Method for illumination control of preservation of papaya fruit and application thereof

Abstract

This invention discloses a light control method for preserving papaya fruit and its application. The light control method involves irradiating the papaya fruit with blue light, and its application in papaya fruit preservation is also disclosed. This invention successfully solves the problem of the short shelf life of papaya fruit at room temperature. By utilizing LED blue light irradiation technology, it significantly extends the shelf life of papaya fruit at room temperature, effectively delays ripening and softening, maintains fruit quality, and effectively reduces post-harvest losses. This provides a green and safe new method for extending the shelf life of papaya fruit.

Description

Technical Field

[0001] This invention relates to the field of fruit preservation, specifically to a method for controlling light intensity in the preservation of papaya fruit and its application. Background Technology

[0002] Light-emitting diode (LED) irradiation technology uses artificial light to supplement illumination or provide plants with specific light secondary to regulate their growth and development. Compared with traditional light sources, LEDs are energy-efficient, durable, have a long lifespan, are low-cost, and generate little heat. Existing technologies utilize different types of LED light, including ultraviolet, blue, red, and far-red light, to provide pre-harvest supplemental lighting for fruits, thereby improving the nutritional content and quality of fruits and vegetables.

[0003] The diverse and vibrant colors of fruits and vegetables are an important attribute for assessing their value. These colors originate from pigments, and light is a major factor influencing pigment accumulation. Current technologies utilize LED light of different colors to treat fruits and vegetables, effectively maintaining and increasing the content of pigments such as chlorophyll, epidermal pigments, carotenoids, and anthocyanins. Furthermore, the nutrients in fruits provide essential nutrition and energy for the human body. LED irradiation can effectively maintain the post-harvest nutritional quality of fruits, increase soluble solids content, effectively slow down the rate of sugar content decline during later storage, and effectively maintain the sugar content of fruits.

[0004] Papaya (Carica papaya L.) originated in tropical America and is mainly cultivated in tropical and subtropical regions of my country, such as Guangdong, Hainan, and Taiwan. Its flesh is delicious and sweet, rich in vitamin C, minerals, and other nutrients, making it extremely nutritious and earning it the nickname "fruit of longevity." Papaya is a climacteric fruit, sensitive to ethylene during storage and distribution, and undergoes a significant physiological ripening process. It ripens and softens rapidly after harvest and is highly sensitive to biotic and abiotic stresses, easily softening and rotting. Papaya is primarily sold fresh; improper preservation at room temperature after harvest can lead to severe fruit rot and losses during storage and sales. Current technologies often employ low-temperature and modified atmosphere packaging to extend the shelf life of papaya, but these methods can easily cause chilling injury or off-flavors. Simple, effective, low-carbon, and environmentally friendly papaya preservation methods are scarce. Therefore, effective, low-carbon, and environmentally friendly room-temperature preservation methods are crucial for the development of the papaya industry. Summary of the Invention

[0005] To address the difficulties in preserving papaya at room temperature and the lack of effective room temperature preservation technologies in existing technologies, this invention provides a light control method for preserving papaya fruit and its application.

[0006] The first objective of this invention is to provide a method for controlling light exposure to preserve papaya fruit.

[0007] The second objective of this invention is to provide a method for preserving papaya fruit.

[0008] To achieve the above objectives, the present invention is implemented through the following solution:

[0009] The main purpose of storing papaya fruit is to delay its ripening and senescence, and to maintain its flavor, texture, and other characteristics during storage. This invention is the first to discover that treating papaya fruit with LED blue light can effectively inhibit fruit respiration, enhance the fruit's antioxidant capacity, reduce oxygen damage, thereby delaying ripening and extending its storage and shelf life at room temperature.

[0010] A method for controlling light exposure to preserve papaya fruit involves irradiating the papaya fruit with blue light.

[0011] Preferably, the light-emitting device containing the blue light is a light-emitting diode, i.e., an LED.

[0012] More preferably, the wavelength of the blue light is 430nm to 470nm.

[0013] Preferably, the intensity of the blue light is 48 Lux to 52 Lux.

[0014] More preferably, the intensity of the blue light is 49.5 Lux.

[0015] More preferably, the papaya fruit is irradiated with blue light from a light-emitting diode, wherein the wavelength of the blue light is 430nm to 470nm and the light intensity is 48Lux to 52Lux.

[0016] Most preferably, the papaya fruit is irradiated with blue light from a light-emitting diode, wherein the wavelength of the blue light is 430nm to 470nm and the light intensity is 49.5Lux.

[0017] Preferably, the papaya fruit is immature before irradiation; the criteria for determining that the papaya fruit is immature are as follows: the peel color is 5% to 15% yellow according to the national standard "NY / T 691-2018 Papaya".

[0018] More preferably, before irradiation, the color of the papaya fruit peel is measured to be 5% yellow according to the national standard "NY / T 691-2018 Papaya".

[0019] Preferably, during the irradiation process, there are no other light sources besides the blue light.

[0020] The application of any of the above-mentioned light control methods in the preservation of papaya fruit should also be within the scope of protection of this invention.

[0021] A method for preserving papaya fruit, wherein individually packaged papaya fruit is treated in a dark environment using any of the above-described light control methods.

[0022] Preferably, the light-emitting device containing the blue light is a light-emitting diode, i.e., an LED.

[0023] More preferably, the wavelength of the blue light is 430nm to 470nm.

[0024] Preferably, the intensity of the blue light is 48 Lux to 52 Lux.

[0025] More preferably, the intensity of the blue light is 49.5 Lux.

