A method for sterilizing fresh-cut fruits by pulse ultraviolet irradiation combined with modified atmosphere packaging

Abstract

The application discloses a fresh-cut fruit sterilization method by pulse ultraviolet irradiation combined with modified atmosphere packaging. The method comprises the following steps: pulse ultraviolet irradiation of fresh-cut fruits for 60-90s, and then filling mixed gas for modified atmosphere packaging, wherein the mixed gas is composed of 4.7%-5.3% CO2 and 94.7%-95.3% N2 in volume fraction. The application sets air, 100% N2, 100% CO2 and 5% CO2+95% N2 modified atmosphere parameters, and pulse ultraviolet irradiation of fresh-cut fruits before and after packaging respectively. Through the combination of different gas characteristics and pulse ultraviolet irradiation, the removal and killing effect of microorganisms of fresh-cut fruits is enhanced. In the method, compared with air packaging, different modified atmosphere components such as 5% CO2+95% N2 have a significant sterilization effect on fresh-cut fruits, and improve the edible safety and actual production benefit of products.

Description

Technical Field

[0001] This invention belongs to the field of fresh-cut fruit preservation, specifically relating to a method for sterilizing fresh-cut fruit using pulsed ultraviolet irradiation combined with modified atmosphere packaging. Background Technology

[0002] With the increasing demand for convenient and healthy eating, fresh-cut fruits are widely favored by consumers due to their ready-to-eat nature and high nutrient retention. However, the physical cutting process during fresh-cut processing damages the fruit's tissue structure, causing cellular contents to leak out and leading to microbial contamination by spoilage bacteria, pathogens, and other microorganisms. This not only significantly shortens the shelf life of fresh-cut fruits, causing economic losses, but also poses a potential food safety risk.

[0003] Currently, ultraviolet (UV) irradiation is a mature non-thermal sterilization technology in the food industry, primarily achieving sterilization by disrupting the nucleic acid structure of microorganisms. However, traditional UV light suffers from drawbacks such as weak penetration. Pulsed light irradiation, as a novel non-thermal sterilization technology, utilizes a high-voltage power supply to release high-energy pulses within extremely short timeframes (microseconds to milliseconds), generating broad-spectrum, intense light in the UV, visible, and infrared bands. Sterilization is achieved through photochemical and photothermal effects, exhibiting high penetration, broad spectrum, and high efficiency. However, its action time is short and it lacks sustained antibacterial capabilities. Meanwhile, modified atmosphere packaging is a common physical method for extending the shelf life of fresh-cut fruits, inhibiting microbial metabolism by adjusting the gas composition (N2 and CO2, etc.) within the packaging. However, it is difficult to control initial microbial contamination of the product.

[0004] In summary, pulsed light and ultraviolet irradiation, as well as modified atmosphere packaging, are often used as independent technologies. There is a lack of systematic research on their synergistic effects, and a lack of processing methods for fresh-cut fruits that organically combine instantaneous and efficient sterilization with long-lasting and continuous antibacterial effects.

[0005] Therefore, there is an urgent need to develop a synergistic sterilization method that combines pulsed ultraviolet irradiation with modified atmosphere packaging, in order to provide theoretical basis and technical reference for the fresh-cut fruit and vegetable industry. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for sterilizing fresh-cut fruits using pulsed ultraviolet irradiation combined with modified atmosphere packaging.

[0007] The sterilization method for fresh-cut fruit provided by the present invention includes the following steps: the fresh-cut fruit is first irradiated with pulsed ultraviolet light for 60 to 90 seconds, and then filled with a mixed gas for modified atmosphere packaging, wherein the mixed gas is composed of CO2 with a volume fraction of 4.7% to 5.3% and N2 with a volume fraction of 94.7% to 95.3%.

[0008] In a specific embodiment of the present invention, the mixed gas consists of 5.0% CO2 and 95.0% N2 by volume.

[0009] In some embodiments of the present invention, the fruit is a berry.

[0010] In a specific embodiment of the present invention, the berry fruit is fresh-cut orange or kiwi.

[0011] In some embodiments of the present invention, the modified atmosphere packaging involves placing fresh-cut fruit irradiated with pulsed ultraviolet light into a modified atmosphere packaging box or bag for modified atmosphere packaging.

[0012] In some embodiments of the present invention, the pressure of the mixed gas inside the modified atmosphere packaging box or modified atmosphere packaging bag is 0.1 ~ 0.5 MPa.

[0013] In some embodiments of the present invention, the parameters of the modified atmosphere packaging machine used for the modified atmosphere packaging are set as follows: vacuuming time 3.95 ~ 4.05 s, inflation time 0.60 ~ 1.00 s, heat sealing mold temperature 139℃ ~ 141℃, sealing time 1.45 ~ 1.55 s, and deflation time 0.95 ~ 1.05 s.

