Preparation method of edible photosensitizer with high bactericidal performance and application of edible photosensitizer in removal of harmful bacteria on contact surface of food device

Abstract

The invention belongs to the technical field of non-thermal technology sterilization, and particularly relates to a preparation method of an edible photosensitizer with high sterilization performance and application of the edible photosensitizer in harmful bacterium removal of a contact surface of a food device, and the preparation method comprises the following steps: step 1, dissolving curcumin with absolute ethyl alcohol to obtain a curcumin stock solution; dissolving octyl gallate with absolute ethyl alcohol to obtain an octyl gallate stock solution; step 2, obtaining a chitosan solution; step 3, uniformly mixing the curcumin stock solution and the chitosan solution to obtain a curcumin-chitosan solution; and step 4, taking the curcumin-chitosan solution, putting the curcumin-chitosan solution into a glass container, and adding the octyl gallate stock solution and the chitosan solution in volume parts. The invention also discloses application of the edible photosensitizer with high bactericidal performance in killing bacteria in food and carrying out photodynamic sterilization on food contact surfaces. The method is short in sterilization treatment time, green, free of pollution and easy to directly apply in the food industry.

Description

Technical Field

[0001] The invention belongs to the technical field of non-thermal sterilization, and specifically relates to a preparation method of an edible photosensitizer with high bactericidal performance and its application in removing harmful bacteria on the contact surface of food equipment. Background Art

[0002] Common materials for food processing equipment contact surfaces include stainless steel, glass, polyvinyl chloride, etc. Food contact materials are susceptible to microbial contamination and cross-contamination with food during deep processing and cold chain logistics transportation, which can cause food spoilage and threaten human health. Sterilization of food processing contact surfaces is a front-end step to prevent food from being contaminated. In order to avoid the impact of traditional chemical sterilization on food safety and control costs, a safe new food contact surface sterilization technology is of great significance to ensure food safety.

[0003] In the specific prior art, chemical agents such as quaternary ammonium disinfectants and chlorine-containing disinfectants are used to disinfect the surface of food contact materials. However, long-term use of chemical disinfectants to eliminate or inactivate pathogens may lead to potential toxicity, corrosiveness or volatility problems; physical technologies such as ultraviolet sterilization pose potential threats to food and humans; traditional disinfectants will gradually reduce their effectiveness against bacterial cells and some environments where organic matter exists; traditional photosensitizers such as curcumin-mediated PDI have low bactericidal efficacy and cannot meet the use requirements, and the widespread use of disinfectants has an adverse impact on the environment; long-term chemical treatment can easily make bacteria resistant and thus give rise to super bacteria, and chemical residues on food contact surfaces threaten food safety and human health; natural photosensitizers such as curcumin have low bioavailability and unstable interference with the efficiency of photodynamic inactivation.

[0004] However, among the emerging sterilization and disinfection methods, photodynamic inactivation (PDI) is a new non-thermal sterilization technology with low energy consumption, no chemical residue, and no pollution to the environment. It consists of photosensitizer, oxygen and light source. PDI relies on the photosensitizer to be stimulated by the light source to produce reactive oxygen and then cause oxidative damage to microorganisms. PDI is an emerging technology in the food field. Studies have shown that PDI has a good inhibitory effect on typical pathogens and spoilage bacteria such as Escherichia coli, Staphylococcus aureus, Pseudomonas, and Thermomyces. New and efficient photosensitizers are the key factors to improve the efficiency of photodynamic inactivation. However, photodynamic sterilization technology also has limitations in practical applications because of the low bactericidal efficiency and bioavailability of the photosensitizer itself, and the different absorption peaks of different photosensitizers. In addition, in practical applications, it is necessary to consider issues such as the sample itself, the actual application form and safety. Curcumin is a natural plant polyphenol and a safe food additive allowed for use in accordance with the national standard GBB2760-2021. Studies have shown that curcumin can produce reactive oxygen in response to light, causing oxidative damage to microorganisms, and effectively inhibit foodborne bacteria such as Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes. Light-responsive films and coatings prepared with curcumin as raw materials also have the effect of extending the shelf life of fruits, vegetables, and meat products. Octyl gallate is an alkyl derivative of gallic acid, a natural phenolic acid substance. It is a food additive for oils and lipid-rich foods approved for use by the U.S. Food and Drug Administration, the Food and Agriculture Organization of the United Nations, and the World Health Organization. Octyl gallate can be used as a preservative in food, and studies have shown that it can be used to preserve products such as apple juice and oyster meat. Chitosan is a safe food additive allowed for use in accordance with the national standard GBB2760-2021. It is an excellent raw material for making food packaging and biological preservatives. It has an excellent film-forming mechanism and is widely used in food.