[0026] More preferably, the papaya fruit is irradiated with blue light from a light-emitting diode, wherein the wavelength of the blue light is 430nm to 470nm and the light intensity is 48Lux to 52Lux.

[0027] Most preferably, the papaya fruit is irradiated with blue light from a light-emitting diode, wherein the wavelength of the blue light is 430nm to 470nm and the light intensity is 49.5Lux.

[0028] Preferably, the temperature of the dark environment is 25°C.

[0029] Preferably, the humidity of the dark environment is 60% RH to 80% RH.

[0030] More preferably, the temperature of the dark environment is 25°C and the humidity is 60% RH to 80% RH.

[0031] More preferably, the temperature of the dark environment is 24°C to 26°C and the humidity is 70% RH.

[0032] More preferably, the temperature of the dark environment is 25°C and the humidity is 70%rh.

[0033] Preferably, the papaya fruit is unripe before processing; the criteria for determining that the papaya fruit is unripe are as follows: the peel color is 5% to 15% yellow according to the national standard "NY / T 691-2018 Papaya".

[0034] More preferably, before treatment, the papaya fruit peel color is measured to be 5% yellow according to the national standard "NY / T 691-2018 Papaya".

[0035] Preferably, no other light source is used during the processing except for the blue light.

[0036] Preferably, the papaya fruit is washed and disinfected before processing.

[0037] More preferably, the disinfection method is as follows: soak the fresh cut of the fruit stalk in 0.1% (w / v) to 0.3% (w / v) "strong" (chlorine dioxide) bactericide, then soak it in a mixture of urea and imazalil, and then air dry.

[0038] More preferably, the soaking time of the "powerful" (chlorine dioxide) bactericide is 8 min to 12 min.

[0039] More preferably, the soaking time of the "powerful" (chlorine dioxide) bactericide is 10 minutes.

[0040] More preferably, the mixture of thiamethoxam and imazalil is obtained by thoroughly mixing thiamethoxam and imazalil at a mass ratio of 1:(1-2).

[0041] More preferably, the mixture of thiamethoxam and imazalil is obtained by thoroughly mixing thiamethoxam and imazalil at a mass ratio of 1:1.

[0042] More preferably, the soaking time of the mixture of tebuconazole and imazalil is 1 min to 2 min.

[0043] More preferably, the soaking time of the mixture of tebuconazole and imazalil is 1 minute.

[0044] Preferably, the papaya fruits are individually packaged before processing.

[0045] More preferably, individual fruits are packaged using plastic film.

[0046] More preferably, the plastic film is a polyethylene film.

[0047] More preferably, the polyethylene film is an open polyethylene film bag.

[0048] More preferably, the thickness of the polyethylene film is 0.01 mm to 0.02 mm.

[0049] More preferably, the thickness of the polyethylene film is 0.02 mm.

[0050] Specifically, the method for preserving papaya fruit includes the following steps:

[0051] S1. According to the national standard "NY / T 691-2018 Papaya", determine the degree of yellowing of the papaya fruit peel; select papaya fruits with a peel color showing 5% yellowing, uniform size, consistent maturity and no mechanical damage, and harvest them with a 2cm to 3cm fruit stalk.

[0052] S2. After washing away the dust on the surface of the fruit with clean water and drying it, make a new wound at the stem. Soak the whole fruit in a 0.2% (w / v) "strong" (chlorine dioxide) fungicide for 10 minutes, then soak the whole fruit in a 1:1 mixture of urea and imazalil for 1 minute, and then take it out and dry it.

[0053] S3. The papaya fruits obtained in the previous step are bagged and kept moist. Each papaya fruit is individually packaged in a 0.02mm thick polyethylene film bag without sealing. The fruit is stored in a dark, lightless room and continuously irradiated with LED blue light of wavelength 430nm~470nm at an intensity of 49.5Lux until the end of storage. The temperature during storage is 25℃ and the humidity is 70%rh.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] Existing technologies using LED light to treat climacteric fruits primarily promote fruit ripening but fail to achieve the goal of preserving papaya fruit. This invention successfully solves the problem of the short shelf life of papaya fruit at room temperature. By utilizing LED blue light irradiation technology, it significantly extends the shelf life of papaya fruit at room temperature, effectively delaying ripening and softening, maintaining fruit quality, and significantly reducing post-harvest losses. This provides a green and safe new method for extending the shelf life of papaya fruit. Attached Figure Description

[0056] Figure 1 A shows the yellowing of papaya fruits under different treatments; A is a photograph of papaya fruits under different treatments; B is the result of the yellowing index measurement. Different letters represent significant differences in the t-test (P<0.05).

[0057] Figure 2 The results of colorimetric measurements of papaya fruits under different treatments are shown in Figure 1. A represents the measurement results of brightness; B represents the measurement results of color saturation; C represents the measurement results of color angle; different letters represent significant differences in t-tests (P<0.05).

[0058] Figure 3 The results show the firmness of papaya fruits treated with different methods; different letters represent significant differences in t-test (P<0.05).

[0059] Figure 4 The results of respiration rate measurements of papaya fruits under different treatments; different letters represent significant differences in t-tests (P<0.05).

[0060] Figure 5 The results of malondialdehyde (MDA) content determination in papaya fruits under different treatments; different letters represent significant differences in t-detection (P<0.05).

[0061] Figure 6 The results of superoxide dismutase activity assays in papaya fruits treated with different methods are shown; different letters represent significant differences in t-detection (P<0.05).

