CN107279261B - Liquid cooling sterilizing and fresh keeping method for fresh egg - Google Patents

Abstract

The invention discloses a liquid cooling sterilization and preservation method for fresh eggs, and belongs to the field of egg product processing. The invention creatively converts high-density CO₂The sterilization technology is nested with a stirrer, and the egg liquid is treated by combining the ultrasonic and ultrahigh pressure sterilization technologies, so that the problem of CO generated is solved₂Poor diffusion and dissolution effects in egg liquid products; the killing capacity of the three technologies to salmonella is improved by 3-4 orders of magnitude (1000-10000 times) under the synergistic effect, and the egg liquid product is thoroughly sterilized. According to storage tests, the shelf life of the egg liquid product obtained by sterilization is remarkably prolonged, and can reach 95 days under refrigeration and 45 days at room temperature.

Description

Method of cold sterilization and preservation of fresh egg liquid

technical field

The invention relates to the technical field of egg processing, in particular to a method for cold sterilization and preservation of fresh egg liquid.

Background technique

Because the thermal denaturation and thermal coagulation temperature of protein in egg liquid is very low, especially the thermal denaturation temperature of most proteins in egg white is 62℃～68℃, even if high temperature or low temperature and long-term heat sterilization are used, it is easy to change the egg liquid. It is difficult to maintain the state of fresh egg liquid by forming a thermal gel. Therefore, the sterilization and extension of shelf life of egg liquid in fresh state is a worldwide problem.

At present, there are mainly two traditional methods for sterilization of egg liquid at home and abroad: pasteurization (low temperature sterilization method) and ultra-high temperature instantaneous heat sterilization. These two traditional methods have the following problems:

1) Pasteurization: The sterilization time is long and the protein is prone to coagulation and denaturation, which causes the egg liquid to form adhesion and coagulation in the sterilization pipeline during the production process, block the pipeline, and also affect the foaming, emulsification and other functional properties of the egg liquid. Do not use as egg wash in fresh state.

2) Ultra-high temperature instant heat sterilization: the sterilization time is short, and it is difficult to completely sterilize and kill a heat-resistant pathogen; increasing the heat sterilization time and temperature will cause the protein to coagulate and denature, which not only leads to a complete change in the properties of the egg liquid, Can not keep fresh egg liquid state.

At present, the application of non-thermal sterilization technology in egg sterilization mainly includes high-density carbon dioxide sterilization technology and ultra-high pressure sterilization technology. However, there are still some problems in the application of these non-thermal sterilization technologies to egg liquid:

1) High-density carbon dioxide technology has long sterilization time and poor sterilization effect; due to the high viscosity of egg liquid, it hinders the uniform diffusion of carbon dioxide molecules in the egg liquid and the contact with microorganisms.

2) Ultra-high pressure sterilization technology is difficult to completely kill the microorganisms in the egg liquid at 100 ~ 300pa, and it is easy to cause egg liquid denaturation above 300mpa.

In the prior art scheme, there is also a combination of high-density CO ₂ sterilization technology (DPCD) and ultra-high temperature pasteurization, and adding compound preservatives to preserve egg liquid under low temperature cold chain.

However, in this solution, the egg liquid is a viscous liquid, and the higher viscosity hinders the uniform diffusion of _CO molecules in the egg liquid and the contact with microorganisms, thereby weakening its sterilization effect. Due to the addition of compound preservatives , changed the composition and composition of the egg liquid, and also changed the foaming, gelling and emulsifying properties of the egg liquid when it was applied, and chemical preservatives were used. Ultra-high temperature pasteurization (70-74℃ for 120s) is a heat treatment process, which has a serious impact on the quality of egg liquid.

At present, high-density carbon dioxide sterilization technology has not been applied in combination with ultrasonic wave and ultra-high pressure in the sterilization and preservation of egg liquid at home and abroad.