[0005] Therefore, how to overcome the application limitations of photosensitizers themselves and develop a new type of photosensitizer to improve PDI efficiency and improve the killing effect of harmful bacteria in food contact surfaces is an urgent problem to be solved. Summary of the invention

[0006] The purpose of the present invention is to provide a preparation method of an edible photosensitizer with high bactericidal performance and its application in removing harmful bacteria on the contact surface of food devices. A new photosensitizer is prepared by using curcumin, octyl gallate and chitosan as raw materials to improve the efficiency of PDI. The new photosensitizer can have a broad-spectrum antibacterial property, be safe, non-toxic, low-cost, and effectively remove harmful bacteria on the contact surface of food, thereby ensuring the safety of food processing.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for preparing an edible photosensitizer with high bactericidal performance comprises the following steps:

[0009] Step 1: Curcumin was dissolved in anhydrous ethanol to obtain a 1 mmol / L curcumin stock solution; octyl gallate was dissolved in anhydrous ethanol to obtain a 1 mmol / L octyl gallate stock solution;

[0010] Step 2: adding chitosan to a 1% acetic acid solution to obtain a 0.5% chitosan solution;

[0011] Step 3: taking a curcumin stock solution and a chitosan solution in a volume ratio of 0.5-2:20-30 parts and mixing them evenly to obtain a curcumin-chitosan solution;

[0012] Step 4: Take 20-30 parts by volume of the curcumin-chitosan solution in a glass container, add 3-4 parts by volume of the octyl gallate stock solution and 4-5 parts by volume of the chitosan solution, and mix them to obtain an edible photosensitizer with high bactericidal performance.

[0013] Preferably, the concentration of curcumin in the edible photosensitizer with high bactericidal performance is 12-70 μmol / L, and the concentration of octyl gallate is 75-150 μmol / L.

[0014] The invention discloses an application of an edible photosensitizer with high bactericidal performance in killing bacteria in food, characterized in that: the photosensitizer is a photosensitizer prepared by a method for preparing an edible photosensitizer with high bactericidal performance; the photosensitizer is sprayed on the surface of food, and then LED visible light is used for irradiation for a certain period of time to kill the bacteria in the food.

[0015] Preferably, the bacteria in food that can be killed include: Escherichia coli, Staphylococcus aureus, Pseudomonas fragariae and Thermotrichum thermophilum; when the LED visible light is irradiated, the wavelength of the LED visible light is 450nm and the output power is 6mW / cm 2 The irradiation time is 20-30min and the irradiation distance is 15cm.

[0016] A high-bactericidal edible photosensitizer is used in photodynamic sterilization of food contact surfaces. The photosensitizer is prepared by a method for preparing a high-bactericidal edible photosensitizer. The photosensitizer is sprayed on the food contact surface and then irradiated with LED visible light for a certain period of time to kill bacteria on the food contact surface.

[0017] Preferably, the food contact surface includes a stainless steel surface, a glass surface and a plastic surface; when the LED visible light is irradiated, the wavelength of the LED visible light is 450nm and the output power is 6mW / cm 2 The irradiation time is 20-30min and the irradiation distance is 15cm.

[0018] The technical effects achieved by the present invention are:

[0019] In the present invention, curcumin, octyl gallate and chitosan are used as raw materials to prepare a new photosensitizer, which improves the efficiency of PDI. The new photosensitizer can have a broad-spectrum antibacterial property, is safe, non-toxic, low-cost, and can effectively remove harmful bacteria on the food contact surface, thereby ensuring the safety of food processing.