[0062] Figure 7 Results of flavonoid content determination in papaya fruits under different treatments; different letters represent significant differences in t-detection (P<0.05).

[0063] Figure 8 The results show the total phenolic content of papaya fruits under different treatments; different letters represent significant differences in t-detection (P<0.05).

[0064] Figure 9 The results of reducing ascorbic acid content determination in papaya fruits under different treatments; different letters represent significant differences in t-detection (P<0.05).

[0065] Figure 10 The results of chitinase activity assays in papaya fruits treated with different methods are shown; different letters represent significant differences in t-detection (P<0.05).

[0066] Figure 11 Results of polygalacturonase activity assay in papaya fruits treated with different methods; different letters represent significant differences in t-test (P<0.05).

[0067] Figure 12 The results of pectin lyase activity assays in papaya fruits treated with different methods are shown; different letters represent significant differences in t-tests (P<0.05).

[0068] Figure 13 Photographs of banana fruits treated with different methods.

[0069] Figure 14 The results of colorimetry measurements on banana fruits under different treatments are shown in Figure 1. A represents the measurement results of brightness; B represents the measurement results of color saturation; C represents the measurement results of chromaticity angle; * indicates a significant difference in t-test (P<0.05), and ** indicates a highly significant difference in t-test (P<0.01).

[0070] Figure 15 The results of firmness determination of banana fruits under different treatments; * indicates a significant difference in t-test (P<0.05), ** indicates a highly significant difference in t-test (P<0.01).

[0071] Figure 16 Photographs of banana fruits treated with different methods.

[0072] Figure 17 The results of colorimetric measurements of banana fruits under different treatments are shown in Figure 1. A represents the measurement results of brightness; B represents the measurement results of color saturation; C represents the measurement results of chromaticity angle; different letters represent significant differences in t-tests (P<0.05).

[0073] Figure 18 The results of firmness determination of banana fruits under different treatments; different letters represent significant differences in t-test (P<0.05).

[0074] Figure 19 The results show the respiration rate of banana fruits under different treatments; different letters represent significant differences in t-tests (P<0.05). Detailed Implementation

[0075] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available.

[0076] Example 1: A method for preserving papaya fruit

[0077] 1. Picking

[0078] According to the national standard "NY / T 691-2018 Papaya", determine the degree of yellowing of the papaya fruit peel.

[0079] Select papaya fruits with a peel color showing 5% yellowing, uniform size, consistent maturity, and no mechanical damage, and harvest them with a 2cm-3cm stem attached.

[0080] 2. Cleaning and disinfection

[0081] Wash away the dust on the surface of the papaya fruit with clean water, let it air dry naturally, select fruits that are similar in size, free from disease and mechanical damage, and make new wounds at the fruit stem.

[0082] Soak the whole fruit in a 0.2% (w / v) "Strong" (chlorine dioxide) fungicide solution for 10 minutes, then soak the whole fruit in a 1:1 mixture of urea ("Fresh Fruit Star", purchased from Jiangsu Kuida Agrochemical Co., Ltd.) and imazalil ("Baike", purchased from Jiangsu Huifeng Bio-Agriculture Co., Ltd.) for 1 minute, then remove and air dry.

[0083] 3. Light control

[0084] The papaya fruits obtained in the previous step were bagged and kept moist. Each papaya fruit was individually packaged in a 0.02mm thick polyethylene film bag without sealing. The fruit was stored in a dark, lightless room and continuously irradiated with LED blue light with a wavelength of 430nm to 470nm and an intensity of 49.5Lux until the end of storage. The storage temperature was 25℃ and the humidity was 70%rh.

[0085] Example 2: A method for preserving papaya fruit

[0086] 1. Picking

[0087] According to the national standard "NY / T 691-2018 Papaya", determine the degree of yellowing of the papaya fruit peel.

[0088] Select papaya fruits with 10% yellowing peel, uniform size, consistent maturity, and no mechanical damage, and harvest them with a 2cm-3cm stem attached.

[0089] 2. Cleaning and disinfection

[0090] Wash the papaya fruit with clean water to remove the dust from its surface. After drying, select fruits that are similar in size, free from disease and mechanical damage, and make new cuts at the stem end.

[0091] Soak the whole fruit in a 0.3% (w / v) "Strong" (chlorine dioxide) fungicide solution for 8 minutes, then soak the whole fruit in a 1:1 mixture of urea ("Fresh Fruit Star", purchased from Jiangsu Kuida Agrochemical Co., Ltd.) and imazalil ("Baike", purchased from Jiangsu Huifeng Bio-Agriculture Co., Ltd.) for 1 minute, then remove and air dry.

[0092] 3. Light control

[0093] The papaya fruits obtained in the previous step were bagged and kept moist. The papaya fruits were individually packaged in unsealed polyethylene film bags with a thickness of 0.01 mm and stored in a dark, lightless room. They were continuously irradiated with LED blue light with a wavelength of 430 nm to 470 nm and an intensity of 48 Lux until the end of storage. The temperature during storage was 26 °C and the humidity was 60% RH.

[0094] Example 3: A method for preserving papaya fruit

[0095] 1. Picking

[0096] According to the national standard "NY / T 691-2018 Papaya", determine the degree of yellowing of the papaya fruit peel.

[0097] Select papaya fruits with 15% yellow peel color, uniform size, consistent maturity, and no mechanical damage, and harvest them with a 2cm-3cm stem.

[0098] 2. Cleaning and disinfection

[0099] Wash the papaya fruit with clean water to remove the dust from its surface. After drying, select fruits that are similar in size, free from disease and mechanical damage, and make new cuts at the stem end.