SUMMARY OF THE INVENTION

Aiming at the defects of a single sterilization method and two synergistic sterilization methods in the prior art, the present invention provides a method for cold sterilization and preservation of fresh egg liquid, which adopts an improved high-density CO ₂ sterilization technology and combines Ultrasonic and ultra-high pressure sterilization technology treats the egg liquid, which solves the problem that the _CO2 produced by the above method has poor diffusion and dissolving effect in the egg liquid product; the synergistic effect enhances the sterilization effect and achieves the purpose of prolonging the shelf life of the egg liquid product .

In order to achieve the above object, a method for cold sterilization and preservation of fresh egg liquid provided by the present invention comprises the following steps:

1) Pretreatment of eggs:

Choose fresh eggs that meet hygienic standards, wash the surface of the egg shell with clean water and air dry, then beat the eggs in a clean environment, take the egg liquid and stir it evenly;

2) High-density CO ₂ sterilization treatment:

The uniform egg liquid is placed in high-density CO ₂ , the pressure is 4-10Mpa, the stirring speed is 50-150rp and the temperature is 20-30°C for sterilization treatment for 5-25min, and then the treated egg liquid is aseptically packaged/sterilized. Filling; obtaining the primary product; the method increases the diffusion and dissolution rate of _CO2 in the egg liquid;

3) Ultra-high pressure and ultrasonic co-processing:

The primary product is placed in an ultrasonic treatment container, the ultrasonic power is 50-220W/cm ² , and the treatment is carried out for 5-25min; 20min, take out after depressurization, it is the final product. The method enhances the penetration of _CO2 into microorganisms and destroys the cell structure, kills the microorganisms in the egg liquid product, and significantly prolongs the shelf life of the egg liquid while maintaining the quality of the egg liquid.

Still further, in the step 2), the sterilization treatment time is 5-15 min.

Still further, in the step 2), aseptic packaging/aseptic filling: turn on ultraviolet rays and ozone, and perform aseptic packaging and aseptic filling.

Still further, in the step 3), the power of the ultrasonic treatment is 120-180W/cm ² , and the time is 12-20 minutes;

Still further, in the step 3), the ultra-high pressure treatment pressure is 100-300 MPa, and the time is 8-15 min.

The beneficial effects of the present invention are:

(1) The present invention is aimed at the problems of high viscosity of egg liquid and difficulty in diffusing and dissolving CO ₂ , adding stirring treatment in the high-density CO ₂ sterilization process, and further utilizing ultrasonic wave or ultra-high pressure treatment to further enhance the transfer of CO ₂ to microbial cells At the same time, the shear pressure generated by ultrasonic waves and the high static pressure generated by turbulence or ultra-high pressure are used to destroy the microbial cell structure, thereby greatly improving the sterilization effect, and the killing ability of Salmonella is increased by 3 to 4 orders of magnitude (1000 ~10,000 times), to achieve complete sterilization of egg liquid products.

(2) The shelf life of the egg liquid product obtained by the sterilization of the present invention is significantly prolonged, and can reach 95 days under refrigeration and 45 days at room temperature.

Description of drawings

Fig. 1 is a graph showing the influence of stirring speed on sterilization effect in high-density carbon dioxide sterilization treatment;

Fig. 2 is a comparison diagram of the killing effect of different egg liquid sterilization methods on Salmonella;

In the figure, 1- initial contaminated egg liquid; 2- ordinary high-density carbon dioxide sterilization method; 3-Ultra-high temperature pasteurization method; 4- high-density carbon dioxide method; 5- high-density carbon dioxide synergistic ultrasonic method; High pressure method; 7-high-density carbon dioxide synergistic ultrasonic and ultra-high pressure method;

Figure 3 is a graph comparing the sterilization conditions of the four examples.

Detailed ways

In order to better explain the present invention, the main content of the present invention is further illustrated below in conjunction with specific embodiments, but the content of the present invention is not limited to the following embodiments.

