Method for killing bacterial spores in liquid food

Abstract

The application belongs to the technical field of food sterilization, and particularly relates to a method for killing bacterial spores in liquid food. The method comprises the following steps: S1: using an organic acid to adjust the pH value of the liquid food to a predetermined range to obtain pretreated liquid food; S2: placing the pretreated liquid food in a microwave sterilization device, setting parameters of the microwave sterilization device, and using the organic acid in the pretreated liquid food to cooperate with the microwave sterilization device to kill the bacterial spores in the liquid food. The microwave electromagnetic field is used to disturb the cell membrane potential of the bacterial spores, so that the cell membrane generates physical pores or breaks, and hydrogen ions can act on the inside of the bacterial spores, so that the bacterial spores can be effectively killed at a lower temperature, and the destruction of high temperature on heat-sensitive nutrients and sensory quality in the liquid food is avoided.

Description

Technical Field

[0001] This invention belongs to the field of food sterilization technology, specifically relating to a method for killing bacterial spores in liquid food. Background Technology

[0002] Bacterial spores are highly dormant, multi-layered physiological structures formed by bacteria through cell differentiation when nutrients are scarce or environmental conditions are harsh. Compared to ordinary vegetative cells, spores exhibit extremely strong resistance, tolerating drying, ultrasound, ultra-high pressure, high temperatures, and various chemical bactericides. Currently, industrial methods primarily employ heat sterilization of bacterial spores, reaching temperatures exceeding 100°C. However, such high temperatures can severely damage the nutritional and sensory quality of food. Therefore, reducing the temperature required for spore sterilization is a crucial issue of concern in the food science community.

[0003] For example, the prior art patent application number 200910001170.0, entitled "Method for Sterilizing Liquid and Liquid Food," provides the following technical solution: A high electric field pulse with a pulse width of less than 200 ns, a pulse rise time of less than 50 ns, and an electric field strength of 10–200 kV / cm is applied to the liquid food material to heat the material to a predetermined temperature of at least 100°C. The liquid food material has an electrical conductivity of 30–1000 mS / m, and the time required to heat it to the predetermined temperature is less than 10 seconds; after heating to the predetermined temperature, it is cooled within 300 seconds.

[0004] In the aforementioned prior art, liquid food is heated to 100-160°C within 10 seconds by applying a high electric field pulse to it, thereby killing bacterial spores in the liquid food. However, the following technical problems still exist: when liquid food is heated to 100-160°C by a high electric field pulse, the heat-sensitive nutrients in the liquid food will degrade and become inactive due to the excessively high temperature, and the liquid food will undergo browning due to the excessively high temperature, ultimately resulting in the destruction of the heat-sensitive nutrients and sensory quality of the liquid food. Summary of the Invention

[0005] In view of this, the present invention provides a method for killing bacterial spores in liquid food, which reduces the temperature required to kill bacterial spores and avoids the damage of heat-sensitive nutrients and sensory quality in liquid food caused by high temperature.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A method for killing bacterial spores in liquid food includes the following steps:

[0008] S1: Use organic acids to adjust the pH value of liquid food to a predetermined range to obtain pretreated liquid food;

[0009] S2: Place the pre-treated liquid food in a microwave sterilization device, set the parameters of the microwave sterilization device, and use the organic acids in the pre-treated liquid food to sterilize in synergy with the microwave sterilization device to kill bacterial spores in the liquid food. The microwave electromagnetic field generated by the microwave sterilization device disturbs the cell membrane potential of the bacterial spores, causing physical pores or ruptures on the cell membrane, so that the hydrogen ions of the organic acids can act on the inside of the bacterial spores. The sterilization effect can be achieved without heating the liquid food to above 100°C.

[0010] Preferably, the organic acid in step S1 is any one of citric acid, tartaric acid, or malic acid.

[0011] Preferably, the predetermined pH range in step S1 is pH 2 to 4.

[0012] Preferably, the liquid food in step S1 includes any one of fruit and vegetable pulp, fruit and vegetable juice, dairy products, or beverages.

[0013] Preferably, the parameters of the microwave sterilization device in step S2 are: temperature 60~80℃ and microwave power 600~1000W.

[0014] Preferably, the microwave sterilization device in step S2 is any one of the following: box-type microwave sterilization equipment, tunnel-type microwave sterilization equipment, pipeline-type microwave sterilization equipment, drum-type microwave sterilization equipment, and tank-type microwave sterilization equipment.

[0015] Preferably, when the liquid food is coconut water, the microwave sterilization device in step S2 is set with the following parameters: temperature 60~80℃, microwave power 750~850W, and sterilization time 15~25min.

[0016] Preferably, when the liquid food is watermelon juice, the microwave sterilization device in step S2 is set with the following parameters: temperature 60~80℃, microwave power 650~750W, and sterilization time 25~35min.

[0017] Preferably, when the liquid food is milk, the microwave sterilization device in step S2 is set with the following parameters: temperature 60~80℃, microwave power 850~950W, and sterilization time 15~25min.

