CN113016874A - Low-temperature high-quality milk sterilization method based on alternating magnetic field - Google Patents
Low-temperature high-quality milk sterilization method based on alternating magnetic field Download PDFInfo
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Abstract
The invention discloses a low-temperature high-quality milk sterilization method based on an alternating magnetic field, and belongs to the technical field of food preservation and storage. The method adopts a low-temperature high-quality milk sterilization device based on an alternating magnetic field to realize sterilization treatment on milk at the temperature of not higher than 65 ℃, considers the diamagnetic property of a milk liquid medium and the magnetic conductivity range of 50-90kHz, determines the material composition of a magnetic core in the low-temperature high-quality milk sterilization device, controls the excitation voltage value, the frequency and the waveform, and the treatment flow rate, and realizes the purpose of effectively sterilizing on the premise of keeping beneficial active substances in the milk as much as possible by reducing the sterilization temperature by at least 10 ℃. The method effectively prolongs the shelf life of the low-temperature milk, simultaneously reserves more beneficial active substances (lactoferrin, immunoglobulin, lactoperoxidase and the like) in the milk, and has the advantages of greenness, no pollution and more suitability for industrial production.
Description
Technical Field
The invention relates to a low-temperature high-quality milk sterilization method based on an alternating magnetic field, and belongs to the technical field of food preservation and storage.
Background
Milk is known as 'white blood', is rich in protein, fat, mineral substances, vitamins and various immunocompetence factors, and has the status and the function that food cannot replace in the dietary structure of people. In particular, its nutritional composition is close to that of human milk, so it is a major food for many infants instead of breast milk. The milk is rich in various bioactive components, various amino acids required by human body, and the like. And because the amino acid composition of the milk protein is quite close to the requirement of human body, the milk protein is praised as 'ideal protein'. But at the same time, milk is very easy to deteriorate due to the rich nutrient components of various microorganisms, so that an effective sterilization mode is required to prolong the preservation time.
Most of the current sterilization modes are thermal sterilization, such as pasteurization and ultrahigh pressure instant sterilization. The ultrahigh pressure instant sterilization has the advantages of long shelf life, thorough sterilization, convenient transportation and the like, but has great nutrition destructiveness on milk. Although the pasteurized milk has high nutrient preservation rate, the shelf life is short, and the transportation is limited by a cold chain.
Under the trend of consumer upgrading, consumers also pay more and more attention to food freshness and quality, so that the concept of fresh milk roots in the heart of the consumers. With the rise of equal logistics systems of fresh electric suppliers and the growth of normal-temperature milk business, a plurality of milk industries begin to occupy the pasteurized milk market. The sudden epidemic situation promotes the arousal of the health consciousness of the whole people and further stimulates the potential of fresh milk consumption. Data display of market research analysis and investment strategy discussion report of China fresh milk industry in 2020 + 2026 years: 2015-2019, the sales of fresh milk are increased by 6.13%, 8.22%, 9.71%, 10.67% and 11.56% proportionally, and the fresh milk is continuously increased for 5 years and enters a double-digit increase stage. Fresh milk is expected to be the main force for pulling the overall market growth of liquid milk, and will also be one of the key supporters for profitability of dairy enterprises. In addition, data provided by the X cat mall showed a comparable 150% increase in low milk sales in 2020.
The low shelf life of fresh milk is always a great problem puzzling the dairy industry, and how to improve the shelf life of fresh milk on the premise of keeping more nutrient substances is a major subject which needs to be overcome by researchers. Although emerging cold sterilization technologies such as high-voltage pulse electric field, ultrasonic wave, ultrahigh static pressure and the like may have certain advantages in maintaining the quality and the nutritional ingredients of food, the application is expanded due to the fact that the defects brought by the techniques are more limited. For example, the high-voltage pulse electric field is processed by a contact electric field, the metal polar plate of the high-voltage pulse electric field can generate various unknown electrochemical reactions and electrode pollution to milk, and the edible safety is unknown; the quality of the cow milk cannot be influenced macroscopically by ultrasonic waves, but the treatment amount is small, the treatment time is long, and the pollution and sterilization of metal probe residues are incomplete; the ultrahigh pressure equipment is expensive, the operation is complicated, only intermittent small-batch treatment can be carried out, and the denaturation of milk protein is serious.
