CN112167337A - Ultraviolet sterilization method and sterilization machine for producing high-activity liquid milk - Google Patents
Ultraviolet sterilization method and sterilization machine for producing high-activity liquid milk Download PDFInfo
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- 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
- A23C3/02—Preservation of milk or milk preparations by heating
- A23C3/03—Preservation of milk or milk preparations by heating the materials being loose unpacked
- A23C3/033—Preservation of milk or milk preparations by heating the materials being loose unpacked and progressively transported through the apparatus
-
- 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
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- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Food Science & Technology (AREA)
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- Health & Medical Sciences (AREA)
- Toxicology (AREA)
- Apparatus For Disinfection Or Sterilisation (AREA)
- Dairy Products (AREA)
Abstract
The invention discloses an ultraviolet sterilization method and a sterilization machine for producing high-activity liquid milk, and belongs to the technical field of food processing. The ultraviolet sterilization component 15 of the ultraviolet sterilization machine comprises a gasket 1, an ultraviolet intensity monitor 2, a three-way valve 3, a PFA pipe 4, an ultraviolet lamp tube 5, a quartz sleeve 6 and a PFA pipe fixing clamp 7. The invention adopts the spiral surrounding form of the PFA pipe 4, controls the D/Dc range to be 0.03-0.1, changes the flow rate of liquid milk or the running length of milk in the PFA pipe 4, changes the processing amount of milk by changing the number of ultraviolet lamp tubes connected in parallel, has convenient operation and less time consumption, can meet various processing requirements and has wide application.
Description
Technical Field
The invention relates to an ultraviolet sterilization method and a sterilization machine for producing high-activity liquid milk, belonging to the technical field of food processing.
Background
Ultraviolet sterilization is a novel non-thermal sterilization mode. The ultraviolet (UV-C) wavelength band for sterilization is typically 200 and 280nm, with 253.7nm being most preferred. Ultraviolet light kills bacteria, viruses, fungi and other microorganisms by destroying their DNA and thereby killing them. Ultraviolet sterilization is mainly applied to three fields: air sterilization, liquid sterilization and surface sterilization. In the food industry, for liquid sterilization, clear liquids such as water, egg liquid, fruit juice, and wine have been used. Because of the poor penetration of turbid liquids by uv light, the materials currently available for uv sterilization are limited primarily to clear liquids.
The cow milk is rich in nutrient components and plays an important role in human growth and health. Cow milk is rich in proteins, vitamins, minerals, etc., and besides, cow milk is rich in bioactive proteins including immunity proteins and antibacterial enzymes. The active proteins have protective effect on human intestinal health and immune system. Most of the bioactive proteins are heat-sensitive proteins and are extremely easy to inactivate in the heat sterilization process of the cow milk. Therefore, the ultraviolet sterilization has good application prospect in the aspect of cow milk sterilization as a mature non-thermal sterilization technology. Although the ultraviolet sterilization temperature is low and the efficiency is high, the ultraviolet penetration rate is reduced due to the high turbidity of the milk, and the sterilization effect is greatly weakened.
At present, researchers have invented several ultraviolet sterilization methods and devices aiming at different liquid foods. Sunyiwei (201811149112.8) discloses a drinking water ultraviolet sterilization method, which adopts the irradiation sterilization inside a water pipe and uses a ladder-shaped sterilization channel, thereby increasing the ultraviolet treatment time of water flow and improving the ultraviolet sterilization efficiency; however, since the milk is turbid liquid, although the ladder-shaped channel can play a certain shunting effect, the ultraviolet lamps are respectively arranged at the two ends of the device, and the sterilization effect cannot be guaranteed due to uneven milk contact with ultraviolet rays. The great forest male (201680016968.0) discloses a UV-C water purification device, improves a UV-C LED module, reduces the loss of ultraviolet light in propagation, and improves the light extraction efficiency; however, the material container is a water tank, the UV-C module is arranged in the water tank, the material depth is large, the material container is in a static state, and the sterilization process is discontinuous. Sunfu (201220341807.8) discloses an ultraviolet ray beverage sterilization device, which mainly comprises a container for containing beverage and an ultraviolet ray lamp tube inside, wherein materials enter from the top of the container and flow out from the bottom; the microwave generator is adopted to generate microwave excitation ultraviolet rays, so that the ultraviolet intensity and the sterilization effect are improved, and the service life of the ultraviolet lamp is prolonged; however, because the peripheral space of the ultraviolet lamp tube in the container is larger, the liquid layer is thicker when the materials flow in the container, and ultraviolet rays are difficult to completely penetrate turbid liquid; the materials flow in and out perpendicular to the ultraviolet lamp tube, the direction of the materials is perpendicular to the direction of the ultraviolet lamp tube, and the flowing mode of the liquid is difficult to control when the materials flow; therefore, the device can not ensure that the turbid materials are uniformly irradiated by ultraviolet rays. Yi Quan (201720671599.0) discloses an ultraviolet sterilizer for beverage production, wherein a plurality of ultraviolet lamps are arranged in a long cylinder body and are vertical to the direction of a cavity, and a material inlet and a material outlet are both arranged at the top of the cavity; the inner space of the cylinder is large, and a drainage device is not arranged, so that the flowing state of the material is difficult to control; a plurality of ultraviolet lamp tubes are arranged in the cylinder body, and the actual ultraviolet dose received by the material is difficult to calculate. Equestrian mart (201710865815.X) discloses an ultraviolet sterilization device for donkey milk processing, which comprises a sterilization box and a storage box. The sterilizing box adopts heat sterilization, and the ultraviolet lamp tube is arranged in the storage box. During heat sterilization, if the temperature of the sterilization box exceeds a set value, namely the sterilization box breaks down, donkey milk in the sterilization box can be automatically discharged into the storage box, and the donkey milk is continuously sterilized by ultraviolet rays; the ultraviolet light in the device only plays the roles of standby and auxiliary sterilization, and the materials are not uniformly contacted with the ultraviolet light in the storage box, so that the sterilization efficiency is very low.