A method for cold sterilization and preservation of fresh egg liquid, comprising the following steps:

1) Pretreatment of eggs:

Choose fresh eggs that meet hygienic standards, wash the surface of the egg shell with clean water and air dry, then beat the eggs in a clean environment, take the egg liquid and stir it evenly;

2) High-density CO ₂ sterilization treatment:

The uniform egg liquid is placed in high-density CO ₂ , the pressure is 4-10Mpa, the stirring speed is 50-150rp and the temperature is 20-30°C for sterilization treatment for 5-25min, and then the treated egg liquid is aseptically packaged/sterilized. Filling; obtaining the primary product; the method increases the diffusion and dissolution rate of _CO2 in the egg liquid;

3) Ultra-high pressure and ultrasonic co-processing:

The primary product is placed in an ultrasonic treatment container, the ultrasonic power is 50-220W/cm ² , and the treatment is carried out for 5-25min; 20min, take out after depressurization, it is the final product.

1. The influence of different stirring speeds on the sterilization effect

(1) Pretreatment of eggs: take fresh eggs that meet the hygienic standards as raw materials, wash the surface of the egg shell with clean water and air dry, then beat the eggs in a clean environment, take the egg liquid and stir evenly.

(2) In order to investigate the influence of different stirring speeds on the bactericidal effect, the egg liquid was artificially inoculated to simulate the extreme situation that the egg liquid was contaminated by microorganisms; Stir well to achieve a final Salmonella concentration in the egg wash of about 10 ⁷ cfu/mL.

(3) Sterilization treatment under different stirring speeds: start the system, put the egg liquid into the sterilization kettle, set the sterilization temperature to 28°C, the sterilization pressure to 7Mpa, and the treatment for 10 minutes. During the sterilization process, different stirring speeds are applied respectively. , respectively 0, 50, 100, 150, 200 r/min, to obtain egg liquid processed at different stirring speeds.

(4) Determination of Salmonella lethal logarithm: take the egg liquid treated at different stirring speeds, use the plate counting method to measure the total number of bacterial colonies, and the total number of bacterial colonies in the unsterilized initial egg liquid, according to the following formula, calculate different stirring speeds Logarithmic lethality to Salmonella under high-density CO ₂ treatment: log(n/n ₁ )

where n: the number of microorganisms before sterilization, CFU/mL;

n ₁ : Number of microorganisms after sterilization treatment, CFU/mL

The measurement and calculation results are shown in Table 1.

Table 1 The lethal logarithm of Salmonella by high-density _CO2 treatment at different stirring speeds

stirring speed log lethal to salmonella 0 0.36 50 1.36 100 2.04 150 3.26 200 3.03

As can be seen from Table 1 and Figure 1, when the stirring speed is 0, the sterilization effect is very low, mainly because the CO2 molecules slowly penetrate into the egg liquid under the action of the pressure field and the temperature field, and the _CO2 molecules mainly act on the egg liquid. When the stirring speed is gradually increased, the uniform diffusion of carbon dioxide molecules in the egg liquid is increased, which in turn increases the interaction between carbon dioxide and microorganisms under the action of the pressure field and temperature field, and enhances the sterilization effect. At the same time, increasing agitation can destroy microbial cells, which can greatly enhance the sterilization effect of high-density CO ₂ . According to the experimental results, combined with the effect of stirring treatment on the functional properties of egg liquid, the preferred stirring speed is 50-150rpm.

2. Comparison of killing effects of different egg sterilization methods on Salmonella

2.1 High-density carbon dioxide method

(1) Pretreatment of eggs: take fresh eggs that meet the hygienic standards as raw materials, wash the surface of the egg shell with clean water and air dry, then beat the eggs in a clean environment, take the egg liquid and stir evenly.