In addition, the existing liquid food sterilization technology taking steam as a heat source faces huge challenges, the traditional milk processing plant heat sterilization technology heats continuous-flow milk products in a pipeline by steam, the continuous-flow milk products belong to intermittent heat treatment, the total amount of sewage, cooling water and cleaning water caused in the production process of the milk products accounts for about 3 times of the milk processing amount, and the milk products also have the problem of environmental pollution caused by supporting facilities such as a boiler room and the like. Therefore, there is a need to develop a new efficient non-contact electric field sterilization technology for sterilizing dairy products such as clean, green, low-temperature, and long-shelf-life milk, so as to solve the above problems.
Disclosure of Invention
In order to solve the problem of short shelf life of low-temperature milk on the premise of greatly retaining beneficial active substances in the milk, the invention provides the alternating magnetic field-based low-temperature high-quality milk sterilization method, so that the shelf life of the low-temperature milk is effectively prolonged, meanwhile, more beneficial active substances (lactoferrin, immunoglobulin, lactoperoxidase and the like) in the milk are retained, and compared with other emerging cold sterilization technologies such as high-voltage pulse electric field, ultrasonic waves, ultrahigh static pressure and the like, the method has the characteristics of being green and pollution-free and being more suitable for industrial production.
A low-temperature high-quality cow milk sterilization method based on an alternating magnetic field adopts a low-temperature high-quality cow milk sterilization device based on an alternating magnetic field to realize sterilization treatment on cow milk at the temperature of not higher than 65 ℃; the low-temperature high-quality cow milk sterilization device based on the alternating magnetic field comprises a sample inlet bottle, a sample receiving bottle, a peristaltic pump and low-temperature high-quality cow milk sterilization equipment;
the low-temperature high-quality cow milk sterilization equipment comprises: the device comprises a magnetic core, an excitation coil, a magnetic coupling pipe, a storage chamber, a processing chamber and an excitation power supply; wherein the magnetic core is an iron-nickel magnetic powder core iron core containing 50 wt% of iron and 50 wt% of nickel;
in the process of sterilizing the milk, the excitation voltage U applied to the excitation coil by the excitation power supply is 1000-1500V, and the waveform is as follows: bimodal pulse with frequency f of 50-90 kHz; the cow milk is driven by the peristaltic pump to flow through the processing chamber at a flow rate not exceeding 0.5L/min to complete the sterilization treatment.
Optionally, the length of the treatment chamber in the low-temperature high-quality milk sterilization device is 10-20cm, and the passing time of the milk in the treatment chamber is not more than 1min so as to ensure that the milk is always at a temperature not higher than 65 ℃.
Optionally, in the low-temperature high-quality cow milk sterilization equipment, the excitation coil is wound on the upper side of the magnetic core and is connected with an excitation power supply; the magnetic coupling pipes are wound on the left side and the right side of the magnetic core;
the storage chamber comprises a feeding storage chamber and a discharging storage chamber which are respectively arranged at the front and the rear of the magnetic core; the feeding storage chamber and the discharging storage chamber are communicated through the processing chamber, the processing chamber is positioned in the central part of the magnetic core and transversely penetrates through the central gap of the magnetic core, two ends of the processing chamber are respectively communicated with the magnetic coupling pipes wound on the left side and the right side of the magnetic core through a three-way connector, the magnetic coupling pipes are internally filled with food-grade agar solution with the concentration range of 2% -10% of sodium chloride to serve as a salt bridge, and the concentration range of agar in the agar solution is 0.5% -2.5%.
Optionally, in the low-temperature high-quality cow milk sterilization device, the ratio of the cross-sectional areas of the treatment chamber and the magnetic coupling pipe is 1:60-1: 1.
Optionally, the magnetic induction current density in the processing chamber is 1.5-2.8A/cm2The magnetic induction electric field intensity is 150-300V/cm.
Optionally, in the low-temperature high-quality milk sterilization device, the number of turns of the excitation coil above the magnetic core is 1-3, and the sum of the number of turns of the magnetic coupling tubes on two sides of the magnetic core is 25-45.
Optionally, in the low-temperature high-quality milk sterilization equipment, the effective magnetic path length l of the magnetic core is 20-100cm, and the cross-sectional area A is 8-25cm2。
Optionally, in the low-temperature high-quality cow milk sterilization equipment, the treatment chamber and the magnetic coupling tube have electrical insulation and are made of polytetrafluoroethylene, teflon, quartz, crystal, glass or enamel materials.
Optionally, in the low-temperature high-quality cow milk sterilization equipment, the sample inlet bottle is connected with the feed storage chamber, and the sample receiving bottle is connected with the discharge storage chamber.