Therefore, the existing ultraviolet sterilization mode and equipment for liquid food are not suitable for milk sterilization. Therefore, there is a need for an ultraviolet sterilization method capable of sterilizing turbid milk liquid and retaining active ingredients, and the ultraviolet sterilization apparatus has excellent sterilization effect, can continuously process, and can adjust the ultraviolet dosage, the output and the processing temperature.
Disclosure of Invention
In order to solve at least one of the above problems, the present invention provides an ultraviolet sterilization method and a sterilizer for producing high-activity liquid milk.
The invention provides an ultraviolet sterilization machine for producing high-activity liquid milk, which comprises an ultraviolet sterilization component 15, wherein the ultraviolet sterilization component 15 comprises a gasket 1, an ultraviolet intensity monitor 2, a three-way valve 3, a PFA pipe 4, an ultraviolet lamp tube 5, a quartz sleeve 6 and a PFA pipe fixing clamp 7, wherein the surface of the ultraviolet lamp tube 5 is covered with the quartz sleeve 6, the PFA pipe 4 is tightly wound around the quartz sleeve 6 and is fixed by the PFA pipe fixing clamp 7, no gap exists between the PFA pipe 4 and the quartz sleeve 6, each winding of 1m (10-30 circles) of the PFA pipe 4 serves as a sterilization area, and the PFA pipes 4 in adjacent sterilization areas are connected by the three-way valve 3; a gasket 1 is arranged between the ultraviolet lamp tube 5 and the quartz sleeve 6; the ultraviolet intensity detector 2 is closely attached to the outside of the quartz sleeve 6 where the PFA tube is not wound.
In one embodiment of the present invention, one or more ultraviolet intensity detectors 2 are included between adjacent sterilization zones in the ultraviolet sterilization machine.
In one embodiment of the present invention, the uv sterilizer is provided with a feed pump 8 at one side, the PFA tube 4 is passed through the feed pump 8 at one end, and the liquid milk is fed into the pipeline by the feed pump 8.
In one embodiment of the invention, the UV sterilizer is provided with a feed pump 8 on one side and a console 9 on the other side.
In an embodiment of the present invention, the ultraviolet sterilizer further includes a lamp holder 10 and an ultraviolet lamp support 11, and the lamp holder 10 and the ultraviolet lamp support 11 are used for fixing the ultraviolet lamp tube 5.
In an embodiment of the invention, the ultraviolet sterilization machine further comprises a shell bracket 12, a stainless steel shell 13; the stainless steel housing 13 is supported by the housing bracket 12; a plurality of ultraviolet light tubes 5 are contained within a stainless steel housing 13.
In an embodiment of the present invention, the ultraviolet sterilizer further includes a partition 14, and the partition 14 separates each ultraviolet lamp tube 5, so as to ensure that ultraviolet lights emitted by different lamp tubes do not interfere with each other.
In one embodiment of the present invention, the uv sterilizer further comprises a splitter 16, wherein the splitter 16 is arranged between the feeding pump 8 and the stainless steel casing 13; the flow divider 16 divides the raw material equally into each PFA tube 4 in terms of flow rate.
In one embodiment of the present invention, the uv sterilizer further comprises a heating pipe 17, wherein the heating pipe 17 is arranged around the PFA pipe 4 between the feeding pump 8 and the stainless steel casing 13, and is used for heating the material to a certain temperature for subsequent uv sterilization.
In one embodiment of the present invention, the number of the uv sterilization members 15 in the uv sterilization device may be 1 to 100, and correspondingly, the number of the heating pipes 17 and the diverter 16 may be 1 to 10; when the number of the ultraviolet sterilization components is multiple, the ultraviolet sterilization components are placed in parallel, and the treatment capacity of the ultraviolet sterilization machine can be 3-1200L/h.
In one embodiment of the present invention, the uv sterilizer further comprises a console 9, wherein the console 9 can control the temperature inside the uv lamp 5, the uv intensity monitors 2, the feed pump 8, the heating pipe 17 and the stainless steel housing 13, and display the uv intensity monitored by each uv intensity monitor.
In one embodiment of the present invention, the ultraviolet sterilizer comprises an ultraviolet sterilizing member 15, a feed pump 8, a console 9, a lamp tube holder 10, an ultraviolet lamp support 11, a housing support 12, a stainless steel housing 13, a partition plate 14, a flow divider 16 and a heating tube 17, wherein the ultraviolet sterilizing member 15 comprises a gasket 1, an ultraviolet intensity monitor 2, a three-way valve 3, a PFA tube 4, an ultraviolet lamp tube 5, a quartz sleeve 6 and a PFA tube fixing clamp 7; wherein the stainless steel housing 13 is supported by the housing bracket 12; the stainless steel shell 13 contains a plurality of ultraviolet lamp tubes 5, the ultraviolet lamp tubes 5 are separated by partition plates 14, and the ultraviolet lamp tubes 5 are fixed by a lamp tube fixing device 10 and an ultraviolet lamp bracket 11; the ultraviolet lamp tube 5 is covered with a quartz sleeve 6 on the surface, a layer of gasket 1 is arranged between the ultraviolet lamp tube 5 and the quartz sleeve 6, a PFA tube 4 is tightly wound around the quartz sleeve 6, no gap exists between the PFA tube 4 and the quartz sleeve 6, the PFA tube 4 is wound for 10-30 circles to serve as a sterilization area, the whole sterilization area is fixed by a PFA tube fixing clamp 7, and the PFA tubes 4 of adjacent sterilization areas are connected by a three-way valve 3; the ultraviolet intensity detector 2 is tightly attached to the outer side of the quartz sleeve 6 where the PFA tube is not wound; one side of the ultraviolet sterilization machine is provided with a feeding pump 8, and the other side is provided with a console 9; a heating pipe 17 is arranged around the PFA pipe 4 between the feeding pump 8 and the stainless steel shell 13; a splitter 16 is between the feed pump 8 and the stainless steel housing 13.