[0018] In the above-mentioned method for killing bacterial spores, organic acids are used to adjust the hydrogen ion concentration of liquid food, and then a microwave sterilization device is used to kill bacterial spores in the pretreated liquid food. The microwaves generated by the microwave sterilization device destroy the cell membrane of the bacterial spores, so that the hydrogen ions of the organic acid can act on the inside of the bacterial spores. The sterilization effect can be achieved without heating the liquid food to above 100°C. Detailed Implementation

[0019] To better understand the present invention, the present invention will be further described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments.

[0020] A method for killing bacterial spores in liquid food includes the following steps:

[0021] S1: Adjust the pH value of liquid food to a predetermined range using organic acid to obtain pretreated liquid food, wherein the organic acid is any one of citric acid, tartaric acid or malic acid, the predetermined pH value range is pH 2 to 4, and the liquid food includes any one of fruit and vegetable pulp, fruit and vegetable juice, dairy products or beverages.

[0022] S2: Place the pretreated liquid food in a microwave sterilization device, set the microwave sterilization device parameters to 60~80℃ and 600~1000W, utilize the organic acids in the pretreated liquid food and the microwave sterilization device to synergistically sterilize, thereby killing bacterial spores in the liquid food. Specifically, the microwave electromagnetic field generated by the microwave sterilization device disturbs the cell membrane potential of the bacterial spores, causing physical pores or ruptures on the cell membrane, allowing the hydrogen ions of the organic acids to act on the inside of the bacterial spores, thus achieving a sterilization effect even at a lower temperature. The microwave sterilization device can be any one of the following: box-type microwave sterilization equipment, tunnel-type microwave sterilization equipment, pipeline-type microwave sterilization equipment, drum-type microwave sterilization equipment, or tank-type microwave sterilization equipment.

[0023] Furthermore, when the liquid food is coconut water, the microwave sterilization device in step S2 is set with the following parameters: temperature 60~80℃, microwave power 750~850W, and sterilization time 15~25min.

[0024] Furthermore, when the liquid food is watermelon juice, the microwave sterilization device in step S2 is set with the following parameters: temperature 60~80℃, microwave power 650~750W, and sterilization time 25~35min.

[0025] Furthermore, when the liquid food is milk, the microwave sterilization device in step S2 is set with the following parameters: temperature 60~80℃, microwave power 850~950W, and sterilization time 15~25min.

[0026] To facilitate understanding of the technical concept and patentability of this application, the following embodiments are further provided:

[0027] Example 1

[0028] This embodiment provides a method for killing bacterial spores in coconut water, including the following steps:

[0029] S1: Use citric acid to adjust the pH of coconut water to 2 and adjust the bacterial spore count of coconut water to 7 1g CFU / mL to obtain pretreated coconut water;

[0030] S2: Place the pretreated coconut water in a box-type microwave sterilization device, set the microwave power to 800 W, the temperature to 70℃, and the time to 20 minutes to start sterilization and obtain sterilized coconut water.

[0031] Example 2

[0032] This embodiment provides a method for killing bacterial spores in watermelon juice, including the following steps:

[0033] S1: Adjust the pH of watermelon juice to 3 using malic acid, and adjust the bacterial spore count of watermelon juice to 7 1g CFU / mL to obtain pretreated watermelon juice;

[0034] S2: Place the pre-treated watermelon juice in a box-type microwave sterilization device, set the microwave power to 700 W, the temperature to 70℃, and the time to 30 minutes, and start sterilization to obtain sterilized watermelon juice.

[0035] Example 3

[0036] This embodiment provides a method for killing bacterial spores in milk, including the following steps:

[0037] S1: Use tartaric acid to adjust the pH of the milk to 4 and adjust the bacterial spore count of the milk to 7 1g CFU / mL to obtain pretreated milk;

[0038] S2: Place the pretreated milk in a box-type microwave sterilizer, set the microwave power to 900 W, the temperature to 70℃, and the time to 20 minutes, and start sterilization to obtain sterilized milk.

[0039] Comparative Example 1

[0040] This embodiment provides a method for killing bacterial spores in coconut water, including the following steps:

[0041] S1: The pH of the coconut water was not adjusted using organic acids, and the bacterial spore count of the coconut water was adjusted to 7 lg CFU / mL;

[0042] S2: Place the coconut water in a box-type microwave sterilization device, set the microwave power to 800 W, the temperature to 70℃, and the time to 20 minutes to start sterilization and obtain sterilized coconut water.

[0043] Comparative Example 2

[0044] This embodiment provides a method for killing bacterial spores in watermelon juice, including the following steps:

[0045] S1: Adjust the pH of watermelon juice to 3 using malic acid, and adjust the bacterial spore count of watermelon juice to 7 1g CFU / mL to obtain pretreated watermelon juice;

[0046] S2: Place the pretreated watermelon juice in a water bath heating device at a temperature of 70℃ for 30 minutes to start sterilization and obtain sterilized watermelon juice.