The invention has the beneficial effects that: compared with the traditional pasteurization (the common sterilization temperature is 75 ℃ and 80 ℃), the method can effectively kill the microorganisms in the milk at a lower temperature (not more than 65 ℃), greatly prolongs the shelf life of the milk, and can effectively solve the key problems that the pasteurized milk has a short shelf life and the transportation is limited by a cold chain. Meanwhile, compared with the traditional pasteurization, the method has the advantages that the sterilization temperature is reduced by at least 10 ℃, so that the beneficial active substances (lactoferrin, immunoglobulin and lactoperoxidase) in the milk can be better reserved, the requirement of consumers on high-quality milk is met, and compared with other emerging cold sterilization technologies such as high-voltage pulse electric field, ultrasonic wave, ultrahigh static pressure and the like, the method is green and pollution-free and is more suitable for industrial production.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a front view of a low-temperature high-quality milk sterilization device based on an alternating magnetic field according to an embodiment of the present invention;
FIG. 2 is a schematic view of the overall structure of a low-temperature high-quality milk sterilizer based on an alternating magnetic field according to an embodiment of the present invention;
FIG. 3 is a side view of the low-temperature high-quality milk sterilization equipment based on an alternating magnetic field according to one embodiment of the present invention;
FIG. 4 is a top view of the low-temperature high-quality milk sterilization apparatus based on an alternating magnetic field according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of the size of the magnetic core of the low-temperature high-quality milk sterilization apparatus based on an alternating magnetic field according to an embodiment of the present invention.
FIG. 6 is a schematic diagram of an alternative magnetic field-based low-temperature high-quality milk sterilizer according to an embodiment of the present invention;
wherein, the sampling bottle 101, the peristaltic pump 102, the excitation power supply 103, the sample receiving bottle 104; the aging treatment apparatus includes: the device comprises an O-shaped magnetic core 201, an excitation coil 202, a magnetic coupling pipe 203, a material storage chamber 204, a processing chamber 205, a liquid outlet pipe 206, a three-way connector 207 and a base 208; the aging treatment device comprises two storage chambers 204, wherein one storage chamber 204 is connected with a liquid inflow port 209, and the other storage chamber 204 is connected with a liquid outflow port 210;
in fig. 1-4, the arrows indicate the material flow direction.
Detailed Description
The first embodiment is as follows:
the present embodiment provides a low-temperature high-quality milk sterilization apparatus based on an alternating magnetic field, please refer to fig. 1, the low-temperature high-quality milk sterilization apparatus includes: a magnetic core 201, an excitation coil 202, a magnetic coupling pipe 203, a material storage chamber 204, a processing chamber 205 and an excitation power supply; wherein the magnetic core is made of iron-nickel magnetic powder core iron core containing 50 wt% of iron and 50 wt% of nickel.
The excitation coil 202 is wound on the upper side of the magnetic core 201 and is connected with an excitation power supply; the magnetic coupling pipe 203 is wound on the left side and the right side of the magnetic core 201;
the storage chamber 204 comprises a feeding storage chamber and a discharging storage chamber which are respectively arranged at the front and the rear of the magnetic core 201; the feeding storage chamber and the discharging storage chamber are communicated through a processing chamber 205, the processing chamber is positioned in the center of the magnetic core and transversely penetrates through the central gap of the magnetic core, two ends of the processing chamber 205 are respectively communicated with magnetic coupling pipes 203 wound on the left side and the right side of the magnetic core 201 through a three-way connector 207, the magnetic coupling pipes are filled with food-grade agar solution with the sodium chloride concentration range of 2% -10% to serve as salt bridges, and the agar concentration range in the agar solution is 0.5% -2.5%;
in the process of sterilizing the milk, the excitation voltage U applied to the excitation coil 202 by the excitation power supply is 1000-1500V, and the waveform is as follows: bimodal pulse with frequency f of 50-90 kHz; the milk flows into the treatment chamber from the feeding storage chamber at a flow speed of not more than 0.5L/min, the length of the treatment chamber is 10-20cm, the milk flows into the discharging storage chamber after being treated by the alternating magnetic field in the treatment chamber to finish sterilization treatment, and in the treatment process, the passing time of the milk in the treatment chamber is not more than 1min so as to ensure that the milk is always at the temperature of not more than 65 ℃.