In an embodiment of the present invention, the outer diameter of the quartz sleeve 6 is 2-3cm, and may be further preferably 2.3cm, and the quartz sleeve is supported and fixed by two stainless steel brackets to ensure that the ultraviolet lamp tube and the quartz sleeve are coaxial.
In one embodiment of the present invention, during the operation process, the liquid milk enters one end of the PFA tube 4 through the feeding pump 8, flows around the inside of the PFA tube for several weeks, flows out from the other end of the PFA tube 4 after receiving the ultraviolet irradiation, and the flow direction of the liquid milk in the PFA tube 4 can be changed by controlling the opening and closing of the three-way valve 3, so that the liquid milk enters the next area to continue the ultraviolet sterilization, or finishes the sterilization and directly flows out.
In one embodiment of the present invention, the stainless steel housing 13 is tightly sealed, and a temperature control system is provided inside, so that the temperature of the uv sterilization module can be controlled between 0-80 ℃ by water bath.
In one embodiment of the present invention, the stainless steel housing 13 has a plurality of metal slots therein for fixing the PFA tube 4 wound around the quartz sleeve.
In one embodiment of the invention, the PFA tube 4 specifications are: the inner diameter is 1-2mm, and the outer diameter is 2-3 mm; more preferably: 1mm by 2mm, 1.5mm by 2mm or 2mm by 3mm (inner diameter x outer diameter).
In an embodiment of the present invention, a ratio of a surrounding inner diameter Dc of the PFA tube 4 to an inner diameter D of the PFA tube 4 in the ultraviolet sterilization apparatus is between 0.03 and 0.1, so that the liquid milk can be uniformly mixed in the tube at different flow rates, and the liquid milk has a good ultraviolet sterilization effect at different treatment amounts.
A second object of the present invention is to provide a method for producing highly active liquid milk using the sterilizer of the present invention.
In one embodiment of the present invention, the PFA tube 4 in the sterilizer is specified as follows: the inner diameter is 1-2mm, and the outer diameter is 2-3 mm; more preferably: 1mm by 2mm, 1.5mm by 2mm or 2mm by 3mm (inner diameter x outer diameter).
In one embodiment of the present invention, the liquid milk is cow's milk or goat's milk.
In one embodiment of the invention, the ratio of the surrounding inner diameter Dc of the PFA tube 4 in the ultraviolet sterilization device to the inner diameter D of the PFA tube 4 is between 0.03 and 0.1, so that the liquid milk can be uniformly mixed in the tube at different flow rates, and the liquid milk has good ultraviolet sterilization effect at different treatment amounts; reynolds number (R) was calculated from the following formulas (1) and (2)e) And dean number (D)e)：
Wherein rho is the density of the liquid milk and is 1021.46kg/m2(ii) a Mu is dynamic viscosity of liquid milk, 1.941X 103Ns/m2(ii) a v is the flow rate of the liquid milk in the tube; d is the inner diameter of the PFA tube 4; dc is the PFA tube 4 surrounding the inner diameter.
Re < 2100 denotes a laminar flow state, Re > 4000 denotes a turbulent flow state, and Re is between them, which denotes a mixed flow state. De is the characterization of the flowing mode of the fluid in the coil, when the D/Dc is more than 0.03 and less than 0.1, the fluid in the coil generates secondary flow pits, and the mixing degree of the fluid can be enhanced.
In one embodiment of the invention, the ultraviolet dose of the liquid milk is changed by changing the flow rate of the liquid milk or the length of the PFA pipe 4 actually used, so that the microorganisms in the liquid milk reach the pasteurization requirement and the bioactive proteins in the liquid milk are ensured not to be significantly reduced; the treatment capacity can be changed by changing the number of the ultraviolet lamp tubes connected in parallel.
In one embodiment of the invention, the high-activity liquid milk refers to liquid milk which has been subjected to a certain sterilization mode, has the microbial limit meeting the national standards of pasteurized milk (GB 19645-2010 and GB 19301-2010), can be stored and sold as pasteurized milk, and has higher content of bioactive proteins such as bioactive proteins of immune activity protein and antibacterial enzyme.
In one embodiment of the invention, the ultraviolet sterilization intensity can be controlled by changing the flow rate of the liquid milk; the flow rate of the selected liquid milk is 50-200 mL/min; specifically, fresh liquid milk is taken, the temperature of the liquid milk is kept at 25 ℃, the liquid milk passes through 5 sterilization areas, the flow rate of the liquid milk in a tube is respectively controlled to be 50-200mL/min, and the corresponding ultraviolet dose is 65-16mJ/cm2。
In one embodiment of the present invention, the bactericidal strength may be controlled by varying the length of the PFA tube 4; selecting 2-6 sterilization zones, each zone having 12 windings (each of PFA4 is 1m in length); specifically, fresh liquid milk is taken, the temperature of the liquid milk is kept at 25 ℃, the liquid milk passes through 2-6 sterilization areas by controlling the opening and closing of a three-way valve 3, and the corresponding ultraviolet dose is 16-47mJ/cm2。
In one embodiment of the invention, the throughput of the highly active liquid milk can be adjusted by changing the number of uv sterilizing members 15 connected in parallel; because the appropriate treatment capacity of each ultraviolet lamp tube is 50-200mL/min, the number of the ultraviolet sterilization components 15 can be 1-100, and correspondingly, the number of the heating tubes 17 and the shunts 16 can be 1-10; when the number of the ultraviolet sterilization components 15 is multiple, the ultraviolet sterilization components are placed in parallel, and the treatment capacity of the ultraviolet sterilization machine can be 3-1200L/h.