[0100] Soak the whole fruit in a 0.1% (w / v) "Strong" (chlorine dioxide) fungicide solution for 12 minutes, then soak the whole fruit in a 1:1 mixture of urea ("Fresh Fruit Star", purchased from Jiangsu Kuida Agrochemical Co., Ltd.) and imazalil ("Baike", purchased from Jiangsu Huifeng Bio-Agriculture Co., Ltd.) for 1 minute, and then remove and air dry.

[0101] 3. Light control

[0102] The papaya fruits obtained in the previous step were bagged and kept moist. Each papaya fruit was individually packaged in a 0.02mm thick polyethylene film bag without sealing. The papaya fruits were stored in a dark, lightless room and continuously irradiated with LED blue light with a wavelength of 430nm to 470nm and an intensity of 52Lux until the end of storage. The temperature during storage was 24℃ and the humidity was 80%rh.

[0103] Comparative Example 1: A method for processing papaya fruit

[0104] The method is basically the same as in Example 1, except that in step 3, "light control", the papaya fruits are individually packaged in unsealed polyethylene film bags with a thickness of 0.02 mm and stored in a dark, lightless room without any light treatment.

[0105] Comparative Example 2: A method for processing papaya fruit

[0106] The method is basically the same as in Example 1, except that in step 3, “light control”, the papaya fruits are individually packaged in unsealed polyethylene film bags with a thickness of 0.02 mm and stored in a dark, lightless room. They are continuously irradiated with white LED light at an intensity of 49.5 Lux until the end of storage. The temperature during storage is 25°C and the humidity is 70% RH.

[0107] Application Example 1: The Preservation Effect of Different Treatment Methods on Papaya Fruit

[0108] 1. Experimental Methods

[0109] The papaya of the Dabai variety was used as the experimental subject. The papayas were harvested, cleaned and disinfected according to the methods of Examples 1-3 and Comparative Examples 1-2. They were then randomly divided into 5 groups with 3 replicates in each group. The papayas were then treated and stored according to the methods of Examples 1-3 and Comparative Examples 1-2 for a total of 10 days. The papayas treated by different methods were photographed periodically.

[0110] Physiological indicators of papaya fruit were measured every two days, including yellowing index grading, color, firmness, respiration rate, malondialdehyde content, superoxide dismutase activity, flavonoid content, total phenol content, reduced ascorbic acid content, chitinase activity, polygalacturonase activity, and pectin lyase activity.

[0111] (1) Assessment of Yellowing Index

[0112] Referring to existing techniques (DOI:10.1371 / journal.pone.0044405), the yellowing level of papaya fruits was assessed according to the following criteria:

[0113] Grade 1 is characterized by: green fruit color, with a slight yellow stripe appearing on the yellow peel, accounting for 0% to 15% of the peel surface;

[0114] Grade 2 is characterized by 2-3 yellow lines on the fruit surface to 1 / 4 of the fruit surface turning yellow (accounting for 15%-25% of the fruit peel surface area);

[0115] Grade 3 is defined as: 1 / 4 of the fruit surface turning yellow to 1 / 2 of the fruit surface turning yellow;

[0116] Grade 4 is characterized by: distinct yellow lines, green fading between the two yellow lines, and yellow covering more than green on the fruit surface (accounting for 50% to 80% of the peel);

[0117] Level 5 is defined as: three or more green lines turning yellow, and most of the fruit surface turning yellow (4 / 5 turning yellow, accounting for 80% of the peel);

[0118] Level 6 is defined as: the entire fruit surface turns from yellow to orange-yellow (accounting for 100% of the fruit peel surface area).

[0119] According to the calculation formula: The yellowing index of papaya fruits in each group was calculated.

[0120] (2) Determination of fruit color

[0121] Referring to the existing technology (DOI:10.1371 / journal.pone.0044405), a Minolta CR300 colorimeter from Konica Minolta Corporation was used to measure the brightness, color saturation, and chromaticity angle values ​​at five points evenly selected along the equator at the center of the fruit, and the average value was taken.

[0122] (3) Determination of fruit firmness

[0123] Five points were evenly selected along the equator at the center of the fruit. The skin was gently peeled off with a blade, and the flesh was tested using an Edberg GY-4 digital fruit firmness tester (probe diameter 8mm) to determine the fruit firmness.

[0124] (4) Measurement of fruit respiration rate

[0125] Referring to existing techniques (Wang Yi, Tian Shiping, Xu Yong, et al. Effects of silica window bag treatment on respiration rate and ethylene release rate of Feicheng peach fruit [J]. Journal of Horticulture, 2000(05):331-334.), three fruits from each group were placed in a sealed jar. After sealing for 2 hours, the jar was gently shaken (without damaging the fruit) to mix the gas evenly. Then, 1 mL of gas was extracted from the jar using a syringe, and the CO2 content in the gas was determined using a Hitachi G3900 gas chromatograph (6 parallel determinations). According to the formula: The respiration rate of the fruit was calculated.

[0126] (5) Determination of malondialdehyde content

[0127] The malondialdehyde (MDA) content in the pulp was determined using a malondialdehyde microplate assay kit (Suzhou Greens Biotechnology Co., Ltd.).

[0128] Malondialdehyde condenses with thiobarbituric acid to form a red product with a maximum absorption peak at 532 nm. Measuring the absorbance at this wavelength can estimate the content of lipid peroxides in the sample. Simultaneously, the absorbance at 600 nm is measured, and the content of malondialdehyde is calculated using the difference between the absorbance at 532 nm and 600 nm.