The application considers that different magnetic cores have difference in eddy current effect induced in a secondary circuit composed of conductive liquid during excitation due to different initial magnetic permeability, saturation magnetic induction intensity and loss. According to the previous research, based on the diamagnetic characteristics of the milk liquid medium and the magnetic permeability range (relative magnetic permeability 1.0013-1.0015) of 50-90kHz, the magnetic core selected is an iron-nickel magnetic powder core iron core, wherein the iron-nickel magnetic powder core comprises 50 wt% of iron and 50 wt% of nickel, the effective sterilization treatment on the milk can be completed under the conditions that the excitation voltage is 1000-1500V, the double-peak pulse waveform and the frequency is 50-90kHz, and simultaneously the nutrient substances are retained to the maximum extent, and the characteristic parameters of the magnetic core are shown in the following table 1:
table 1: characteristic parameters of magnetic core
Example two:
the present embodiment provides an alternating magnetic field-based low-temperature high-quality milk sterilization treatment device, referring to fig. 2, the device includes: a sample feeding bottle 101, a peristaltic pump 102, an excitation power supply 103, a sample receiving bottle 104 and the low-temperature milk sterilization device 200 in the first embodiment.
In this embodiment, the magnetic core 201 in the low-temperature milk sterilization processing apparatus 200 is an O-shaped magnetic core.
As shown in fig. 2 to 4, the low-temperature milk sterilization processing apparatus 200 includes: the device comprises an O-shaped magnetic core 201, an excitation coil 202, a magnetic coupling pipe 203, a material storage chamber 204, a processing chamber 205, a liquid outlet pipe 206, a three-way connector 207 and a base 208.
As shown in fig. 2, in the low-temperature milk sterilization apparatus 200, the excitation coil 202 is wound on the upper side of the O-shaped magnetic core 201, and the magnetic coupling pipes 203 are wound on the left and right sides of the O-shaped magnetic core 201. The excitation coil 202 is connected to the excitation power supply 103.
As can be seen from the side view shown in FIG. 3 and the top view shown in FIG. 4, the low-temperature milk sterilization treatment apparatus 200 comprises two storage chambers 204 respectively disposed at the front and rear positions of the O-shaped magnetic core 201, and the two storage chambers 204 are communicated through a treatment chamber 205; one of the reservoirs 204 (for convenience of description, the reservoir 204 is referred to as a feed reservoir) is connected to the fluid inlet 209, and the other reservoir 204 (for convenience of description, the reservoir 204 is referred to as a discharge reservoir) is connected to the fluid outlet 210. Wherein the fluid inlet 209 is an inlet to the processing chamber 205 and the fluid outlet 210 is an outlet from the processing chamber 205. As shown in fig. 3, the processing chamber 205 between the liquid inflow port 209 and the liquid outflow port 210 is connected to the agar-filled magnetic coupling pipe 203.
The two storage chambers 204 are communicated through the processing chamber 205, the sample inlet 301 is arranged below the storage chamber 204 at the front side of the O-shaped magnetic core 201, milk enters the feeding storage chamber 204 from the sample inlet, and then flows into the processing chamber 205 through the liquid inflow port 209 on the processing chamber 205, after the processing chamber 205 is processed by a magnetic induction electric field, the milk enters the discharging storage chamber 204 through the liquid outflow port 210 on the processing chamber 205, after the two storage chambers 204 are filled with milk, the processed milk flows out of the discharging storage chamber 204, and then flows into the sample receiving bottle 104 from the sample outlet 302.
As can be seen, the magnetic coupling 203, the reservoir 204 and the process chamber 205 are connected by a three-way joint 207.
The low-temperature high-quality cow milk sterilization device based on the alternating magnetic field provided by the embodiment can be used for continuously treating cow milk, and the sample introduction bottle 101 and the sample receiving bottle 104 in fig. 2 are respectively used for storing cow milk before and after treatment.
In the treatment process, the excitation power supply 103 applies an excitation voltage of 1000-1500V, a waveform of double-peak pulse and a frequency f of 50-90kHz to the excitation coil 202 so as to enable the magnetic core 201 wound by the excitation coil 202 to generate an alternating magnetic field, the alternating magnetic field can generate an alternating induction electric field in the magnetic coupling pipe 203 filled with agar, and the cow milk has certain electric conductivity (0.1-10S/m) and magnetic permeability (relative magnetic permeability 1.0013-1.0015), so that the cow milk can be sterilized under the synergistic action of the magnetic induction heat effect (eddy current) and the non-heat effect (induction electric field) of the alternating magnetic field.
In the low-temperature high-quality milk sterilization equipment 200, the sum of the turns of the excitation coil above the O-shaped magnetic core 201 is 1-3 turns, and the sum of the turns of the magnetic coupling pipes on the two sides of the magnetic core 201 is 25-45 turns. The ratio of the cross-sectional areas of the process chamber 205 and the magnetic coupling 203 ranges from 1:60 to 1: 1. The length of the processing chamber 205 is 10-20cm, and the magnetic induction current density in the processing chamber is 1.5-2.8A/cm2The magnetic induction electric field intensity is 150-300V/cm.