In one embodiment of the invention, the flow rate of the liquid milk in the PFA tube 4 of the ultraviolet sterilizer is 50-200 mL/min.
In one embodiment of the present invention, the number of sterilization zones through which the liquid milk passes is 2 to 6, the number of windings of the PFA tube in each sterilization zone is 12, and the length of each winding of the PFA tube is 1 m.
In one embodiment of the invention, the liquid milk may be heated to a certain temperature by a heating pipe before being subjected to ultraviolet irradiation; during ultraviolet sterilization, the liquid milk can be kept at a certain temperature by a temperature control system, and the adjustable temperature range is 0-80 ℃.
The third object of the invention is the high activity liquid milk produced by the method of the invention.
In an embodiment of the present invention, the high-activity liquid milk is one of skim milk, whole milk, skim goat milk, and whole goat milk.
The invention has the beneficial effects that:
(1) the invention provides an ultraviolet sterilizer for producing high-activity liquid milk, which realizes sterilization of turbid liquid of the liquid milk by ultraviolet rays. According to the invention, the PFA pipe 4 is spirally wound, and the D/Dc range is controlled to be 0.03-0.1, so that the liquid milk is fully mixed when running in the pipe, and the sterilization efficiency of the liquid milk is improved; the ultraviolet dose received by the milk is changed by changing the flow rate of the liquid milk or the running length of the liquid milk in the PFA pipe 4, so that the sterilization strength of the liquid milk is controlled; the invention changes the treatment capacity of the liquid milk by changing the number of the ultraviolet lamp tubes connected in parallel, has convenient operation and less time consumption, can meet various treatment requirements and has wide application.
(2) The invention provides an ultraviolet sterilization method for producing high-activity liquid milk, and the method for changing the ultraviolet dosage is various, convenient and quick. The ultraviolet sterilization method can ensure that the microbial quantity of the liquid milk reaches the requirement of national standard, and meanwhile, the damage to the active protein in the liquid milk is obviously lower than that of pasteurization (15 s at 72 ℃) with the weakest heat treatment intensity, and the obvious loss of the active protein is hardly caused.
(3) The invention provides high-activity liquid milk. Compared with pasteurization (72 deg.C for 15s), the high activity liquid milk produced by the method has the same safety, but has more immunocompetent protein and antibacterial protein, and is high activity pasteurized liquid milk.
(4) IgG, IgM, IgA and lactoferrin in cow's milk are collectively called as immunologically active proteins, and have antibacterial, defensive, anti-inflammatory, antioxidant, anticancer and immunoregulatory functions. In addition, both LPO and XO enzymes have antibacterial activity and are beneficial enzymes in milk. The retention of these bioactive proteins has important promotion effects on human intestinal health and immune function. The ultraviolet dose is changed by changing the flow rate of the liquid milk or the actual using length of the PFA tube 4, and the high-activity liquid milk is obtained. After the liquid milk is subjected to ultraviolet sterilization, the total number of colonies is 0-40000CFU/mL, the number of coliform groups is 0CFU/mL, and the total number is in the range of national standards (GB 19645-2010, GB 19301-2010). The contents or activities of bioactive proteins and antibacterial enzymes in the sterilized cow milk, including IgG, IgM, IgA, lactoferrin, peroxidase and xanthine oxidase, are not obviously reduced compared with those before sterilization (and are reduced by 20-60% by pasteurization), and the cow milk is high-activity liquid milk. The ultraviolet sterilization intensity can be adjusted according to the sanitary quality of the raw milk.
Drawings
Fig. 1 shows the structure of an ultraviolet sterilizing member 15 inside an ultraviolet sterilizer;
FIG. 2 is a front view (perspective) of the UV sterilizer;
FIG. 3 is a left side view (perspective) of the UV sterilizer;
FIG. 4 is a top view (perspective) of the UV sterilizer;
in fig. 1-4, a gasket 1, an ultraviolet intensity monitor 2, a three-way valve 3, a PFA tube 4, an ultraviolet lamp tube 5, a quartz sleeve 6, a PFA tube fixing clamp 7, a feeding pump 8, a console 9, a lamp tube holder 10, an ultraviolet lamp holder 11, a housing holder 12, a stainless steel housing 13, a partition plate 14, an ultraviolet sterilization member 15, a splitter 16, and a heating tube 17.
FIG. 5 is a graph of the effect of two UV doses on the amount of immunologically active protein in cow's milk in example 6; wherein a is the effect on IgG content; b is the effect on lactoferrin content; c is the effect on IgM content; d is the effect on IgA content.
FIG. 6 is a graph showing the effect of two UV doses on the levels of bovine Lactoperoxidase (LPO) and Xanthine Oxidase (XO) in example 6.
Detailed Description
The following description of the preferred embodiments of the present invention is provided for the purpose of better illustrating the invention and is not intended to limit the invention thereto.
And (3) total colony count determination: adopting a colony count test piece (6406) of 3M company, taking 1mL of diluted sample, dropwise adding the diluted sample into the center of the test piece, compressing an upper layer film, standing for 1 minute, placing the test piece in an incubator at 32 ℃ for culturing for 24 hours after a culture medium is solidified, and taking the test piece with the colony count of 25-250 for counting.
And (3) determining coliform bacteria: adopting a test piece (6416) for the total number of colonies from 3M company, taking 1mL of diluted sample, dropwise adding the diluted sample into the center of the test piece, compressing an upper layer film, standing for 1 minute, placing the test piece in an incubator at 32 ℃ for culturing for 12 hours after a culture medium is solidified, and taking the test piece with the colony number of 15-150 for counting.
And (3) total spore number determination: taking a certain amount of treated milk, placing in a sterile centrifuge tube, and placing in a water bath kettle at 80 deg.C for 10 min. And immediately placing the mixture in crushed ice for cooling after the heat preservation is finished, taking a proper amount of milk, diluting the milk by a certain multiple, and then carrying out subsequent determination according to a determination method of the total number of colonies.