[0129] (6) Determination of superoxide dismutase activity

[0130] Superoxide dismutase (SOD) activity in fruit pulp was determined using a micro-method kit (WST-8 method) (Suzhou Grease Biotechnology Co., Ltd.). The kit works by generating superoxide anions through a xanthine and xanthine oxidase reaction system. These superoxide anions react with WST-8 to produce the water-soluble dye formazan, which absorbs at 450 nm. SOD scavenges superoxide anions, thus inhibiting formazan formation.

[0131] (7) Determination of flavonoid content

[0132] The flavonoid content in fruit pulp was determined using a plant flavonoid micro-method kit (Suzhou Grees Biotechnology Co., Ltd.). The kit works by reacting flavonoids with aluminum ions in an alkaline nitrite solution to form a red complex with a characteristic absorption peak at 510 nm. By measuring the absorbance of the sample extract at 510 nm, the flavonoid content of the sample can be calculated.

[0133] (8) Determination of total phenol content

[0134] The total phenol content in fruit pulp was determined using a total phenol micro-method kit (Suzhou Greens Biotechnology Co., Ltd.). The kit works on the principle that under alkaline conditions, phenolic substances reduce tungsticotropic acid to produce a blue compound with a characteristic absorption peak at 760 nm. Measuring the absorbance at 760 nm yields the total phenol content of the sample.

[0135] (9) Determination of reduced ascorbic acid content

[0136] The content of reduced ascorbic acid in fruit pulp was determined using a micro-ascorbic acid assay kit (Suzhou Greens Biotechnology Co., Ltd.). The detection principle of this kit is as follows: in acetic acid solution, ascorbic acid reacts with Solid Blue Salt B to generate a yellow oxalohydrazide-2-hydroxybutyryl lactone derivative, and the absorbance is measured at the maximum absorption wavelength of 420 nm.

[0137] (10) Determination of chitinase activity

[0138] The activity of chitinase in fruit pulp was determined using a chitinase micro-method kit (Suzhou Grees Biotechnology Co., Ltd.). The kit works by the following principle: chitinase hydrolyzes chitin to produce N-acetylglucosamine, which reacts with DNS reagent to form a brownish-red compound with a characteristic absorption peak at 540 nm. The enzyme activity is calculated by measuring the absorbance at 540 nm.

[0139] (11) Determination of polygalacturonase activity

[0140] The polygalacturonase activity in fruit pulp was determined using a micro-method kit for polygalacturonase activity (Suzhou Grease Biotechnology Co., Ltd.). The kit works by hydrolyzing pectinic acid to produce galacturonic acid, which has a reducing aldehyde group. This galacturonic acid reacts with DNS reagent to form a reddish-brown substance with a characteristic absorption peak at 540 nm. The polygalacturonase activity is calculated by measuring the change in absorbance at 540 nm.

[0141] (12) Determination of pectin lyase activity

[0142] The pectin lyase micro-method kit (Suzhou Greens Biotechnology Co., Ltd.) was used to determine the pectin lyase activity in fruit pulp. The kit works by using pectin lyase to act on the α-1,4 glycosidic bonds in pectin to generate unsaturated oligogalacturonic acid, which has a characteristic absorption peak at 235 nm. By measuring the absorbance at 235 nm, the pectin lyase activity of the sample can be calculated.

[0143] 2. Experimental Results

[0144] (1) Results of the yellowing index measurement

[0145] like Figure 1As shown in Figure A, the papaya fruits treated with Comparative Example 1 (CK) and Comparative Example 2 (LED white light) began to change color on the second day of storage, turning significantly yellow by the sixth day. Furthermore, the papaya fruits treated with Comparative Example 1 (CK) showed severe spoilage by the tenth day of storage (photos not shown, and physiological indicators were not measured). In contrast, the papaya fruits treated with Example 1 (LED blue light) remained green on the eighth day of storage. The papaya fruits treated with Examples 2 and 3 showed similar results to those of Example 1.

[0146] like Figure 1 As shown in Figure B, from the second day of storage, the yellowing index of papaya fruits treated with Example 1 (i.e., LED blue light) was lower than that of papaya fruits treated with Comparative Example 1 (i.e., CK) and Comparative Example 2 (i.e., LED white light). From the second to the eighth day of storage, the yellowing index of papaya fruits treated with Example 1 (i.e., LED blue light) remained significantly lower than that of papaya fruits treated with Comparative Example 1 (i.e., CK) and Comparative Example 2 (i.e., LED white light). It can also be seen that throughout the entire storage period, the yellowing rate of papaya fruits treated with Example 1 (i.e., LED blue light) was slower than that of papaya fruits treated with Comparative Example 1 (i.e., CK) and Comparative Example 2 (i.e., LED white light). Papaya fruits treated with Examples 2 and 3 showed similar results to those treated with Example 1.

[0147] The above results indicate that LED blue light irradiation treatment delayed the yellowing of papaya fruits.

[0148] (2) Results of colorimetric measurement

[0149] like Figure 2 As shown in Figure A, the brightness of papaya fruits in each treatment gradually increased with prolonged storage time. On days 2, 6, and 8 of storage, the peel brightness of papaya fruits treated with Example 1 (i.e., LED blue light) was significantly lower than that of papaya fruits treated with Comparative Example 1 (i.e., CK) and Comparative Example 2 (i.e., LED white light). Papaya fruits treated with Examples 2 and 3 showed similar results to those in Example 1.