[0014] In a specific embodiment of the present invention, the parameters of the modified atmosphere packaging machine used for the modified atmosphere packaging are set as follows: vacuuming time 4 s, inflation time 0.60 ~ 1.00 s, heat sealing mold temperature 140℃, sealing time 1.5 s, and degassing time 1 s.

[0015] In some embodiments of the present invention, the pulsed ultraviolet irradiation is achieved by simultaneously using three types of lamps: ultraviolet lamps, magnetic energy lamps, and pulse lamps, thus realizing combined ultraviolet (ultraviolet lamps and magnetic energy lamps) and pulse (pulse lamp) irradiation. The ultraviolet irradiation intensity parameters of the lamps used are: ultraviolet lamp 145 μw / cm². 2 Magnetic energy lamp 700 μw / cm 2 10600 μw / cm UV lamp 2 If converted to irradiation energy, it needs to be multiplied by the corresponding actual irradiation time for conversion, i.e., irradiation energy (J / cm²). 2 = Irradiation intensity (μw / cm) 2 ) × Irradiation time (s) × 10 -6 .

[0016] In some embodiments of the present invention, the irradiation dose of the pulsed ultraviolet irradiation is 0.34 ~ 1.03 J / cm².

[0017] In a specific embodiment of the present invention, the irradiation dose of the pulsed ultraviolet irradiation is 0.69 ~ 1.03 J / cm².

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention employs four gas filling ratios: air, 100% N2, 100% CO2, and 5% CO2 + 95% N2. Fresh-cut fruits are sequentially subjected to modified atmosphere packaging (MAP) followed by pulsed ultraviolet irradiation, resulting in varying degrees of reduction in total bacterial count and total mold and yeast count. The optimal conditions are 60-90 seconds of pulsed ultraviolet irradiation followed by filling with 5% CO2 + 95% N2 for MAP. This method is applicable to various fresh-cut fruit systems, producing significant sterilization effects and improving product safety and actual production efficiency. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0020] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0021] In the following implementation, pulsed ultraviolet irradiation is achieved by simultaneously using three types of lamps: ultraviolet lamps, magnetic energy lamps, and pulse lamps, thus combining ultraviolet (ultraviolet lamps and magnetic energy lamps) and pulsed (pulse lamp) irradiation. The ultraviolet irradiation intensity parameters of the lamps used are: ultraviolet lamp 145 μw / cm². 2 Magnetic energy lamp 700 μw / cm 2 10600 μw / cm UV lamp 2 .

[0022] Example 1 1. This experiment used a transparent PP packaging box with dimensions of 22*13*4 cm (length*width*height). The internal pressure of the box after packaging was 0.1~0.5 MPa. The modified atmosphere packaging machine was preheated for 10 min. The heat sealing mold temperature was set to 140℃, the sealing time to 1.5 s, and the venting time to 1 s. Different gas compositions (air, 100% N2, 100% CO2, 5% CO2 + 95% N2) and their vacuum and top and bottom inflation times were adjusted (Table 1). 2. Four untreated fresh-cut fruits (oranges / kiwis) were first (or second) packaged with modified atmosphere packaging, and then (first) subjected to pulsed ultraviolet irradiation for different times (30, 60, 90 s) as the experimental group; 3. Four untreated fresh-cut fruits (oranges / kiwis) were filled with different gas compositions (air, 100% N2, 100% CO2, 5% CO2 + 95% N2) for modified atmosphere packaging, serving as a control group; 4. Transfer the packaged fresh-cut fruit (orange / kiwi) to an Erlenmeyer flask containing 225 mL of sterile water. After shaking for 5 min, the first gradient sample dilution was obtained. The total bacterial count and mold and yeast count were determined according to GB 4789.2—2022 and GB 4789.15—2016. The results are shown in Tables 2 and 3.

[0023] Table 1 Modified Atmosphere Packaging Parameters

[0024] As shown in Table 2, compared with the unirradiated group, the total bacterial count and mold / yeast count of the irradiated fresh-cut oranges were significantly reduced, indicating that pulsed ultraviolet irradiation has a sterilization effect on fresh-cut oranges. With increasing irradiation time, the number of microorganisms showed a decreasing trend. When the irradiation time was 90 s, the total bacterial count and mold / yeast count decreased by 0.60 lg CFU / g and 0.76 lg CFU / g, respectively. Comparison of different modified atmosphere packaging compositions revealed that 100% N2, 100% CO2, and 5% CO2 + 95% N2 packaging showed better sterilization effects than air, especially the 5% CO2 + 95% N2 packaging. This may be because N2 acts as a good light-penetrating medium, while 5% CO2 inhibits microbial metabolism and produces a synergistic effect with pulsed ultraviolet irradiation sterilization. Furthermore, in terms of overall bacterial reduction, irradiation before packaging resulted in a better removal of the total bacterial count than packaging before irradiation. In summary, the optimal conditions for fresh-cut oranges are modified atmosphere packaging with 5% CO2 + 95% N2 after 90 seconds of pulsed ultraviolet irradiation.