(2) High-density carbon dioxide-nested stirring sterilization: put the egg liquid into the sterilization kettle, the sterilization temperature is 30°C, the sterilization pressure is 6Mpa, the treatment is 10min, and the stirring speed is 150rpm.

2.2 High-density carbon dioxide synergistic ultrasonic method

(1) Egg liquid: raw eggs are inspected according to the requirements of "fresh eggs" in the national standard GB2749-2015, and egg liquid is obtained by beating eggs.

(2) High-density carbon dioxide-nested stirring sterilization: put the egg liquid into the sterilization kettle, the sterilization temperature is 30°C, the sterilization pressure is 6Mpa, the treatment is 10min, and the stirring speed is 100rpm.

(3) Aseptic filling: turn on ultraviolet rays and ozone, irradiate and process the material discharge port for 15-30 minutes, and then fill the egg liquid with aseptic containers.

(4) Ultrasonic treatment: The packaged product is placed in an ultrasonic treatment container, the ultrasonic power is 150-220 W/cm ² , and the treatment is performed for 15-25 minutes.

(5) Determination of shelf life: The sterilized egg liquid products are stored under refrigeration (2-10°C) and room temperature (20-25°C), and regular sampling is carried out according to the "liquid egg products" in the national standard GB2749-2015. The indicator determines the shelf life of the product.

(6) Results: Under refrigeration conditions, the shelf life of egg liquid was 30 days; under room temperature conditions, the shelf life of egg white liquid was 15 days.

2.3 High-density carbon dioxide synergistic ultra-high pressure method

(1) Egg liquid: raw eggs are inspected according to the requirements of "fresh eggs" in the national standard GB2749-2015, and egg liquid is obtained by beating eggs.

(2) High-density carbon dioxide-nested stirring sterilization: put the egg liquid into the sterilization kettle, the sterilization temperature is 28°C, the sterilization pressure is 8Mpa, the treatment is 15min, and the stirring speed is 50rpm.

(3) Aseptic filling: turn on ultraviolet rays and ozone, irradiate and process the material discharge port for 15-30 minutes, and then fill the egg liquid with aseptic containers.

(4) Ultra-high pressure treatment: place the packaged product in an ultra-high pressure treatment container, pressurize it to 200-500 MPa for 8-20 minutes, and take it out after releasing the pressure, which is the final product.

(5) Determination of shelf life: The sterilized egg liquid products are stored under refrigeration (2-10°C) and room temperature (20-25°C), and regular sampling is carried out according to the "liquid egg products" in the national standard GB2749-2015. The indicator determines the shelf life of the product.

(6) Results: Under refrigeration conditions, the shelf life of egg liquid was 45 days, and the shelf life of egg liquid at room temperature was 27 days.

2.4 High-density carbon dioxide synergistic ultrasonic and ultra-high pressure method

(1) Egg liquid: raw eggs are inspected according to the requirements of "fresh eggs" in the national standard GB2749-2015, and egg liquid is obtained by beating eggs.

(2) High-density carbon dioxide-nested stirring sterilization: put the egg liquid into the sterilization kettle, the sterilization temperature is 24°C, the sterilization pressure is 4Mpa, the treatment is 5min, and the stirring speed is 150rpm.

(3) Aseptic filling: turn on ultraviolet rays and ozone, irradiate and process the material discharge port for 15-30 minutes, and then fill the egg liquid with aseptic containers.

(4) Ultrasonic treatment: the packaged product is placed in an ultrasonic treatment container, the ultrasonic power is 100-180W/cm ² , and the treatment is performed for 10-18 minutes.

(4) Ultra-high pressure treatment: place the packaged product in an ultra-high pressure treatment container, pressurize it to 100-300 MPa for 5-15 minutes, and take it out after depressurization, which is the final product.

(5) Determination of shelf life: The sterilized egg liquid products are stored under refrigeration (2-10°C) and room temperature (20-25°C), and regular sampling is carried out according to the "liquid egg products" in the national standard GB2749-2015. The indicator determines the shelf life of the product.