[0150] like Figure 2As shown in Figure B, the color saturation of the papaya peel treated by different methods increased with the extension of storage time. In the early stage of storage (days 0-4), the color saturation of the papaya peel treated with Example 1 (i.e., LED blue light) was not significantly different from that of Comparative Example 1 (i.e., CK), but was significantly lower than that of the papaya peel treated with Comparative Example 2 (i.e., LED white light). In the 6th-8th day of storage, the color saturation of the papaya peel treated with Example 1 (i.e., LED blue light) was significantly lower than that of the papaya peel treated with Comparative Example 1 (i.e., CK) and Comparative Example 2 (i.e., LED white light). The papaya peels treated with Examples 2 and 3 showed similar results to those of Example 1.

[0151] like Figure 2 As shown in C, the chromaticity angle of papaya fruits treated by different methods gradually decreased with the extension of storage time. Among them, the chromaticity angle of papaya fruits treated with Example 1 (i.e., LED blue light) was consistently significantly smaller than that of papaya fruits treated with Comparative Example 1 (i.e., CK) and Comparative Example 2 (i.e., LED white light). The papaya fruits treated with Examples 2 and 3 showed similar results to those of Example 1.

[0152] The above results indicate that LED blue light irradiation can slow down the increase in brightness and color saturation of papaya fruit, while also slowing down the decrease in chromaticity angle of papaya fruit.

[0153] (3) Results of hardness measurement

[0154] like Figure 3 As shown, during the first 6 days of storage, the decrease in firmness of papaya fruits treated by different methods was not significant; on the 8th day of storage, the firmness of papaya fruits treated with Example 1 (i.e., LED blue light) was 126.80 N / cm. 2 The hardness of the papaya fruit treated with control example 1 (CK) was significantly higher than that of the papaya fruit treated with control example 1 (39.22 N / cm). 2 Papaya fruits treated with LED white light (hardness 121.44 N / cm) and Comparative Example 2 (i.e., LED white light) were compared. 2 On the 10th day of storage, the papaya fruit treated with Comparative Example 2 (i.e., LED white light) had a hardness as low as 31.33 N / cm. 2 The hardness of the papaya fruit treated with Example 1 (i.e., LED blue light) was 126.80 N / cm. 2 The levels remained high. The papaya fruits treated in Examples 2 and 3 showed similar results to those in Example 1.

[0155] The above results indicate that LED blue light irradiation significantly slows down the decrease in firmness of papaya fruits.

[0156] (4) Results of respiratory rate measurement

[0157] like Figure 4 As shown, papaya fruits treated by different methods all showed a peak in respiration release on the 6th day of storage. The respiration rates of papaya fruits treated with Example 1 (i.e., LED blue light) and Comparative Example 2 (i.e., LED white light) were significantly lower than those treated with Comparative Example 1 (i.e., CK). There was no significant difference in the respiration rates of papaya fruits treated with Example 1 (i.e., LED blue light) and Comparative Example 2 (i.e., LED white light).

[0158] The papaya fruits treated in Examples 2 and 3 showed similar results to those in Example 1.

[0159] The above results indicate that LED blue light irradiation treatment reduced the peak respiration rate of papaya fruits, thus inhibiting fruit respiration.

[0160] (5) Results of malondialdehyde content determination

[0161] like Figure 5 As shown, during storage, the malondialdehyde (MDA) content in papaya fruits treated with Comparative Example 1 (CK) and Comparative Example 2 (LED white light) showed an increasing trend, while the MDA content in papaya fruits treated with Example 1 (LED blue light) remained basically unchanged, with a relatively gentle change, and was significantly lower than that in papaya fruits treated with Comparative Example 1 (CK) and Comparative Example 2 (LED white light). The papaya fruits treated with Examples 2 and 3 showed similar results to those in Example 1.

[0162] The above results indicate that LED blue light irradiation effectively inhibits the accumulation of malondialdehyde in papaya fruit, reduces cell membrane damage, maintains the integrity of the fruit membrane, and thus delays the senescence process of the fruit.

[0163] (6) Results of superoxide dismutase activity assay

[0164] like Figure 6 As shown, during storage, the superoxide dismutase (SOD) activity of papaya fruits treated by different methods generally showed a gradual upward trend. The SOD activities of papaya fruits treated with Example 1 (i.e., LED blue light) and Comparative Example 2 (i.e., LED white light) were significantly lower than those treated with Comparative Example 1 (CK). There was no significant difference in SOD activity between the papaya fruits treated with Example 1 (i.e., LED blue light) and Comparative Example 2 (i.e., LED white light). The papaya fruits treated with Examples 2 and 3 showed similar results to those of Example 1.

[0165] The above results indicate that LED blue light irradiation treatment increased the activity of superoxide dismutase in papaya fruits during storage, effectively reducing cell peroxides and cell membrane damage.

[0166] (7) Results of flavonoid content determination

[0167] like Figure 7 As shown, on the second day of storage, the flavonoid content of papaya fruits treated by different methods all increased. The flavonoid content of papaya fruits treated with Example 1 (i.e., LED blue light) was significantly higher than that of papaya fruits treated with Comparative Example 1 (i.e., CK) and Comparative Example 2 (i.e., LED white light). From the second to the sixth day of storage, the flavonoid content of papaya fruits treated by different methods generally showed a decreasing trend, with the decrease being the smallest in the papaya fruits treated with Example 1 (i.e., LED blue light). On the eighth day of storage, the flavonoid content of papaya fruits treated by different methods all rebounded. Although the rebound in the flavonoid content of papaya fruits treated with Example 1 (i.e., LED blue light) was smaller, its flavonoid content was still significantly higher than that of the other two methods. On the tenth day of storage, the flavonoid content of the fruit treated with LED blue light decreased sharply, and the flavonoid content of the LED blue light group was higher than that of the LED white light group. The papaya fruits treated with Examples 2 and 3 showed similar results to those of Example 1.