[0020] The purpose of the present invention is to provide a method for preparing a novel photosensitizer prepared from curcumin, octyl gallate and chitosan as raw materials and a strategy for effective sterilization of food contact surfaces, so as to solve the existing problems of traditional technologies. The novel photosensitizer solves the problems of poor water solubility and insufficient bactericidal efficacy of curcumin, has excellent killing efficacy against both Gram-negative and Gram-positive bacteria, can greatly improve the bactericidal efficiency, and has broad-spectrum antibacterial properties.

[0021] In the present invention, curcumin, octyl gallate and chitosan are used to prepare a novel photosensitizer, which improves the problems of poor water solubility and insufficient bactericidal efficacy of curcumin. Octyl gallate and curcumin can synergistically provide more efficient bactericidal efficacy, and chitosan can improve the water solubility and bactericidal efficacy of curcumin and octyl gallate. The inherent limitations of existing photosensitizers are solved.

[0022] Curcumin and chitosan are both safe food additives allowed for use in accordance with GBB2760-2021. Octyl gallate is a food additive for oils and lipid-rich foods approved for use by the Food and Agriculture Organization of the United Nations and the World Health Organization.

[0023] The new photosensitizer has a strong killing effect on Gram-negative bacteria and Gram-positive bacteria. As the illumination time increases, the bactericidal effect is significantly enhanced, and it has a stronger killing effect on Gram-positive bacteria. It can remove Gram bacteria that are difficult to remove on food contact surfaces to ensure food safety.

[0024] In general, the present invention is simple and convenient, has a short processing time, is low in cost, is green and pollution-free, is easy to be directly applied in the food industry, and has certain control and prevention effects, thus providing strong technical support for maintaining public health. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The above graph shows the ability of various substances to eliminate Escherichia coli at different irradiation times in Experimental Example 1 of the present invention.

[0026] Figure 2 The figure shows the ability of each substance to eliminate Pseudomonas fragariae at different irradiation times in Experimental Example 2 of the present invention.

[0027] Figure 3 The above is the ability of each substance to eliminate Staphylococcus aureus at different irradiation times in Experimental Example 3 of the present invention.

[0028] Figure 4The clearance ability of each substance against thermocidal Trichoderma at different irradiation times in Experimental Example 4 of the present invention is shown.

[0029] Figure 5 This is the ability to remove E. coli on different contact surfaces in Experimental Example 5 of the present invention.

[0030] Figure 6 This is the ability to remove Pseudomonas fragariae on different contact surfaces in Experimental Example 6 of the present invention.

[0031] Figure 7 This is the ability to remove Staphylococcus aureus on different contact surfaces in Experimental Example 7 of the present invention.

[0032] Figure 8 This is the ability of removing heat-killed Trichoderma on different contact surfaces in Experimental Example 8 of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose and advantages of the present invention more clearly understood, the present invention is specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific embodiments of the present invention, and does not strictly limit the scope of protection of the specific claims of the present invention.

[0034] Embodiment 1:

[0035] A method for preparing an edible photosensitizer with high bactericidal performance comprises the following steps:

[0036] Step 1: Curcumin was dissolved in anhydrous ethanol to obtain a 1 mmol / L curcumin stock solution; octyl gallate was dissolved in anhydrous ethanol to obtain a 1 mmol / L octyl gallate stock solution;

[0037] Step 2: adding chitosan to a 1% acetic acid solution to obtain a 0.5% chitosan solution;

[0038] Step 3: taking a curcumin stock solution and a chitosan solution in a volume ratio of 0.5-2:20-30 parts and mixing them evenly to obtain a curcumin-chitosan solution;

[0039] Step 4: Take 20-30 parts by volume of the curcumin-chitosan solution in a glass container, add 3-4 parts by volume of the octyl gallate stock solution and 4-5 parts by volume of the chitosan solution, and mix them to obtain an edible photosensitizer with high bactericidal performance.

[0040] Among them, the concentration of curcumin in the edible photosensitizer with high bactericidal performance is 12-70 μmol / L, and the concentration of octyl gallate is 75-150 μmol / L.