Considering the diamagnetic characteristics of milk liquid medium and the magnetic permeability range of 50-90kHz (relative magnetic permeability 1.0013-1.0015)) In the low-temperature high-quality milk sterilization apparatus 200, an iron-nickel magnetic powder core iron core containing 50 wt% of iron and 50 wt% of nickel is used as the O-shaped magnetic core 201, and the characteristic parameters of the magnetic core are as shown in table 1 above. The effective magnetic path length l of the magnetic core 201 is 20-100cm, and the cross-sectional area A of the magnetic core 201 is 8-25cm2The magnetic flux of the magnetic core 201 is 0.00027-0.002Wb, the initial magnetic permeability u of the magnetic core is 1690-1800(H/m), and the magnetic flux density B is 0.3-1.4T. As shown in fig. 5, the effective magnetic path length l is (d1+ d2) × 2.
When the low-temperature high-quality milk sterilization equipment 200 is used for sterilization treatment, the treatment speed is not more than 0.5L/min.
In the treatment process, in order to maintain the sterilization temperature at not higher than 65 ℃ all the time, a constant temperature jacket is arranged on the outer layer of the treatment chamber 205.
The process chamber 205 and the magnetic coupling 203 are electrically insulating and may be made of teflon, quartz, crystal, glass, or enamel.
The application provides a low temperature high quality cow milk sterilization processing apparatus based on alternating magnetic field can once only accomplish continuous type through process chamber 205 and handle.
In order to verify the sterilization effect of the alternating magnetic field-based low-temperature high-quality milk sterilization method, the following third embodiment and fourth embodiment are obtained by performing sterilization experiments on raw milk.
The experimental procedure was as follows:
(1) raw milk was purchased from local dairy plants and milk samples were taken from fresh milk of healthy cows as a white, homogeneous, sediment-free fluid.
(2) And (2) putting the raw milk purchased in the step (1) into an ice box, immediately transporting the raw milk back to a laboratory, subpackaging the samples into 500ml sterile bottles in a sterile ultra-clean workbench, and storing at 4 ℃.
(3) In order to ensure the rigor of the experiment, the pipeline is cleaned by 4% sodium hydroxide solution, 10% hypochlorous acid disinfectant and sterile water before each experiment.
The evaluation indexes and the experimental method are as follows:
the total number of microorganisms detection method comprises the following steps: the determination method refers to a plate counting method in GB 4789.2-2016 (national food safety Standard food microbiology test colony Total determination);
the detection method of the escherichia coli group comprises the following steps: the determination method refers to a flat plate counting method in GB 4789.3-2016 (national food safety Standard food microbiology test coliform group count);
the detection method of staphylococcus aureus groups comprises the following steps: the determination method is carried out according to qualitative inspection in GB 4789.10-2016 (national food safety Standard food microbiology inspection Staphylococcus aureus inspection);
the salmonella group detection method comprises the following steps: the determination method is carried out by referring to qualitative inspection in GB 4789.4-2016 (national food safety Standard for food microbiology inspection for Salmonella) inspection;
lactoferrin assay method: the determination method is carried out according to the method in T/TDTIA 006 2019 liquid chromatography for determining lactoferrin in milk and dairy products;
immunoglobulin assay methods: the determination method refers to the method in SN/T3132-2012 "enzyme-linked immunosorbent assay for determining bovine immunoglobulin G in exported cow milk product";
the lactoperoxidase determination method comprises the following steps: the determination method is carried out according to the method in CAC/GL 13-1991 milk guide rule for lactoperoxidase fresh-keeping raw materials;
EXAMPLE III
The present embodiment provides a low-temperature high-quality milk sterilization method based on an alternating magnetic field, and the low-temperature high-quality milk sterilization processing apparatus based on an alternating magnetic field described in the second embodiment is adopted.
Specifically, as shown in fig. 2, the adopted low-temperature milk sterilization device based on the magnetic induction electric field comprises: a sample feeding bottle 101, a peristaltic pump 102, an excitation power supply 103, a sample receiving bottle 104 and a sample aging treatment device 200. The aging treatment apparatus 200 includes: an O-shaped magnetic core 201, an excitation coil 202, a magnetic coupling pipe 203, a material storage chamber 204, a processing chamber 205, a liquid outlet pipe 206, a three-way connector 207 and a base 208.