Determination of the content of immune active proteins (IgG, IgM, IgA, lactoferrin): the IgG, IgM, IgA and lactoferrin content in cow's milk was determined using Elisa kit (Cat. No. E10-118, E10-131, E10-101 and E10-126; Bethy Laboratories, USA). The cow milk is diluted by 500 times and 1000 times for determination, and the standard curve is fitted and quantified by a 4-parameter equation.
Lactoperoxidase (LPO) activity assay: the activity is determined by measuring the rate of a Red fluorescent oxidation product (9-hydroxy-3-isophenoxazolone) generated by the oxidation reaction of the Amplex Red dye (AR) catalyzed by lactoperoxidase. A reaction reagent was prepared by mixing 23.1. mu.L of AR, 4.6. mu.L of a potassium thiocyanate solution and 972.3. mu.L of 100mM phosphate buffer (pH 7.4), 30. mu.L of diluted cow's milk was mixed with 195. mu.L of the reaction reagent, 50. mu.L of the mixed solution was added to a 96-well plate, after incubation at 37 ℃ for 20min, 50. mu.L of 110. mu.M hydrogen peroxide solution was automatically added to the mixture by a microplate reader (50. mu.L of deionized water was used instead of the hydrogen peroxide solution for the blank), and the fluorescence intensity was measured every 10s at an excitation/emission wavelength of 544/590 nm. Standard curves were prepared with different concentration gradients of hydrogen peroxide solution. Lactoperoxidase activity was calculated by the following formula (3):
note that F1 and F2 are the difference between the fluorescence intensities of the two endpoints in T time, and K is the slope of the standard curve.
Xanthine Oxidase (XO) activity assay: xanthine oxidase catalyzes hypoxanthine to produce hydrogen peroxide, which can be catalyzed by horseradish peroxidase (HRP) to produce fluorescent products. The reaction reagent was prepared by mixing 10. mu.L of 10mM AR, 4. mu.L of 200U/mL HRP, 40. mu.L of 10mM hypoxanthine, and 946. mu.L of phosphate buffer (pH 7.4). Adding 50 μ L diluted cow milk into 96-well plate, adding 50 μ L xanthine oxidase reaction reagent, mixing, and measuring fluorescence intensity at excitation/emission wavelength of 544/590nm every 30s with enzyme-labeling instrument. Standard curves were prepared with different concentration gradients of hydrogen peroxide solution. Xanthine oxidase activity was calculated by the following formula (4):
note that F1 and F2 are the difference between the fluorescence intensities of the two endpoints in T time, and K is the slope of the standard curve.
Example 1 ultraviolet sterilizer (an ultraviolet sterilizing means 15)
The ultraviolet sterilization machine comprises an ultraviolet sterilization component 15, a feeding pump 8, a console 9, a lamp tube fixer 10, an ultraviolet lamp bracket 11, a shell bracket 12 and a stainless steel shell 13, wherein the ultraviolet sterilization component 15 comprises a gasket 1, an ultraviolet intensity monitor 2, a three-way valve 3, a PFA tube 4, an ultraviolet lamp tube 5, a quartz sleeve 6 and a PFA tube fixing clamp 7; wherein the stainless steel housing 13 is supported by the housing bracket 12; the stainless steel shell 13 contains 1 ultraviolet lamp tube 5, and the ultraviolet lamp tube 5 is fixed by a lamp tube fixer 10 and an ultraviolet lamp bracket 11; the ultraviolet lamp tube 5 is covered with a quartz sleeve 6 on the surface, a layer of gasket 1 is arranged between the ultraviolet lamp tube 5 and the quartz sleeve 6, a PFA tube 4 is tightly wound around the quartz sleeve 6, no gap exists between the PFA tube 4 and the quartz sleeve 6, the PFA tube 4 is wound for 10-30 circles to serve as a sterilization area, the whole sterilization area is fixed by a PFA tube fixing clamp 7, and the PFA tubes 4 of adjacent sterilization areas are connected by a three-way valve 3; the ultraviolet intensity detector 2 is tightly attached to the outer side of the quartz sleeve 6 where the PFA tube is not wound; one side of the ultraviolet sterilizer is provided with a feeding pump 8, and the other side is provided with a console 9.
In the operation process, the liquid milk enters one end of the PFA pipe 4 through the feeding pump 8, flows around the pipe for a plurality of weeks, flows out of the other end of the PFA pipe 4 after being irradiated by ultraviolet light, and can change the flow direction of the liquid milk in the PFA pipe 4 by controlling the opening and closing of the three-way valve 3, so that the liquid milk enters the next area to continue ultraviolet sterilization or finishes sterilization and directly flows out. The ultraviolet intensity detector 2 is tightly attached to the outer side of the quartz sleeve, and can accurately monitor the ultraviolet intensity measured outside the quartz sleeve. The stainless steel shell 13 is strictly sealed, the temperature control system is arranged in the stainless steel shell, and the temperature (0-80 ℃) of the ultraviolet sterilization module can be controlled through water bath. The console 9 can control the temperature within the ultraviolet lamps, ultraviolet intensity monitors, and stainless steel housing 13. The number of the ultraviolet lamp tubes connected in parallel can be selected by controlling the feed pump 8, so that the treatment capacity of ultraviolet sterilization is changed.