(6) Results: Under refrigeration conditions, the shelf life of egg liquid was 95 days, and the shelf life of egg liquid at room temperature was 45 days.

Inoculate Salmonella in fresh egg liquid to compare the killing effect of different treatments on Salmonella.

(1) Pretreatment of eggs: take fresh eggs that meet the hygienic standards as raw materials, wash the surface of the egg shell with clean water and air dry, then beat the eggs in a clean environment, take the egg liquid and stir evenly.

(2) artificially inoculate the egg liquid to simulate the extreme situation that the egg liquid is contaminated by microorganisms; take the activated Salmonella bacteria suspension, add it to the egg liquid in a certain proportion, and stir evenly to make the final Salmonella concentration in the egg liquid. Achieving about 107 ^cfu /mL.

The above technical solutions were used to sterilize the egg liquid (in method 1, the stirring speed was selected to be 150 rpm), and sterilized with ordinary high-density carbon dioxide (without stirring device, other conditions were the same), ultra-high temperature pasteurization (70 The egg liquid treated at ~74°C for 120 s) was used as the control, and the sterilized egg liquid was taken for the determination of the total number of colonies.

The results are shown in Figure 2: the total number of bacteria in the initial contaminated egg liquid was 7.35×10 ⁷ cfu/mL, and after ordinary high-density carbon dioxide treatment and ultra-high temperature pasteurization treatment, the total number of bacteria in the egg liquid was 1.43×10 ⁷ , respectively cfu/mL, 2.39×10 ⁴ cfu/mL, decreased by 3 orders of magnitude; the total number of bacteria in the egg liquid treated by the above four methods is shown in Fig. 2 abscissa 4-7: the total number of bacteria decreased to 1.74×10 ³ cfu/mL (high-density carbon dioxide method), 8.82×10 ² cfu/mL (high-density carbon dioxide synergistic ultrasonic method), 2.38×10 ² cfu/mL (high-density carbon dioxide synergistic ultra-high pressure method), and <10 (high-density carbon dioxide synergistic ultra-high pressure method) Synergistic ultrasonic and ultra-high pressure method), compared with the initial egg liquid, the total number of bacteria was reduced by 4 to 6 orders of magnitude. Therefore, the technical solution of high-density carbon dioxide cooperating with ultrasonic waves and ultra-high pressure can improve the sterilization efficiency of egg liquid by 10 to 1000 times, thereby significantly prolonging the shelf life of egg liquid products.

Example 1

1) Pretreatment of eggs:

Choose fresh eggs that meet hygienic standards, wash the surface of the egg shell with clean water and air dry, then beat the eggs in a clean environment, take the egg liquid and stir it evenly;

2) High-density CO ₂ sterilization treatment:

Put the homogeneous egg liquid into high density CO ₂ , the pressure is 4Mpa, the stirring speed is 50rpm, and the temperature is 24°C for sterilization treatment for 10min, and the ultraviolet rays and ozone are turned on, and then the processed egg liquid is aseptically packaged/aseptically filled. ; get primary products;

3) Ultra-high pressure and ultrasonic co-processing:

The primary product is placed in an ultrasonic treatment container, the ultrasonic power is 100W, and the treatment is 10min; after the ultrasonic treatment is completed, it is placed in an ultra-high pressure sterilization container, pressurized to 50MPa, maintained for 5min, and taken out after decompression, which is the final product 1.

Example 2

1) Pretreatment of eggs:

Choose fresh eggs that meet hygienic standards, wash the surface of the egg shell with clean water and air dry, then beat the eggs in a clean environment, take the egg liquid and stir it evenly;

2) High-density CO ₂ sterilization treatment:

Put the homogeneous egg liquid into high density CO ₂ , the pressure is 6Mpa, the stirring speed is 75rpm, and the temperature is 26℃. ; get primary products;

3) Ultra-high pressure and ultrasonic co-processing:

The primary product was placed in an ultrasonic treatment container, the ultrasonic power was 120W/cm ² , and the treatment was performed for 12 minutes; after the ultrasonic treatment was completed, it was placed in an ultra-high pressure sterilization container, pressurized to 100 MPa, maintained for 10 minutes, and taken out after decompression, that is, for the final product 2.