In this embodiment, the exciting coil 202 is wound over the O-shaped magnetic core 201, the number of turns of the exciting coil 202 is 1, an exciting voltage of 1500V is applied to the exciting coil 202 by the exciting power supply 103, the O-shaped magnetic core 201 is an iron-nickel magnetic powder core, wherein the iron-nickel magnetic powder core comprises 50 wt% of iron and 50 wt% of nickel, and the characteristic parameters of the magnetic core are as shown in table 1 above.
The O-shaped magnetic core 201 has an initial permeability of 1700(H/m), a magnetic flux density of 0.6T during operation, and an effective magnetic conductive area of 12cm2. The magnetic coupling pipe 203 is wound on the left side and the right side of the magnetic core 201, and the total number of turns of the magnetic coupling pipe 203 is 25; magnetic coupling 203 is supported on agar containing 5% sodium chloride to act as a salt bridge; the storage chamber 204 and the processing chamber 205 are used as supports for milk, the storage chamber 204 and the processing chamber 205 are in a state of communication, and the cross-sectional area of the processing chamber 205 is 0.32cm2The cross-sectional area of the magnetic coupling pipe 203 is 0.64cm2(the ratio of the cross-sectional area of the processing chamber 205 to the cross-sectional area of the magnetic coupling 203 is about 1:2), cow milk is introduced from the sample bottle 101 into the storage chamber 204 via the peristaltic pump 103, and then enters the processing chamber 205.
When milk (25 ℃) with the conductivity of 5400S/m measured by a conductivity meter flows through the treatment chamber 205, the effective potential difference received by the treatment chamber 205 is 1872V measured by a general meter at both ends, the length of the treatment chamber 205 at both sides is 12cm, and the electric field intensity is 156V/cm. When the treatment chamber 205 was filled with cow's milk, the impedance was 3500 Ω/10cm as measured by the impedance analyzer, and thus the induced current in the treatment chamber 205 was 2.6A and the induced current density was 5.7A/cm2The milk inlet 301 is submerged in the vial 101, while the milk outlet 302 is located in the vial 104 for continuous flow processing. When the flow of the sample outlet is 20ml/min, the retention time of the milk in the processing chamber 205 is 15s, and the test of an infrared thermal imager shows that after the raw milk with the initial room temperature of 25 ℃ is normally circulated in the low-temperature high-quality milk sterilization equipment with the alternating magnetic field, the temperature of the milk in the processing chamber 205 is increased to 65 ℃.
The inspection shows that the total number of microorganisms in the treated milk is effectively controlled within 30CFU/ml, pathogenic bacteria such as escherichia coli, staphylococcus aureus and salmonella which are harmful to human bodies are not detected, and the national safety standard of food is met. The immunoglobulin content of fresh milk in the cow milk is 244mg/ml, which is reduced by 18%; the lactoferrin content is 53mg/L, which is reduced by 16%; the lactoperoxidase content was 1771mg/ml, which was only a 19% reduction. In the storage period experiment of milk, the shelf life of the low-temperature milk sterilized by the device can reach more than 50 days.
Example four
The specific implementation measure is different from the third example in that the excitation power supply 103 applies an excitation voltage of 1000V to the excitation coil 202. The effective potential difference experienced by the process chamber 205 was 1230V, measured by a general electric meter across the chamber 205, and the chamber 205 was 12cm in length and the electric field strength was 156V/cm. When the treatment chamber 205 was filled with cow's milk, the impedance thereof was 3800. omega./10 cm as measured by the impedance analyzer, and thus the induced current in the treatment chamber 205 was 1.6A and the induced current density was 3.2A/cm2The milk inlet 301 is submerged in the vial 101, while the milk outlet 302 is located in the vial 104 for continuous flow processing. When the flow of the sample outlet is 20ml/min, the retention time of the cow milk in the treatment chamber 205 is 15s, and the test of an infrared thermal imager shows that after the cow milk at the initial room temperature of 25 ℃ normally circulates in the low-temperature high-quality cow milk sterilization equipment with the alternating magnetic field, the temperature of the cow milk in the treatment chamber 205 rises to 46 ℃.
Through inspection, the total number of microorganisms in the treated milk is effectively controlled within 100CFU/ml, pathogenic bacteria such as escherichia coli, staphylococcus aureus and salmonella which are harmful to human bodies are not detected, and the national safety standard of food is met. The immunoglobulin content in cow milk is 292mg/ml, which is reduced by 11%; the lactoferrin content is 57mg/L, which is reduced by only 10%; the lactoperoxidase content was 1880mg/ml, which was only a 14% reduction. In the storage period experiment of milk, the shelf life of the low-temperature milk sterilized by an alternating magnetic field instrument can reach more than 30 days.