[0168] The above results indicate that LED blue light irradiation treatment effectively maintains the flavonoid content of papaya fruit and improves the fruit's antioxidant capacity and quality.

[0169] (8) Results of determination of total phenol content

[0170] like Figure 8 As shown, during storage, the total phenolic content of papaya fruits treated by different methods generally showed a trend of first increasing and then decreasing, reaching its peak on the 6th day of storage. The peak total phenolic content of papaya fruits treated with Example 1 (i.e., LED blue light) was 0.17 mg / g fresh weight, the peak total phenolic content of papaya fruits treated with Comparative Example 1 (i.e., CK) was 0.15 mg / g fresh weight, and the peak total phenolic content of papaya fruits treated with Comparative Example 2 (i.e., LED white light) was 0.16 mg / g fresh weight. Throughout the entire storage period, the total phenolic content of papaya fruits treated with Example 1 (i.e., LED blue light) was significantly higher than that of papaya fruits treated with Comparative Example 1 (i.e., CK) and Comparative Example 2 (i.e., LED white light). The papaya fruits treated with Examples 2 and 3 showed similar results to those of Example 1.

[0171] The above results indicate that LED blue light irradiation significantly increases the total phenolic content of papaya fruit and effectively slows down the decline of total phenolic content in the later stages of storage, thereby improving the fruit's antioxidant capacity and quality.

[0172] (9) Results of determination of reduced ascorbic acid content

[0173] like Figure 9 As shown, with prolonged storage time, the content of reduced ascorbic acid in papaya fruits treated by different methods gradually increased. From day 2 to day 8 of storage, the content of reduced ascorbic acid in papaya fruits treated with Example 1 (i.e., LED blue light) was consistently significantly lower than that in papaya fruits treated with Comparative Example 1 (i.e., CK) and Comparative Example 2 (i.e., LED white light). The papaya fruits treated with Examples 2 and 3 showed similar results to those in Example 1.

[0174] The above results indicate that LED blue light irradiation can inhibit the increase of reduced ascorbic acid content in papaya fruit and delay the ripening process.

[0175] (10) Results of chitinase activity assay

[0176] like Figure 10 As shown, the chitinase activity in papaya fruits treated by different methods generally showed a trend of first increasing and then decreasing. In the early stage of papaya fruit storage (days 0-4), there was no significant difference in chitinase activity among papaya fruits treated by different methods. From day 6 of storage, the chitinase activity of papaya fruits treated with Example 1 (i.e., LED blue light) was significantly higher than that of papaya fruits treated with Comparative Example 1 (i.e., CK) and Comparative Example 2 (i.e., LED white light). The papaya fruits treated with Examples 2 and 3 showed similar results to those in Example 1.

[0177] The above results indicate that LED blue light irradiation treatment can significantly increase the chitinase activity of papaya fruit in the later stages of storage, thereby enhancing the fruit's ability to resist pathogen infection.

[0178] (11) Results of polygalacturonase activity assay

[0179] like Figure 11 As shown, during the storage period, the polygalacturonase activity in papaya fruits treated by different methods all showed a gradual increasing trend. Specifically, the polygalacturonase activity of papaya fruits treated with Comparative Example 1 (CK) and Comparative Example 2 (LED white light) changed slowly during the first 4 days of storage, while the polygalacturonase activity of papaya fruits treated with Example 1 (LED blue light) changed slowly during the first 6 days of storage. Throughout the entire storage period, the polygalacturonase activity of papaya fruits treated with Example 1 (LED blue light) was significantly lower than that of papaya fruits treated with Comparative Example 1 (CK) and Comparative Example 2 (LED white light). The papaya fruits treated with Examples 2 and 3 showed similar results to those of Example 1.

[0180] The above results indicate that LED blue light irradiation can slow down the increase of polygalacturonase activity in papaya fruit and delay the ripening of papaya fruit.

[0181] (12) Results of the determination of pectin lyase activity

[0182] like Figure 12 As shown, during the storage period, the pectin lyase activity in papaya fruits treated by different methods generally showed a trend of first increasing and then decreasing, reaching its peak on the 8th day of storage. The pectin lyase activity of papaya fruits treated with Example 1 (i.e., LED blue light) was significantly lower than that of papaya fruits treated with Comparative Example 1 (i.e., CK) and Comparative Example 2 (i.e., LED white light). The papaya fruits treated with Examples 2 and 3 showed similar results to those of Example 1.

[0183] The above results indicate that LED blue light irradiation can slow down the increase in pectin lyase activity in papaya fruit, maintain fruit firmness, and thus delay fruit softening.

[0184] Based on the results of the above 12 physiological indicators, it was confirmed that LED blue light irradiation treatment delayed the yellowing of papaya peel, effectively maintained fruit firmness, significantly reduced the peak respiration rate, inhibited papaya fruit respiration, improved the antioxidant capacity, defense capacity and resistance of papaya fruit, and inhibited fruit cell wall degradation.

