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Photodynamic killing method of listeria monocytogenes in liquid milk

A monoproliferative Listeria monocytogenes, photodynamic technology, applied in the preservation of milk, dairy products, applications, etc., to achieve the effect of good application prospects, wide sources, and no drug resistance

Inactive Publication Date: 2018-11-13
JINAN UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

As a new non-thermal sterilization technology-photodynamic technology is applied in the field of food safety, there are few reports at home and abroad, and there are no reports of photodynamic technology as a method of killing Listeria monocytogenes in milk at home and abroad

Method used

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  • Photodynamic killing method of listeria monocytogenes in liquid milk
  • Photodynamic killing method of listeria monocytogenes in liquid milk

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0033] Embodiment 1. Methylene blue concentration experiment

[0034] (1) Pre-treatment with experimental strains

[0035] Inoculate Listeria monocytogenes into nutrient agar medium, pick a single colony, and after activation, cultivate it in a tryptone soybean broth medium on a shaker, shake it at 37°C until the logarithmic growth phase, and collect the bacteria by centrifugation (4000r / min, 10min), discard the supernatant, and suspend the bacteria in PBS; prepare the milk bacteria suspension so that the concentration of the milk bacteria suspension is 10 8 About CFU / mL.

[0036] (2) photosensitizer concentration treatment

[0037]Dilute methylene blue with PBS to prepare different concentrations of methylene blue solutions, then add the methylene blue solution to 200 μL milk bacteria suspension in a 96-well plate, so that the final concentrations of methylene blue are 0.005, 0.05, 0.2, 0.5, 1, 2 , 5 and 10 μg / mL. Incubate at 37°C in the dark for 30 min, place it at a di...

Embodiment 2

[0039] Embodiment 2. Lighting time experiment

[0040] (1) Pre-treatment with experimental strains

[0041] Inoculate the Listeria monocytogenes species into the nutrient agar medium, pick a single colony, and culture it in the tryptone soybean broth medium after activation, shake it at 37°C until the logarithmic growth phase, and collect the bacteria by centrifugation (4000r / min, 10min), discard the supernatant, and suspend the bacteria in PBS; prepare the milk bacteria suspension so that the concentration of the milk bacteria suspension is 10 8 About CFU / mL.

[0042] (2) Illumination time processing

[0043] Contain 200 μL of milk bacteria suspension in a 96-well plate, and add methylene blue to make the final concentration 2 μg / mL, incubate at 37°C for 30 minutes in the dark, and then act under the irradiation intensity of 160 mW for 1, 5, 10, 15, 20 and 30 minutes Then carry out the plate count (L+S+). At the same time set no light and \ or no MB group as a control (L...

Embodiment 3

[0045] Example 3. Method for Determination of Effects Before and After Photodynamic Sterilization of Listeria monocytogenes in Milk

[0046] The bacterial suspensions obtained by different treatment methods were all serially diluted 1:10, and 100 μL was taken out and plated on a plate of bacterial counting medium, incubated at a constant temperature in a biochemical incubator at 37°C, and taken out after 24 hours for colony counting. In order to make the diagram clearer, the experimental results are expressed in log CFU / mL, and a bar graph is drawn. The experiment was repeated 3 times and the average value was taken.

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PUM

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Abstract

The invention belongs to the technical field of microorganism sterilizing, and discloses a photodynamic killing method of listeria monocytogenes in liquid milk. According to the method, a bromine tungsten lamp is used as a light source, methylene blue is used as a photosensitizer, a non-thermal photodynamic sterilization technique is used for killing the listeria monocytogenes in the milk. The photodynamic killing method disclosed by the invention has the following advantages that the used photosensitizer namely the methylene blue has good light-sensitive activity, and easily infiltrates intotissue cells, the wave length range is broad, and the methylene blue is suitable for different light sources and is free from obvious toxin, broad in source and low in price; the sterilizing method ishigh in safety, high in efficiency, environmental-friendly, quick and convenient, bacteria cannot generate drug tolerance, and the sterilizing method can be reused; the non-thermal photodynamic sterilization method can kill the listeria monocytogenes in the liquid milk, and can guarantee the milk quality to the maximum extent, so that the loss of thermal-sensitive nutrient components and volatileflavor substances can be greatly reduced.

Description

technical field [0001] The invention belongs to the technical field of microorganism sterilization, and relates to a food sterilization method, in particular to a photodynamic method for killing Listeria monocytogenes in liquid milk. Background technique [0002] Listeria monocytogenes (Listeria monocytogenes) referred to as Listeria monocytogenes, Listeria monocytogenes is a facultative anaerobic Gram-positive short bacilli, is the most important human food in the Listeria genus In the 1990s, it was listed as one of the four major pathogenic bacteria in food. After it infects humans, the mortality rate is as high as 25%, while for immunocompromised patients, the mortality rate is even as high as 70%. Contamination of Listeria monocytogenes is prone to occur in milk and dairy products. The detection of Listeria monocytogenes in ice cream in Jiangsu and Beijing in my country shows that the contamination rate is 2.2-7.3%. Milk sterilization methods include pasteurization and ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): A23C3/07
CPCA23C3/07
Inventor 唐书泽吴希阳杨璐环林少玲
Owner JINAN UNIVERSITY
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