To further highlight the advantages of the present application over pasteurization, the present application provides the following comparative examples:
comparative example 1
The specific implementation measures are the same as those in the third example, and the difference is that treatment is not carried out by an alternating magnetic field device, and pasteurization is simulated: setting the temperature of the constant-temperature water bath kettle to be 77 ℃, aseptically sampling raw milk in a 5ml aseptic test tube, placing a sterilized temperature probe in the center of the liquid level, heating to 75 ℃, keeping for 15 seconds, taking out the sample, and placing the sample in a refrigerator at 4 ℃ for cooling.
The shelf life of the pasteurized milk at 75 ℃ and the retention of the contained beneficial active substances are evaluated according to the same method of the three examples, and the results show that the total number of microorganisms in the pasteurized milk at 75 ℃ is 3500CFU/ml, and neither coliform group, golden staphylococcus group nor salmonella group is detected, thereby meeting the national food safety standard. The fresh milk immunoglobulin content after being processed by the pasteurization at 75 ℃ is 185mg/ml, which is reduced by 38 percent; the lactoferrin content is 40mg/L, which is reduced by 36%; the lactoperoxidase content was 1421mg/ml, which was a 35% reduction, in the storage period test of milk, the shelf life of milk pasteurized at 75 ℃ was 21 days.
Comparative example No. two
The specific implementation measures are the same as those in the third example, and the difference is that treatment is not carried out by an alternating magnetic field device, and pasteurization is simulated: setting the temperature of the constant-temperature water bath kettle to 82 ℃, aseptically sampling raw milk in a 5ml aseptic test tube, placing the sterilized temperature probe in the center of the liquid level, heating to 80 ℃, keeping for 15 seconds, taking out the sample, and placing the sample in a refrigerator at 4 ℃ for cooling.
The shelf life of the pasteurized 80 ℃ milk and the retention of the contained beneficial active substances are evaluated according to the same method of the three examples, and the results show that the total number of the microorganisms in the pasteurized 80 ℃ processed fresh milk is 700CFU/ml, no coliform group, golden yellow staphylococcus group and salmonella group are detected, and the national food safety standard is met, the immunoglobulin content of the pasteurized 80 ℃ processed fresh milk is 166mg/ml, which is reduced by 43%; the lactoferrin content is 38mg/L, which is reduced by 40%; the lactoperoxidase content was 1290mg/ml, which was a 41% reduction, in the storage period test of milk, the shelf life of milk pasteurized at 80 ℃ was 30 days.
Comparing the third embodiment with the first embodiment, the total number of microorganisms in the fresh milk can be effectively controlled within 30CFU/ml after the device is processed at 65 ℃, pathogenic bacteria escherichia coli, staphylococcus aureus and salmonella which are harmful to human bodies are not detected, and the national safety standard of food is met. Moreover, the immunoglobulin content of the fresh milk is 244mg/ml, which is reduced by 18 percent; the lactoferrin content is 53mg/L, which is reduced by 16%; the lactoperoxidase content was 1771mg/ml, which was only a 19% reduction. In the storage period experiment of milk, the shelf life of the low-temperature milk sterilized by the device can reach more than 50 days.
In the traditional pasteurization, the total number of microorganisms in the fresh milk treated at 75 ℃ is still as high as 3500CFU/ml, and although no escherichia coli group, golden staphylococcus group or salmonella group is detected and meets the national safety standard of foods, the immunoglobulin content of the fresh milk treated at 75 ℃ by the pasteurization is 185mg/ml, which is reduced by 38%; the lactoferrin content is 40mg/L, which is reduced by 36%; the lactoperoxidase content was 1421mg/ml, which was a 35% reduction, in the storage period test of milk, the shelf life of milk pasteurized at 75 ℃ was 21 days.
Therefore, the device can sterilize the raw milk at a lower temperature, the sterilization effect is far higher than that of the traditional pasteurization, and in addition, because the device sterilizes the raw milk at a lower temperature, the substances beneficial to the human body, such as fresh milk immunoglobulin, lactoferrin, lactoperoxidase and the like, are also kept more.