[0041] As the best embodiment, in the actual manufacture of an edible photosensitizer with high bactericidal performance: first: curcumin is dissolved in anhydrous ethanol to obtain a 1mmol / L curcumin stock solution; octyl gallate is dissolved in anhydrous ethanol to obtain a 1mmol / L octyl gallate stock solution; then: chitosan is added to a 1% acetic acid solution to obtain a 0.5% chitosan solution; then: 1mL of curcumin stock solution is added to 24mL of chitosan solution and mixed evenly to obtain a curcumin-chitosan solution, 24mL of curcumin-chitosan solution is taken in a glass container, 3.2mL of octyl gallate stock solution and 4.8mL of chitosan solution are added, and the edible photosensitizer with high bactericidal performance is obtained by mixing, wherein the curcumin concentration in the edible photosensitizer with high bactericidal performance is 30μmol / L, and the octyl gallate concentration is 100μmol / L.

[0042] Embodiment 2:

[0043] The invention discloses an application of an edible photosensitizer with high bactericidal performance in killing bacteria in food, characterized in that: the photosensitizer is a photosensitizer prepared by a preparation method of an edible photosensitizer with high bactericidal performance; the photosensitizer is sprayed on the surface of food, and then LED visible light is used for irradiation for a certain period of time to kill the bacteria in the food.

[0044] Preferably, the bacteria in food that can be killed include: Escherichia coli, Staphylococcus aureus, Pseudomonas fragariae and Thermotrichum thermophilum; when the LED visible light is irradiated, the wavelength of the LED visible light is 450nm and the output power is 6mW / cm 2 The irradiation time is 20-30min and the irradiation distance is 15cm.

[0045] Embodiment three:

[0046] A high-bacterial-performance edible photosensitizer is used in photodynamic sterilization of food contact surfaces. The photosensitizer is prepared by a method for preparing a high-bacterial-performance edible photosensitizer. The photosensitizer is sprayed on the food contact surface and then irradiated with LED visible light for a certain period of time to kill bacteria on the food contact surface.

[0047] Preferably, the food contact surface includes a stainless steel surface, a glass surface and a plastic surface; when the LED visible light is irradiated, the wavelength of the LED visible light is 450nm and the output power is 6mW / cm 2 The irradiation time is 20-30min and the irradiation distance is 15cm.

[0048] Comparative Example 1:

[0049] The 0.5% chitosan solution was directly prepared without adding curcumin and octyl gallate.

[0050] Comparative Example 2:

[0051] The difference between this comparative example and the preferred embodiment in Example 1 is that in the step of preparing the novel photosensitizer, octyl gallate is not added, and 1 mmol / L of curcumin stock solution is dissolved with 0.5% chitosan solution to a final concentration of curcumin of 30 μmol / L to obtain a curcumin solution containing 0.5% chitosan as the solvent.

[0052] Comparative Example 3:

[0053] The difference between this comparative example and the preferred embodiment in Example 1 is that in the step of preparing the novel photosensitizer, curcumin is not added, and a 1 mmol / L octyl gallate stock solution is dissolved with a 0.5% chitosan solution to a final concentration of octyl gallate of 100 μmol / L, to obtain an octyl gallate solution containing 0.5% chitosan as the solvent.

[0054] Experimental Example 1:

[0055] First, E. coli was activated and cultured at 37°C for 36 hours. The photosensitizer prepared according to the best embodiment of Example 1 was mixed with the E. coli solution at a ratio of 2:1. The blank control was a mixture of 0.9% saline and the E. coli solution at a ratio of 2:1. After incubation for 20 minutes, the mixture was kept in the dark or at 6 mW / cm 2 Irradiate with high-intensity 450nm visible light for 0-30min at a distance of 15cm. Spread 100μL of each sample after gradient dilution on tryptic soy agar medium and incubate at 37℃ for 12h. Count the colonies, with 2 parallels for each group.

[0056] Then, the solutions of Comparative Example 1, Comparative Example 2 and Comparative Example 3 were used to conduct comparative experiments in the same manner as above, and the experimental results were as follows: Figure 1 shown.