[0025] Note: The above reduction values ​​of total colony count or mold and yeast count are obtained by subtracting the number of unirradiated groups and experimental groups, i.e.: reduction value = unirradiated group - experimental group. For example: reduction value of mold and yeast (0.76) = unirradiated (2.08) - experimental group (1.32). The same applies to the total colony count.

[0026] Table 2. Effects of modified atmosphere packaging combined with pulsed ultraviolet irradiation on the number of microorganisms in fresh-cut oranges.

[0027] Note: Different lowercase letters indicate significant differences between different irradiation times. p <0.05).

[0028] As shown in Table 3, compared with the unirradiated group, the total bacterial count and total mold and yeast count of fresh-cut kiwifruit were significantly reduced after irradiation, indicating that pulsed ultraviolet irradiation has a sterilization effect on fresh-cut kiwifruit. With increasing irradiation time, the number of microorganisms decreased. After 60 seconds of irradiation, both the total bacterial count and the total mold and yeast count reached or approached their minimum values. Specifically, the total bacterial count decreased by 1.26 lg CFU / g, and the total mold and yeast count decreased by 0.92 lg CFU / g. Furthermore, different gas components in modified atmosphere packaging can affect the final sterilization effect. In terms of total bacterial count, 5% CO2 + 95% N2 packaging showed the best sterilization effect, and irradiation followed by packaging was significantly better than packaging first. Therefore, the optimal conditions for modified atmosphere packaging of fresh-cut kiwifruit are 60 seconds of pulsed ultraviolet irradiation followed by 5% CO2 + 95% N2.

[0029] Table 3. Effects of modified atmosphere packaging combined with pulsed ultraviolet irradiation on the microbial abundance of fresh-cut kiwifruit.

[0030] Note: Different lowercase letters indicate significant differences between different irradiation times. p <0.05).

[0031] In summary, modified atmosphere packaging combined with pulsed ultraviolet irradiation has a sterilization effect on fresh-cut fruits, and the sterilization effect varies under different modified atmosphere components, packaging order, and irradiation time. Specifically, the optimal conditions for fresh-cut oranges and kiwis are modified atmosphere packaging with 5% CO2 + 95% N2 after 60-90 seconds of pulsed ultraviolet irradiation.

[0032] The present invention has been described in detail above. For those skilled in the art, the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. Although specific embodiments have been given, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein. Some of the essential features can be applied within the scope of the following appended claims.

Claims

1. A method for sterilizing fresh-cut fruit, comprising the following steps: first, irradiating the fresh-cut fruit with pulsed ultraviolet light for 60-90 seconds, then filling it with a mixed gas for modified atmosphere packaging, wherein... The mixed gas consists of 4.7% to 5.3% CO2 by volume and 94.7% to 95.3% N2 by volume.

2. The method according to claim 1, characterized in that: The fruit in question is a type of berry.

3. The method according to claim 2, characterized in that: The berry-type fruits are oranges or kiwis.

4. The method according to any one of claims 1-3, characterized in that: Modified atmosphere packaging involves placing fresh-cut fruit that has been irradiated with pulsed ultraviolet light into a modified atmosphere packaging box or bag for modified atmosphere packaging.

5. The method according to claim 4, characterized in that: The pressure of the mixed gas inside the modified atmosphere packaging box or bag is 0.1 ~ 0.5 MPa.

6. The method according to any one of claims 1-5, characterized in that: The parameters of the modified atmosphere packaging machine used for the modified atmosphere packaging are set as follows: vacuuming time 3.95 ~ 4.05 s, inflation time 0.60 ~ 1.00 s, heat sealing mold temperature 139℃ ~ 141℃, sealing time 1.45 ~ 1.55 s, and degassing time 0.95 ~ 1.05 s.

7. The method according to any one of claims 1-6, characterized in that: The irradiation dose of the pulsed ultraviolet irradiation is 0.34 ~ 1.03 J / cm².

8. The method according to any one of claims 1-7, characterized in that: The method can significantly reduce the total bacterial count and mold and yeast count of the fresh-cut fruit.

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