Furthermore, through the fourth embodiment, it can be seen that, by adjusting corresponding parameters, the application can perform sterilization at a lower temperature (46 ℃), the total number of microorganisms is effectively controlled within 100CFU/ml, pathogenic bacteria escherichia coli, staphylococcus aureus and salmonella which are harmful to human bodies are not detected, and the national safety standards of food are met. The immunoglobulin content of the fresh milk processed by the instrument is 292mg/ml, which is reduced by 11 percent; the lactoferrin content is 57mg/L, which is reduced by only 10%; the lactoperoxidase content was 1880mg/ml, which was only a 14% reduction. In the storage period experiment of milk, the shelf life of the low-temperature milk sterilized by an alternating magnetic field instrument can reach more than 30 days.
Claims (9)
1. A low-temperature high-quality cow milk sterilization method based on an alternating magnetic field is characterized in that a low-temperature high-quality cow milk sterilization device based on an alternating magnetic field is adopted to sterilize cow milk at the temperature of not higher than 65 ℃; the low-temperature high-quality cow milk sterilization device based on the alternating magnetic field comprises a sample inlet bottle, a sample receiving bottle, a peristaltic pump and low-temperature high-quality cow milk sterilization equipment;
the low-temperature high-quality cow milk sterilization equipment comprises: the device comprises a magnetic core, an excitation coil, a magnetic coupling pipe, a storage chamber, a processing chamber and an excitation power supply; wherein the magnetic core is an iron-nickel magnetic powder core iron core containing 50 wt% of iron and 50 wt% of nickel;
in the process of sterilizing the milk, the excitation voltage U applied to the excitation coil by the excitation power supply is 1000-1500V, and the waveform is as follows: bimodal pulse with frequency f of 50-90 kHz; the cow milk is driven by the peristaltic pump to flow through the processing chamber at a flow rate not exceeding 0.5L/min to complete the sterilization treatment.
2. The alternating magnetic field-based low-temperature high-quality milk sterilization method according to claim 1, wherein the length of the treatment chamber in the low-temperature high-quality milk sterilization equipment is 10-20cm, and the milk passes through the treatment chamber for no more than 1min to ensure that the milk is always at a temperature not higher than 65 ℃.
3. The alternating magnetic field-based low-temperature high-quality milk sterilization method according to claim 2, wherein in the low-temperature high-quality milk sterilization device, the excitation coil is wound on the upper side of the magnetic core and is connected with an excitation power supply; the magnetic coupling pipes are wound on the left side and the right side of the magnetic core;
the storage chamber comprises a feeding storage chamber and a discharging storage chamber which are respectively arranged at the front and the rear of the magnetic core; the feeding storage chamber and the discharging storage chamber are communicated through the processing chamber, the processing chamber is positioned in the central part of the magnetic core and transversely penetrates through the central gap of the magnetic core, two ends of the processing chamber are respectively communicated with the magnetic coupling pipes wound on the left side and the right side of the magnetic core through a three-way connector, the magnetic coupling pipes are internally filled with food-grade agar solution with the concentration range of 2% -10% of sodium chloride to serve as a salt bridge, and the concentration range of agar in the agar solution is 0.5% -2.5%.
4. The alternating magnetic field-based low-temperature high-quality milk sterilization method according to claim 3, wherein in the low-temperature high-quality milk sterilization apparatus, the ratio of the cross-sectional areas of the treatment chamber and the magnetic coupling pipe is in the range of 1:60 to 1: 1.
5. The alternating magnetic field-based low-temperature high-quality milk sterilization method according to claim 4, wherein the magnetic induction current density in the treatment chamber is 1.5-2.8A/cm2The magnetic induction electric field intensity is 150-300V/cm.
6. The alternating magnetic field-based low-temperature high-quality milk sterilization method according to claim 5, wherein in the low-temperature high-quality milk sterilization device, the number of turns of the excitation coil above the magnetic core is 1-3, and the sum of the number of turns of the magnetic coupling tubes on both sides of the magnetic core is 25-45.
7. The alternating magnetic field-based low-temperature high-quality milk sterilization method according to claim 6, wherein the effective magnetic path length l of the magnetic core in the low-temperature high-quality milk sterilization equipment is 20-100cm, and the cross-sectional area A is 8-25cm2。
8. The alternating magnetic field-based low-temperature high-quality milk sterilization method according to claim 7, wherein in the low-temperature high-quality milk sterilization apparatus, the treatment chamber and the magnetic coupling tube have electrical insulation and are made of polytetrafluoroethylene, teflon, quartz, crystal, glass or enamel materials.
9. The alternating magnetic field-based low-temperature high-quality milk sterilization method according to claim 8, wherein in the low-temperature high-quality milk sterilization apparatus, the sample inlet bottle is connected with the feed storage chamber, and the sample receiving bottle is connected with the discharge storage chamber.
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