[0057] from Figure 1 It can be seen that the total number of E. coli in the blank control, comparative example 1 has almost no effect on E. coli and does not change with the change of illumination time. Comparative examples 2 and 3 have an increased inhibitory effect on E. coli with the illumination time, but cannot completely kill E. coli. The photosensitizer prepared by the optimal implementation in Example 1 has a strong inhibitory effect, and E. coli can be completely eliminated in 20 minutes, which has better antibacterial performance than comparative examples 1, 2 and 3.

[0058] Experimental Example 2:

[0059] First, activate Pseudomonas fragariae and culture at 30°C for 36 hours. Mix the photosensitizer prepared according to the best embodiment of Example 1 with the bacterial solution of Pseudomonas fragariae at a ratio of 2:1. The blank control is a mixture of 0.9% saline and the bacterial solution of Pseudomonas fragariae at a ratio of 2:1. After incubation for 20 minutes, keep the mixture in the dark or at 6 mW / cm 2 Irradiate with high-intensity 450nm visible light for 0-30min, with an illumination distance of 15cm. Pipette 100μL of each sample after gradient dilution and spread it on tryptic soy peptone agar medium, incubate at 30℃ for 24h, and count the colonies, with 2 parallels for each group.

[0060] Then, the solutions of Comparative Example 1, Comparative Example 2 and Comparative Example 3 were used to conduct comparative experiments in the same manner as above, and the experimental results were as follows: Figure 2 shown.

[0061] from Figure 2 It can be seen that the total number of Pseudomonas fragariae in the blank control, comparative example 1 has almost no effect on Pseudomonas fragariae and does not change with the change of illumination time. Comparative examples 2 and 3 have increased inhibitory effects on Escherichia coli with the illumination time, but cannot completely kill Pseudomonas fragariae. The photosensitizer prepared by the optimal implementation method in Example 1 has a strong inhibitory effect, and Pseudomonas fragariae can be completely eliminated in 30 minutes, which has better antibacterial performance than comparative examples 1, 2 and 3.

[0062] Experimental Example 3:

[0063] First, Staphylococcus aureus was activated and cultured at 37°C for 36 hours. The photosensitizer prepared according to the best embodiment of Example 1 was mixed with Staphylococcus aureus solution at a ratio of 2:1. The blank control was a mixture of 0.9% saline and Staphylococcus aureus solution at a ratio of 2:1. After incubation for 20 minutes, the mixture was kept in the dark or at 6 mW / cm 2 Irradiate with high-intensity 450nm visible light for 0-30min at a distance of 15cm. Spread 100μL of each sample after gradient dilution on tryptic soy agar medium and incubate at 37℃ for 24h. Count the colonies, with 2 parallels for each group.

[0064] Then, the solutions of Comparative Example 1, Comparative Example 2 and Comparative Example 3 were used to conduct comparative experiments in the same manner as above, and the experimental results were as follows: Figure 3 shown.

[0065] from Figure 3It can be seen that the total number of Staphylococcus aureus in the blank control, Comparative Example 1 has a weak effect on Staphylococcus aureus and does not change with the change of illumination time. Comparative Examples 2 and 3 have an increased inhibitory effect on Staphylococcus aureus with the illumination time, and can completely eliminate Staphylococcus aureus at illumination times of 20min and 15min. The photosensitizer prepared by the optimal implementation method in Example 1 has a stronger and more excellent inhibitory effect on Staphylococcus aureus, and can completely eliminate Staphylococcus aureus in 5min, which has better antibacterial performance than Comparative Examples 1, 2 and 3.

[0066] Experimental Example 4:

[0067] First, activate the thermocidal Trichoderma and culture it at 25°C for 36 hours. Mix the photosensitizer prepared according to the best embodiment of Example 1 with the thermocidal Trichoderma liquid at a ratio of 2:1. The blank control is a mixture of 0.9% saline and thermocidal Trichoderma liquid at a ratio of 2:1. After incubation for 20 minutes, keep it in the dark or at 6 mW / cm 2 Irradiate with high-intensity 450nm visible light for 0-30min at a distance of 15cm. Spread 100μL of each sample after gradient dilution on tryptic soy agar medium and incubate at 25℃ for 24h. Count the colonies, with 2 parallels for each group.