Example 3

1) Pretreatment of eggs:

Choose fresh eggs that meet hygienic standards, wash the surface of the egg shell with clean water and air dry, then beat the eggs in a clean environment, take the egg liquid and stir it evenly;

2) High-density CO ₂ sterilization treatment:

The uniform egg liquid is placed in high-density CO ₂ , the pressure is 8Mpa, the stirring speed is 100rpm and the temperature is 28°C for sterilization treatment for 20min, and the ultraviolet rays and ozone are turned on, and then the processed egg liquid is aseptically packaged/aseptically filled; obtain primary products;

3) Ultra-high pressure and ultrasonic co-processing:

The primary product is placed in an ultrasonic treatment container, the ultrasonic power is 180W, and the treatment is 12min; after the ultrasonic treatment is completed, it is placed in an ultra-high pressure sterilization container, pressurized to 150MPa, maintained for 8min, and taken out after pressure relief, which is the final product 3.

Example 4

1) Pretreatment of eggs:

Choose fresh eggs that meet hygienic standards, wash the surface of the egg shell with clean water and air dry, then beat the eggs in a clean environment, take the egg liquid and stir it evenly;

2) High-density CO ₂ sterilization treatment:

The uniform egg liquid is placed in high-density CO ₂ , the pressure is 10Mpa, the stirring speed is 150rpm and the temperature is 30°C for sterilization treatment for 25min, the ultraviolet rays and ozone are turned on, and the processed egg liquid is aseptically packaged/aseptically filled; obtain primary products;

3) Ultra-high pressure and ultrasonic co-processing:

The primary product was placed in an ultrasonic treatment container, the ultrasonic power was 180W/cm ² , and the treatment was performed for 18 minutes; after the ultrasonic treatment was completed, it was placed in an ultra-high pressure sterilization container, pressurized to 200 MPa, kept for 15 minutes, and taken out after decompression, that is, for the final product 4.

Comparing the above four sterilization conditions, it is concluded that Example 4 has the best sterilization effect compared with other groups, and the results are shown in Figure 3.

Other parts that are not described in detail are the prior art. Although the above embodiment has made a detailed description of the present invention, it is only a part of the embodiments of the present invention, rather than all the embodiments. People can also obtain other embodiments according to the present embodiment without creativity. These embodiments All belong to the protection scope of the present invention.

Claims (2)

1. a method for cold sterilization and preservation of fresh egg liquid, is characterized in that: comprise the following steps: 1) Pretreatment of eggs: Choose fresh eggs that meet hygienic standards, wash the surface of the egg shell with clean water and air dry, then beat the eggs in a clean environment, take the egg liquid and stir it evenly; 2) High-density CO ₂ sterilization treatment: The uniform egg liquid is placed in high-density CO ₂ , the pressure is 4-10Mpa, the stirring speed is 50-150rpm, and the temperature is 20-30°C for sterilization treatment for 5-15min, and then the processed egg liquid is aseptically packaged/free. Bacteria filling; get primary product; 3) Ultra-high pressure and ultrasonic co-processing: The primary product is placed in an ultrasonic treatment container, the ultrasonic power is 120-180W/cm ² , and the treatment is performed for 12-20 min; 15min, take out after pressure relief, that is the final product. 2. the method for cold sterilization and preservation of fresh egg liquid according to claim 1, is characterized in that: in described step 2), aseptic packaging/aseptic filling: turn on ultraviolet light and ozone, carry out aseptic packaging and aseptic filling Pack.

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