[0185] Application Example 2: Effects of LED Lighting on Other Climax Fruits

[0186] I. The Effects of LED Lighting on Banana Fruit

[0187] 1. Experimental Methods

[0188] Bananas (Musa acuminata AAA Cavendish subgroup, 'Baxijiao') were used as the experimental subject. After conventional harvesting, cleaning and disinfection, the banana fruits were randomly divided into two groups with three replicates in each group. They were treated and stored according to the "light control" method in Example 1 and Comparative Example 1, respectively. The only difference was that the storage temperature was 22°C, which is the optimal storage temperature for bananas.

[0189] The bananas were stored for 17 days. The bananas treated by different methods were photographed periodically, and the color (i.e., brightness, color saturation and color angle value) and firmness of the bananas were measured according to the method in Application Example 1.

[0190] 2. Experimental Results

[0191] like Figure 13 As shown, the bananas treated with Example 1 (i.e., LED blue light) began to change color on the 10th day of storage, and turned yellow by the 15th day, while the bananas treated with Comparative Example 1 (i.e., CK) remained green on the 17th day of storage.

[0192] like Figure 14 As shown in Figures A through C, compared to Comparative Example 1 (darkness), bananas treated with Example 1 (blue light) exhibited higher overall brightness and color saturation, and lower chromaticity angle values ​​during storage. This indicates that LED blue light irradiation treatment can promote an increase in the brightness and color saturation of bananas, while simultaneously promoting a decrease in the chromaticity angle.

[0193] like Figure 15 As shown, the firmness of bananas treated in Comparative Example 1 (i.e., darkness) hardly changed during storage, while the firmness of bananas treated in Example 1 (i.e., blue light) decreased significantly in the later stages of storage (days 13-14).

[0194] The above results indicate that using the light control method of the present invention to irradiate bananas, which are also climacteric fruits, with LED blue light actually promotes their ripening and fails to achieve the effect of preservation.

[0195] II. The Effects of LED Lighting on Banana Fruit

[0196] 1. Experimental Methods

[0197] Using the pink banana (Musa spp ABB Pisang Awak, Guangfen No. 1) as the experimental subject, after conventional harvesting, cleaning and disinfection, the pink banana fruits were randomly divided into 3 groups, with 3 replicates in each group. They were treated and stored according to the "light control" method in Example 1 and Comparative Examples 1-2, with the only difference being that the storage temperature was 27°C, which is the optimal storage temperature for pink bananas.

[0198] The banana fruits were stored for a total of 6 days. The fruits treated by different methods were photographed periodically, and the color (i.e., brightness, color saturation and color angle), firmness and respiration rate of the banana fruits were measured according to the method in Application Example 1.

[0199] 2. Experimental Results

[0200] like Figure 16 As shown, during storage, compared with Comparative Example 1 (i.e., darkness), the banana fruits treated with Example 1 (i.e., LED blue light) and Comparative Example 2 (i.e., LED white light) turned yellow 2 days earlier, and the yellowing speed was faster.

[0201] like Figure 17 As shown in A to C, compared with Comparative Example 1 (i.e., darkness), the bananas treated with Example 1 (i.e., LED blue light) and Comparative Example 2 (i.e., LED white light) had higher overall brightness and color saturation and lower chromaticity angle values ​​during storage, indicating that both LED blue light and LED white light irradiation treatments promoted the yellowing of banana fruits.

[0202] like Figure 18 As shown, from the second day of storage, the firmness of the bananas treated with Example 1 (i.e., LED blue light) and Comparative Example 2 (i.e., LED white light) was significantly higher than that of Comparative Example 1 (i.e., CK). This indicates that both LED blue light and LED white light irradiation treatments promoted the softening of the banana fruit.

[0203] like Figure 19 As shown, the respiration rates of bananas treated with Example 1 (i.e., LED blue light) and Comparative Example 2 (i.e., LED white light) were both higher than those of papayas treated with Comparative Example 1 (i.e., CK). The respiration peaks of bananas treated with Example 1 (i.e., LED blue light) and Comparative Example 2 (i.e., LED white light) occurred on the first and second days of storage, respectively, while the respiration peak of bananas treated with Comparative Example 1 (i.e., CK) showed an increasing trend during the storage period. This indicates that both LED blue light and LED white light irradiation treatments promoted the respiration of bananas.

[0204] The above results indicate that using the light control method of the present invention to irradiate the banana fruit, which also belongs to the climacteric fruit type, with LED blue light actually promotes its ripening and fails to achieve the effect of preservation.

[0205] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description and ideas, and it is neither necessary nor possible to exhaustively describe all implementation methods here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preserving papaya fruit, characterized in that, Papaya fruits are individually packaged in unsealed polyethylene film bags with a thickness of 0.01mm to 0.02mm and stored in a dark, lightless room. The papaya fruits are then irradiated with blue light from LEDs until the end of the storage process. No other light source is used during the process. Before processing, the papaya fruit is washed and disinfected; the papaya fruit is unripe before processing, and the standard for unripeness is as follows: according to "NY / T 691-2018 Papaya", the peel color is 5% to 15% turning yellow; The wavelength of the blue light is 430 nm to 470 nm, and the light intensity is 48 Lux to 52 Lux. The storage temperature is 24℃~26℃, and the humidity is 60%rh~80%rh.

2. The method according to claim 1, characterized in that, The intensity of the blue light is 49.5 Lux.

3. The method according to claim 1, characterized in that, The storage temperature is 25℃ and the humidity is 60%rh~80%rh.

4. The method according to claim 1, characterized in that, The storage temperature is 24℃~26℃ and the humidity is 70%rh.

5. The method according to claim 3 or 4, characterized in that, The storage temperature is 25℃ and the humidity is 70%rh.

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