[0068] Then, the solutions of Comparative Example 1, Comparative Example 2 and Comparative Example 3 were used to conduct comparative experiments in the same manner as above, and the experimental results were as follows: Figure 4 shown.

[0069] from Figure 4 It can be seen that the total number of thermophilic fungi in the blank control, comparative example 1 has almost no effect on thermophilic fungi and does not change with the change of illumination time. The inhibitory effect of comparative examples 2 and 3 on thermophilic fungi increases with the illumination time, and thermophilic fungi can be eliminated at an illumination time of 20 minutes. The photosensitizer prepared by the optimal implementation method in Example 1 has a stronger and more excellent inhibitory effect on thermophilic fungi, and thermophilic fungi can be completely eliminated in 10 minutes, which has better antibacterial performance than comparative examples 1, 2 and 3.

[0070] Experimental Example 5:

[0071] First, activate E. coli and culture it at 37°C for 36 hours. Take stainless steel, plastic, and glass, with the specific characteristics of 1 cm in length, 1 cm in width, and 0.1 cm in thickness. Take 2 mL of the activated bacterial solution and add it to a 24-well plate to soak the stainless steel sheet, plastic sheet, and glass sheet for 30 minutes respectively. Spray the soaked food contact surface with 0.9% saline and the photosensitizer prepared by the optimal implementation method in Example 1 respectively. After treatment, scrape the contact surface with a sterile cotton swab and shake it in 0.9% saline. Take 100 μL of saline containing the bacterial solution and spread it on the pancreatic casein soy peptone agar medium. Incubate at 37°C for 12 hours. When irradiating with LED visible light, the wavelength of the LED visible light is 450nm and the output power is 6mW / cm 2 The irradiation time was 20-30 min, the illumination distance was 15 cm, and the colony counts were performed, with 2 parallels in each group.

[0072] Then, a blank control group experiment was conducted, i.e., no photosensitizer was used for spraying, and the rest was the same as above. A dark control group experiment was conducted, i.e., photosensitizer was used for spraying, but no LED visible light was used. Each group had 2 parallels. The experimental results are shown in Figure 5 shown.

[0073] from Figure 5 It can be seen that the total number of E. coli on different contact surfaces treated with physiological saline, the photosensitizer prepared by the optimal implementation method in Example 1 has a strong inhibitory effect, and the E. coli remaining on the plastic sheet and glass sheet can be completely removed in 30 minutes, and the E. coli on the stainless steel sheet is less than 0.5Log CFU / mL, which has excellent ability to remove harmful bacteria in food.

[0074] Experimental Example 6:

[0075] First, activate Pseudomonas fragariae and culture it at 30°C for 36h. Take stainless steel, plastic, and glass, with the specific characteristics of 1cm in length, 1cm in width, and 0.1cm in thickness. Take 2mL of the activated bacterial solution and add it to a 24-well plate to soak the stainless steel sheet, plastic sheet, and glass sheet for 30min respectively. Spray the soaked food contact surface with 0.9% saline and the photosensitizer prepared in the best implementation method of Example 1. After treatment, scrape the contact surface with a sterile cotton swab and shake it in 0.9% saline. Take 100μL of saline containing the bacterial solution and spread it on the tryptic soy peptone agar medium. Incubate at 30°C for 24h, count the colonies, and do 2 parallels in each group.

[0076] Then, a blank control group experiment was conducted, i.e., no photosensitizer was used for spraying, and the rest was the same as above. A dark control group experiment was conducted, i.e., photosensitizer was used for spraying, but no LED visible light was used. Each group had 2 parallels. The experimental results are shown in Figure 6 shown.

[0077] from Figure 6 It can be seen that the total number of Pseudomonas fragariae on different contact surfaces treated with physiological saline, the photosensitizer prepared by the optimal implementation method in Example 1 has a strong inhibitory effect, and the residual Pseudomonas fragariae on stainless steel sheets, plastic sheets and glass sheets can be completely removed in 30 minutes, and it has excellent ability to remove harmful bacteria in food.