EXAMPLE 2 ultraviolet sterilizer (multiple parallel ultraviolet sterilizing units 15)
The front view, the top view, the side view and the schematic diagram of the internal ultraviolet sterilization module of the ultraviolet sterilization machine are respectively shown in fig. 1, fig. 2, fig. 3 and fig. 4. The ultraviolet sterilization component 15 of the ultraviolet sterilization machine comprises a gasket 1, an ultraviolet intensity monitor 2, a three-way valve 3, a PFA pipe 4, an ultraviolet lamp tube 5, a quartz sleeve 6 and a PFA pipe fixing clamp 7; wherein the stainless steel housing 13 is supported by the housing bracket 12; the stainless steel shell 13 contains a plurality of ultraviolet lamp tubes 5, the ultraviolet lamp tubes 5 are separated by partition plates 14, and the ultraviolet lamp tubes 5 are fixed by a lamp tube fixing device 10 and an ultraviolet lamp bracket 11; the ultraviolet lamp tube 5 is covered with a quartz sleeve 6 on the surface, a layer of gasket 1 is arranged between the ultraviolet lamp tube 5 and the quartz sleeve 6, a PFA tube 4 is tightly wound around the quartz sleeve 6, no gap exists between the PFA tube 4 and the quartz sleeve 6, the PFA tube 4 is wound for 10-30 circles to serve as a sterilization area, the whole sterilization area is fixed by a PFA tube fixing clamp 7, and the PFA tubes 4 of adjacent sterilization areas are connected by a three-way valve 3; the ultraviolet intensity detector 2 is tightly attached to the outer side of the quartz sleeve 6 where the PFA tube is not wound; one side of the ultraviolet sterilization machine is provided with a feeding pump 8, and the other side is provided with a console 9; a heating pipe 17 is arranged around the PFA pipe 4 between the feeding pump 8 and the stainless steel shell 13; a splitter 16 is between the feed pump 8 and the stainless steel housing 13.
In the operation process, after passing through the feeding pump 8, the liquid milk enters one end of the PFA pipe 4 through the heating pipe 17 and the flow divider 16, flows around the pipe for a plurality of weeks, flows out from the other end of the PFA pipe 4 after being irradiated by ultraviolet light, and can change the flow direction of the liquid milk in the PFA pipe 4 by controlling the opening and closing of the three-way valve 3, so that the liquid milk enters the next area to continue ultraviolet sterilization or finishes sterilization and directly flows out. The ultraviolet intensity detector 2 is tightly attached to the outer side of the quartz sleeve, and can accurately monitor the ultraviolet intensity measured outside the quartz sleeve. The stainless steel shell 13 is strictly sealed, the temperature control system is arranged in the stainless steel shell, and the temperature (0-80 ℃) of the ultraviolet sterilization module can be controlled through water bath. The console 9 can control the temperature in the ultraviolet lamp tube 5, the ultraviolet intensity monitor 2, the feed pump 8, the heating tube 17 and the stainless steel shell 13. The shunt 16 can be connected with ten PFA tubes 4 at most simultaneously, and the number of the ultraviolet lamp tubes connected in parallel can be selected by controlling the shunt 16, thereby changing the treatment capacity of ultraviolet sterilization.
Example 3 the sterilization machine of example 1 was used for milk sterilization
To ensure adequate mixing of the milk as it moves through the PFA tube 4, the reynolds number (Re) and dean number (De) were calculated according to equations (1) and (2):
wherein rho is the density of the milk and is 1021.46kg/m2(ii) a Mu is the dynamic viscosity of cow milk and is 1.941 multiplied by 103Ns/m2(ii) a v is the flow rate of milk in the tube; d is the inner diameter of the PFA tube 4; dc is the PFA tube 4 surrounding the inner diameter.
Re < 2100 denotes a laminar flow state, Re > 4000 denotes a turbulent flow state, and Re is between them, which denotes a mixed flow state. De is the characterization of the flowing mode of the fluid in the coil, when the D/Dc is more than 0.03 and less than 0.1, the fluid in the coil generates secondary flow pits, and the mixing degree of the fluid can be enhanced.
An ultraviolet sterilization machine is arranged according to the combination of PFA pipes with different specifications and quartz sleeves with different outer diameters in the table 1, so that the milk is sterilized in two areas, Re and D/Dc are calculated, and the ultraviolet dose received by the milk is calculated according to the following formulas (5) and (6):
UV-C dose (mJ/cm)2) UV-C intensity (mW/cm)2) X treatment time(s). times.PFA tube 4UV-C transmittance (%) (6)
As can be seen from table 1: since the outer diameter of a section of the ultraviolet lamp tube is 19mm, the possible inner diameter of the quartz sleeve is at least 20 mm. It can be seen that the primary factor determining the ratio is the PFA tube specification. Therefore, when the outer diameter of the quartz sleeve is 20-30mm, PFA pipes with the diameters of 1 × 2mm, 1.5 × 2.5mm, 1.5 × 3mm, 2 × 3mm and 2 × 4mm should be selected; when the outer diameter of the quartz sleeve is 20-30mm, PFA tubes of 1 × 2mm, 1.5 × 2.5mm, 1.5 × 3mm, 2 × 3mm and 2 × 4mm should be used.
TABLE 1D/Dc values for PFA tubes of different specifications combined with quartz sleeves of different outer diameters
The performance of the sterilized milk was tested and the results are shown in table 2. It can be seen from table 2 that although the D/Dc values of 2 x 4mm pfa tubes met the requirements, the total number of bacteria did not meet the pasteurisation criteria. Probably because the ultraviolet transmittance is low due to the over-thick tube wall, the sterilization effect is further influenced. Therefore, the PFA tube specification of 1mm 2mm, 1.5mm 2.5mm, 2mm 3mm can be selected.
TABLE 2 Sterilization Effect under different PFA pipe specifications
Note: "-" indicates that less than 1 colony on the plate was not detected.
