjected to jet treatment, and the jet pressure was 200 MPa; the raw material and the remaining steps were the same as in Example 2.

[0118] After detection, the total number of colonies of the finished product increased with the increase of the microsieve screen aperture. The unopened shelf life (6°C) test analysis of the cow milk sample obtained under the treatment conditions of Comparative Example 2 was less than 3 days, and the opened shelf life (6°C) test analysis was less than 1 day, and slight clots were produced. The sample acidity was > 18°, and the overall sensory was unqualified. The alkaline phosphatase was positive, the total number of colonies was 2.0 to 2.5 Lg CFU / mL, and the coliform group was 1.18 to 1.30 Lg CFU / mL.

[0119] Comparative Example 2 shows that when the pore size of the microsieve filter is outside the range of the present disclosure, a significant amount of microorganisms can pass through the filter without being destroyed, thereby resulting in a shelf life that is not qualified.

[0120] Comparative Example 3

[0121] On the basis of Example 1, the microsieve filtration process was removed, and the milk was subjected to an ultrahigh pressure jet treatment. A pressure of 200 MPa was selected for testing. The raw material and the remaining steps were the same as in Example 1, but the jet was directed at the pipe / container wall.

[0122] It was detected that the total number of colonies of the finished product increased compared to Example 1. The milk sample obtained under the treatment conditions of Comparative Example 3 was tested and analyzed for unopened shelf life (6°C) for 7 days and opened shelf life (6°C) for 1 day. The acidity of the sample was greater than 18° during the shelf life, and the overall sensory quality at the end of the shelf life was unqualified, with a decrease in milk aroma, and the appearance of off-flavors such as acid odor and halitosis. The alkaline phosphatase was negative. This shows that the sterilization effect of the jet directed at the wall is also poor. In particular, more of the milk peroxidase, lactoferrin, lactalbumin, and lactoglobulin, which are nutrients, were destroyed compared to Example 1, resulting in a decrease in product quality.

[0123] Table 6 Nutrient indicators

[0124] As can be seen from the examples and comparative examples, the milk produced using the device of the present disclosure according to the method of the present disclosure has an excellent shelf life, stable composition, and better preservation of nutrients and flavor.

[0125] The present disclosure uses ultrahigh pressure jet to perform pressure jet treatment on liquid milk, and then performs microsieve filter treatment. This solves the problem of low retention rate of active substances and low microbial kill rate when using ultrahigh pressure sterilization alone. The microsieve technology not only accurately separates microorganisms and small-molecule nutrients to further improve the overall sterilization efficiency, but also slowly releases kinetic energy through the buffer high-speed jet state, avoiding the instantaneous conversion of kinetic energy into heat energy, and simultaneously reducing the loss of active nutrients. The sterilization effect of ordinary ultrahigh pressure jet on liquid milk is at most 99.99%, while the method of the present disclosure can improve the sterilization effect to 99.99999%, and compared to conventional ultrahigh pressure sterilization, more active nutrients are retained, improving product quality. The present disclosure is a high-efficiency and simple sterilization method suitable for liquid milk containing heat-sensitive components, which can completely kill microorganisms, retain the active nutrients of liquid milk, and at the same time retain the flavor, color, and taste of the product.

[0126] Although the present disclosure has been described in detail with particular reference to illustrative embodiments thereof, it should be understood that variations and modifications of the disclosed embodiments exist within the scope of the present disclosure as defined by the appended claims.

Claims

1. A method of ultra-high pressure jet sterilization of a liquid, characterized in that, The method comprises: pressurizing the liquid to 50 MPa or more and forming a jet stream; passing the jet stream through a microsieve filter having a pore size of 0.1 to 1 micrometers and a thickness of 0.5 to 1.5 micrometers.

2. The method of claim 1, wherein, The microsieve filter has a porosity in the range of 75% to 85%.

3. The method of claim 1, wherein, The microsieve filter is an anisotropic microsieve filter.

4. The method of claim 1, wherein, The liquid is pressurized to 50 MPa to 350 MPa.

5. The method of claim 1, wherein, The temperature of the microsieve filter is maintained at 55°C or less.

6. The method of claim 1, wherein, The liquid is liquid milk, wherein the liquid milk is pressurized to 200 MPa to 250 MPa to form the jet stream.

7. The method of claim 6, wherein, The method further comprises a pretreatment before pressurizing the liquid milk, the pretreatment comprising a clean milk and a sterilization centrifugal treatment to remove at least part of macromolecular impurities.

8. The method of claim 6, wherein, The temperature of the microsieve filter is maintained at 2°C to 6°C.

9. The method of claim 6, wherein, The method further comprises a cooling treatment of the liquid milk before forming the jet stream, the liquid milk being cooled to 2°C to 6°C.

10. The method of claim 6, wherein, The liquid milk is cow milk.

11. An apparatus for ultra-high pressure jet sterilization of a liquid for use in the method of claim 1, characterized in that, The apparatus comprises: an ultra-high pressure jet stream generating device comprising a pressurizing member to pressurize a liquid to 50 MPa or more and a jet stream nozzle; and a microsieve filter toward the jet stream nozzle, the microsieve filter having a pore size of 0.1 to 1 micrometers and a thickness of 0.5 to 1.5 micrometers.

12. The apparatus of claim 11, wherein, The microsieve filter has a porosity in the range of 75% to 85%.

13. The apparatus of claim 11, wherein, The microsieve filter is an anisotropic microsieve filter.

14. The apparatus of claim 11, wherein, The apparatus has a microsieve filter temperature control device.

15. The apparatus of claim 11, wherein, The microsieve filter comprises one or more of the following materials: synthetic diamond, natural diamond, and graphene.

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