[0078] Experimental Example 7:

[0079] First, Staphylococcus aureus was activated and cultured at 37°C for 36h. Take stainless steel, plastic, and glass, with the specific characteristics of 1cm in length, 1cm in width, and 0.1cm in thickness. Take 2mL of the activated bacterial solution and add it to a 24-well plate to soak the stainless steel sheet, plastic sheet, and glass sheet for 30min respectively. The food contact surface after soaking was sprayed with 0.9% saline and the photosensitizer prepared by the best implementation method in Example 1. After treatment, the contact surface was scraped with a sterile cotton swab and shaken in 0.9% saline. Take 100μL of saline containing the bacterial solution and spread it on the tryptic soy bean agar medium, incubate at 37°C for 24h, and count the colonies, with 2 parallels in each group.

[0080] Then, a blank control group experiment was conducted, i.e., no photosensitizer was used for spraying, and the rest was the same as above. A dark control group experiment was conducted, i.e., photosensitizer was used for spraying, but no LED visible light was used. Each group had 2 parallels. The experimental results are shown in Figure 7 shown.

[0081] from Figure 7 It can be seen that the total number of Staphylococcus aureus on different contact surfaces treated with physiological saline, the photosensitizer prepared by the optimal implementation method in Example 1 has a strong inhibitory effect, and the Staphylococcus aureus remaining on the stainless steel sheet, plastic sheet and glass sheet can be completely removed in 20 minutes, and has excellent ability to remove harmful bacteria in food.

[0082] Experimental Example 8:

[0083] First, activate the heat-killed Trichoderma and culture it at 25°C for 36 hours. Take stainless steel, plastic, and glass, with the specific characteristics of 1 cm in length, 1 cm in width, and 0.1 cm in thickness. Take 2 mL of the activated bacterial solution and add it to a 24-well plate to soak the stainless steel sheet, plastic sheet, and glass sheet for 30 minutes respectively. Spray the soaked food contact surface with 0.9% saline and the photosensitizer prepared by the best implementation method in Example 1. After treatment, scrape the contact surface with a sterile cotton swab and shake it in 0.9% saline. Take 100 μL of saline containing the bacterial solution and spread it on the tryptic soy peptone agar medium. Incubate at 25°C for 24 hours, count the colonies, and do 2 parallels in each group.

[0084] Then, a blank control group experiment was conducted, i.e., no photosensitizer was used for spraying, and the rest was the same as above. A dark control group experiment was conducted, i.e., photosensitizer was used for spraying, but no LED visible light was used. Each group had 2 parallels. The experimental results are shown in Figure 8 shown.

[0085] from Figure 8 It can be seen that the total number of thermophilic fungi on different contact surfaces treated with physiological saline, the photosensitizer prepared by the optimal implementation method in Example 1 has a strong inhibitory effect, and the thermophilic fungi remaining on stainless steel sheets, plastic sheets and glass sheets can be completely removed in 20 minutes, and it has excellent ability to remove harmful bacteria in food.

[0086] In the present invention, the present invention adopts curcumin, octyl gallate and chitosan to prepare a novel photosensitizer, which improves the problems of poor water solubility and insufficient bactericidal effect of curcumin. Octyl gallate and curcumin can synergistically provide more efficient bactericidal effect, and chitosan can improve the water solubility and bactericidal effect of curcumin and octyl gallate. The inherent limitations of existing photosensitizers are solved.

[0087] Curcumin and chitosan are both safe food additives allowed for use in accordance with GBB2760-2021. Octyl gallate is a food additive for oils and lipid-rich foods approved for use by the U.S. Food and Drug Administration, the Food and Agriculture Organization of the United Nations, and the World Health Organization.

[0088] The new photosensitizer has a strong killing effect on Gram-negative bacteria and Gram-positive bacteria. As the illumination time increases, the bactericidal effect is significantly enhanced, and it has a stronger killing effect on Gram-positive bacteria. It can remove Gram bacteria that are difficult to remove on food contact surfaces to ensure food safety.