Comparative example 1 sterilizing effect of different ultraviolet sterilizing apparatuses
Adopts commercial direct-flow type and static ultraviolet sterilization equipment to sterilize milk, and the direct-flow type equipment (Ster)
New York, NY, USA) mainly consists of an ultraviolet lamp tube, a quartz sleeve wrapped outside the lamp tube, and a metal sleeve spaced from the quartz sleeve by 1.5 mm. During sterilization, milk flows between the quartz sleeve and the metal sleeve along the axial direction. Static type equipment (see the literature: MalekAmiliali et al, Inactivations of Staphylococcus aureus (ATCC 6538), Escherichia coli (ATCC 25922) and Pseudomonas aeruginosa (ATCC 9027) in Skimmed Bovine Milk UltraViolet-C Irradation, International Journal of Advanced Research (2015), Volume 3, Issue 5,387 395) consists of a metal box, the top of which is provided with an UltraViolet lamp tube. The sample is placed at the bottom of the box body and evenly spread in the circular sample cell, and the height of the sample is 1.5 mm.
Controlling the flow rate of milk in the direct-flow type equipment and the irradiation time of an ultraviolet lamp in the static type equipment, and controlling the surface ultraviolet dose of the milk in contact with the ultraviolet light in three ultraviolet sterilization modes to be 31mJ/cm2And determining the total number of bacteria.
The test results of the pasteurized milk obtained in example 3 and comparative example 1 are shown in table 3. As can be seen from Table 3, the total number of bacteria in cow's milk was the least and the intensity of bacteria was the highest after the cow's milk was sterilized by the spiral tube type apparatus (example 1) under the same UV dose. Therefore, the spiral tube type ultraviolet sterilizer has high sterilization intensity and high efficiency.
Table 3 test results of the pasteurized milk obtained in example 3 and comparative example 1
Example 4 changing cow milk flow (Q) to change UV dose
The PFA tube with an inner diameter of 1.5mm and an outer diameter of 2.5mm is selected.
Taking fresh milk, keeping milk temperature at 25 deg.C, passing through 5 sterilization zones, respectively controlling milk flow in tube at 50, 100, 200mL/min, respectively corresponding to ultraviolet dose of 65mJ/cm2、33mJ/cm2、16mJ/cm2(ii) a The cow milk is sterilized by ultraviolet and then is connected in a sterile bottle, and then is immediately put into crushed ice.
Meanwhile, fresh milk (the total number of colonies is 5.48 +/-0.03 log (CFU/mL) and the number of coliform groups is 2.77 +/-0.01 log (CFU/mL)) of the same batch is used for pasteurization (at 72 ℃ for 15s) as a control, and the pasteurized (at 72 ℃ for 15s) milk has the total number of colonies of 2.45 +/-0.05 log (CFU/mL) and does not contain the coliform groups.
The total bacterial count and coliform group of the cow milk before and after sterilization were determined, and the test results are shown in table 4:
the limit standard of China for the microorganisms of raw milk is 2 multiplied by 106(CFU/mL); the colony count limit for pasteurized milk was 50000(CFU/mL) and the coliform limit was 5 (CFU/mL). The data in table 4 show that raw milk, pasteurized milk and three doses of uv-pasteurized milk meet the requirements of the national standards (GB 19645-2010, GB 19301-2010). Wherein the milk flow is 100mL/min (ultraviolet dose is 33 mJ/cm)2) When the sterilizing effect is best, the flow is increased, and the ultraviolet irradiation time of the cow milk in the tube is shortened, so that the sterilizing effect is weakened; the flow rate is reduced, the flowing speed of the milk in the tube is reduced, the ultraviolet irradiation time is prolonged, but the flow rate is too low, the Reynolds number is too small, the milk is not mixed in the tube to a greater extent than when the flow rate is large, and the sterilization effect is weak.
Table 4 test results of example 4
Note: "-" indicates that less than 1 colony on the plate was not detected.
Example 5 varying the UV dose by varying the PFA tube 4 length
Selecting a PFA pipe 4 with the inner diameter of 1.5mm and the outer diameter of 2.5mm, controlling the flow rate of milk in the pipe to be 150mL/min, and enabling the milk to respectively pass through 2, 3, 4, 5 and 6 sterilization areas (the length of each sterilization area is 1m and the winding is 12 circles) through the opening and closing of a three-way valve 3, wherein the ultraviolet doses of 5 treatment modes are respectively 16, 23, 31, 39 and 47mJ/cm2. The cow milk is sterilized by ultraviolet and then is connected in a sterile bottle, and then is immediately put into crushed ice.
Meanwhile, fresh cow milk (the total number of colonies is 5.02 plus or minus 0.02log (CFU/mL) and the number of coliform groups is 2.02 plus or minus 0.02log (CFU/mL)) of the same batch is used for pasteurization (at 72 ℃ for 15s) as a control, and the pasteurized cow milk (at 72 ℃ for 15s) has the total number of colonies of 1.18 plus or minus 0.00log (CFU/mL) and does not contain the coliform groups.
The total bacterial count and coliform group of the cow milk before and after sterilization were determined, and the test results are shown in table 5:
as can be seen from the data in Table 5 combined with the national standards (GB 19645-2010 and GB 19301-2010), the total number of the ultraviolet sterilizing cow milk bacterial colonies and the number of the coliform bacteria with 5 parameters reach the requirements of the national standards. The PFA pipe 4 is wound for more than 3m, and the ultraviolet sterilization effect of the milk is equal to pasteurization (15 s at 72 ℃).
Table 5 test results of example 5
Note: "-" indicates that less than 1 colony on the plate was not detected.
Example 6 Effect of UV Sterilization on milk active proteins
The milk flow is 100mL/min and passes through 4 sterilization areas (the ultraviolet dose is 26 mJ/cm)2Recorded as UV4-100), and milk flow rate of 150mL/min, passing through 6 sterilization zones (ultraviolet dose of 47 mJ/cm)2Recorded as UV6-150), two sterilization parameters are taken as examples, milk immune globulin before and after ultraviolet sterilization is measuredThe contents of albumin (IgG, IgA, IgM) and lactoferrin, the activities of lactoperoxidase LPO and xanthine oxidase XO, and the control of raw milk (noted R) and pasteurized milk (72 ℃ for 15s) (noted H).