[0047] Comparative Example 3

[0048] This embodiment provides a method for killing bacterial spores in milk, including the following steps:

[0049] S1: The pH of the milk was not adjusted using organic acids, and the number of bacterial spores in the milk was adjusted to 7 1g CFU / mL;

[0050] S2: Place the milk in a water bath heating device at a temperature of 80℃ for 20 minutes to begin sterilization, thus obtaining sterilized milk.

[0051] Table 1

[0052] As shown in Table 1 above, in Example 1, the microwave power, heating temperature, and time were exactly the same as in Comparative Example 1, and the number of bacterial spores before killing was 7 1g CFU / mL. The pH of the coconut water was lowered from 5.6 to 2.0. The results showed that the number of bacterial spores killed in Example 1 was 3.12 1g CFU / mL, while the number killed in Comparative Example 1 was 0.68 1g CFU / mL, representing a logarithmic improvement in sterilization effect of 4.59 times. In Example 2, under the same acidic environment, temperature, and time conditions, the number of bacterial spores before killing was 7 1g CFU / mL. The results showed that the number of bacterial spores killed in Example 2 was 3.07 1g CFU / mL, while the number killed in Comparative Example 2 was 0.39 1g CFU / mL. The logarithmic sterilization effect of the combined microwave treatment in Example 2 was 7.87 times that of conventional heating at 80℃ in Comparative Example 2. Compared with Comparative Example 3, Example 3 lowered the pH of milk to 4.0 by adding tartaric acid and sterilized it with microwave at 70°C for 20 minutes. In Comparative Example 3, the pH of milk was not adjusted and it was sterilized by heating to 80°C in a conventional water bath for 20 minutes. The results showed that the number of bacterial spores killed in Example 3 was 1.95 lg CFU / mL. Although the temperature in Comparative Example 3 was higher, the number of bacterial spores killed was only 0.04 lg CFU / mL. The logarithmic sterilization effect of Example 3 was 48.75 times that of Comparative Example 3.

[0053] In summary, the above conclusions fully demonstrate that the non-thermal effect of microwaves and the hydrogen ions of organic acids produce a synergistic bactericidal effect. The mechanism lies in the fact that the microwave electromagnetic field generated by the microwave sterilization device disrupts the cell membrane potential of bacterial spores, leading to physical pores or ruptures in the cell membrane. This allows the hydrogen ions of organic acids to act on the interior of the bacterial spores, and the synergistic effect of the non-thermal microwave effect and the organic acids can kill bacterial spores at relatively low temperatures.

[0054] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for killing bacterial spores in liquid food, characterized in that, Includes the following steps: S1: Use organic acids to adjust the pH value of liquid food to a predetermined range to obtain pretreated liquid food; S2: Place the pre-treated liquid food in a microwave sterilization device, set the parameters of the microwave sterilization device, and use the organic acids in the pre-treated liquid food to work together with the microwave sterilization device to kill bacterial spores in the liquid food. The microwave electromagnetic field generated by the microwave sterilization device disturbs the cell membrane potential of the bacterial spores, causing physical pores or ruptures on the cell membrane, so that the hydrogen ions of the organic acids can act on the inside of the bacterial spores. The sterilization effect can be achieved without heating the liquid food to above 100°C.

2. The method for killing bacterial spores in liquid food according to claim 1, characterized in that, The organic acid mentioned in step S1 is any one of citric acid, tartaric acid, or malic acid.

3. The method for killing bacterial spores in liquid food according to claim 1, characterized in that, The predetermined pH range mentioned in step S1 is pH 2 to 4.

4. The method for killing bacterial spores in liquid food according to claim 1, characterized in that, The liquid food mentioned in step S1 includes any one of fruit and vegetable pulp, fruit and vegetable juice, dairy products, or beverages.

5. The method for killing bacterial spores in liquid food according to claim 1, characterized in that, The parameters of the microwave sterilization device mentioned in step S2 are: temperature 60~80℃ and microwave power 600~1000W.

6. The method for killing bacterial spores in liquid food according to claim 1, characterized in that, The microwave sterilization device mentioned in step S2 is any one of the following: box-type microwave sterilization equipment, tunnel-type microwave sterilization equipment, pipeline-type microwave sterilization equipment, drum-type microwave sterilization equipment, and tank-type microwave sterilization equipment.

7. The method for killing bacterial spores in liquid food according to claim 1, characterized in that, When the liquid food is coconut water, the microwave sterilization device in step S2 is set with the following parameters: temperature 60~80℃, microwave power 750~850W, and sterilization time 15~25min.

8. The method for killing bacterial spores in liquid food according to claim 1, characterized in that, When the liquid food is watermelon juice, the microwave sterilization device in step S2 is set with the following parameters: temperature 60~80℃, microwave power 650~750W, and sterilization time 25~35min.

9. The method for killing bacterial spores in liquid food according to claim 1, characterized in that, When the liquid food is milk, the microwave sterilization device in step S2 is set with the following parameters: temperature 60~80℃, microwave power 850~950W, and sterilization time 15~25min.

Images