[0089] In general, the present invention is simple and convenient, has a short processing time, is low in cost, is green and pollution-free, is easy to be directly applied in the food industry, and has certain control and prevention effects, thus providing strong technical support for maintaining public health.

[0090] In the present invention, a novel photosensitizer is prepared by using curcumin, octyl gallate and chitosan as raw materials to improve the efficiency of PDI. The novel photosensitizer can have a broad-spectrum antibacterial property, be safe, non-toxic, and low-cost, and can effectively remove harmful bacteria on the food contact surface, thereby ensuring the safety of food processing.

[0091] The purpose of the present invention is to provide a method for preparing a novel photosensitizer prepared from curcumin, octyl gallate and chitosan as raw materials and a strategy for effective sterilization of food contact surfaces, so as to solve the existing problems of traditional technologies. The novel photosensitizer solves the problems of poor water solubility and insufficient bactericidal efficacy of curcumin, has excellent killing efficacy against both Gram-negative and Gram-positive bacteria, can greatly improve the bactericidal efficiency, and has broad-spectrum antibacterial properties.

[0092] The above is only a preferred embodiment of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principles of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. The structures, devices and operating methods not specifically described and explained in the present invention shall be implemented according to the conventional means in the art unless otherwise specified and limited.

Claims

1. A method for preparing an edible photosensitizer with high bactericidal performance, characterized in that: The following steps are involved: Step 1: Curcumin was dissolved in anhydrous ethanol to obtain a 1 mmol / L curcumin stock solution; octyl gallate was dissolved in anhydrous ethanol to obtain a 1 mmol / L octyl gallate stock solution; Step 2: adding chitosan to a 1% acetic acid solution to obtain a 0.5% chitosan solution; Step 3: taking a curcumin stock solution and a chitosan solution in a volume ratio of 0.5-2:20-30 parts and mixing them evenly to obtain a curcumin-chitosan solution; Step 4: Take 20-30 parts by volume of the curcumin-chitosan solution in a glass container, add 3-4 parts by volume of the octyl gallate stock solution and 4-5 parts by volume of the chitosan solution, and mix them to obtain an edible photosensitizer with high bactericidal performance.

2. The method for preparing a high bactericidal performance edible photosensitizer according to claim 1, characterized in that: The concentration of curcumin in the edible photosensitizer with high bactericidal performance is 12-70 μmol / L, and the concentration of octyl gallate is 75-150 μmol / L.

3. An application of an edible photosensitizer with high bactericidal performance in killing bacteria in food, characterized in that: The photosensitizer is a photosensitizer prepared by any one of the preparation methods in claims 1-2; the photosensitizer is sprayed on the surface of food, and then LED visible light is used for irradiation for a certain period of time to kill bacteria in the food.

4. The use of an edible photosensitizer with high bactericidal performance in killing bacteria in food according to claim 3, characterized in that: Bacteria in food that can be killed include: Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Thermomyces cerevisiae.

5. The use of an edible photosensitizer with high bactericidal performance in killing bacteria in food according to claim 3, characterized in that: When LED visible light is irradiated, the wavelength of LED visible light is 450nm and the output power is 6mW / cm 2 The irradiation time is 20-30min and the irradiation distance is 15cm.

6. Use of an edible photosensitizer with high bactericidal performance in photodynamic sterilization of food contact surfaces, characterized in that: The photosensitizer is a photosensitizer prepared by any one of the preparation methods of claims 1-2. The photosensitizer is sprayed on the food contact surface, and then irradiated with LED visible light for a certain period of time to kill the bacteria on the food contact surface.

7. The use of an edible photosensitizer with high bactericidal performance according to claim 6 in photodynamic sterilization of food contact surfaces, characterized in that: The food contact surface includes a stainless steel surface, a glass surface and a plastic surface.

8. The use of an edible photosensitizer with high bactericidal performance according to claim 6 in photodynamic sterilization of food contact surfaces, characterized in that: When LED visible light is irradiated, the wavelength of LED visible light is 450nm and the output power is 6mW / cm 2 The irradiation time is 20-30min and the irradiation distance is 15cm.

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