The test results are shown in table 6 and table 7 and fig. 5 and fig. 6: as can be seen from Table 6, the milk sterilized with two UV doses both met the requirements of the national standard for pasteurized milk. After ultraviolet sterilization, the number of spores shows that pasteurization can only kill the bacterial trophosome in the cow milk but can not kill the spores in the cow milk, and ultraviolet sterilization can kill the bacterial trophosome and part of the spores. As can be seen from table 7, fig. 5 and fig. 6, pasteurization resulted in a significant reduction in 4 immunologically active proteins, LPO and XO in cow milk, while two kinds of uv sterilization had no significant effect on these 6 bioactive substances, and thus high-activity cow milk could be produced by the uv sterilization method of the present invention.
Table 6 results of the sterilization test of example 6
Note: "-" indicates that less than 1 colony on the plate was not detected.
Table 7 results of activity test of example 6
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. An ultraviolet sterilization machine for producing high-activity liquid milk is characterized by comprising an ultraviolet sterilization component 15, wherein the ultraviolet sterilization component 15 comprises a gasket 1, an ultraviolet intensity monitor 2, a three-way valve 3, a PFA pipe 4, an ultraviolet lamp tube 5, a quartz sleeve 6 and a PFA pipe fixing clamp 7, the surface of the ultraviolet lamp tube 5 is covered with the quartz sleeve 6, the PFA pipe 4 is tightly wound around the quartz sleeve 6 and is fixed by the PFA pipe fixing clamp 7, no gap exists between the PFA pipe 4 and the quartz sleeve 6, each time the PFA pipe 4 is wound for 10-30 circles to serve as a sterilization area, the PFA pipes 4 in adjacent sterilization areas are connected through the three-way valve 3; a gasket 1 is arranged between the ultraviolet lamp tube 5 and the quartz sleeve 6; the ultraviolet intensity detector 2 is closely attached to the outside of the quartz sleeve 6 where the PFA tube is not wound.
2. The uv sterilizer of claim 1, wherein a feed pump 8 is provided at one side of the uv sterilizer, the PFA tube 4 is passed through the feed pump 8 at one end, and the liquid milk is fed into the pipe line through the feed pump 8.
3. The uv sterilizer of claim 1 or 2, further comprising a lamp holder 10 and a uv lamp holder 11, wherein the lamp holder 10 and the uv lamp holder 11 are used for fixing the uv lamp tube 5.
4. The ultraviolet sterilizer of any one of claims 1 to 3, further comprising a housing support 12, a stainless steel housing 13; the stainless steel housing 13 is supported by the housing bracket 12; a plurality of ultraviolet light tubes 5 are contained within a stainless steel housing 13.
5. The UV sterilizer of any one of claims 1 to 4, wherein the number of the UV sterilizing members 15 in the UV sterilizer is 1 to 100, and correspondingly, the number of the heating pipes 17 and the diverter 16 is 1 to 10; when the number of the ultraviolet sterilization components is multiple, the ultraviolet sterilization components are placed in parallel, and the treatment capacity of the ultraviolet sterilization machine can be 3-1200L/h.
6. A method for producing high-activity liquid milk by using the ultraviolet sterilization machine as claimed in any one of claims 1 to 5.
7. The method as claimed in claim 6, wherein the PFA tube 4 of the UV sterilizer is used in a specification of 1-2mm in inner diameter and 2-3mm in outer diameter.
8. The method according to claim 6 or 7, wherein the ratio of the surrounding inner diameter Dc of the PFA tube 4 to the inner diameter D of the PFA tube 4 in the ultraviolet sterilization device is between 0.03 and 0.1.
9. Method according to any of claims 6-8, characterized in that the liquid milk is heated to a certain temperature by means of a heating pipe before it is subjected to UV irradiation; during ultraviolet sterilization, the liquid milk can be kept at a certain temperature by a temperature control system, and the adjustable temperature range is 0-80 ℃.
10. Highly active liquid milk produced by the method of any one of claims 6 to 9.
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| CN2143499Y (en) * | 1992-11-03 | 1993-10-13 | 陈政统 | Ultra-violet sterilizer |
| CN200949062Y (en) * | 2006-09-19 | 2007-09-19 | 石有信 | Microwave ultraviolet disinfection decontaminating apparatus |
| CN204273101U (en) * | 2014-10-14 | 2015-04-22 | 荣成炭谷有限公司 | A kind of equipment for sterilization of milk sterilization |
| CN206108974U (en) * | 2016-08-25 | 2017-04-19 | 厦门水务水处理科技有限公司 | High -efficient STREAMING ultraviolet disinfection equipment of crossing |
| CN208883539U (en) * | 2018-09-30 | 2019-05-21 | 四川金澜科技有限公司 | A kind of ultraviolet sterilizer |
| CN209322516U (en) * | 2018-09-21 | 2019-08-30 | 青岛海尔施特劳斯水设备有限公司 | A kind of circulating water sterilizing unit |
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2020
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2143499Y (en) * | 1992-11-03 | 1993-10-13 | 陈政统 | Ultra-violet sterilizer |
| CN200949062Y (en) * | 2006-09-19 | 2007-09-19 | 石有信 | Microwave ultraviolet disinfection decontaminating apparatus |
| CN204273101U (en) * | 2014-10-14 | 2015-04-22 | 荣成炭谷有限公司 | A kind of equipment for sterilization of milk sterilization |
| CN206108974U (en) * | 2016-08-25 | 2017-04-19 | 厦门水务水处理科技有限公司 | High -efficient STREAMING ultraviolet disinfection equipment of crossing |
| CN209322516U (en) * | 2018-09-21 | 2019-08-30 | 青岛海尔施特劳斯水设备有限公司 | A kind of circulating water sterilizing unit |
| CN208883539U (en) * | 2018-09-30 | 2019-05-21 | 四川金澜科技有限公司 | A kind of ultraviolet sterilizer |
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