Method for keeping kiwi fruits fresh through low-dose electron beam irradiation

Abstract

The invention discloses a method for keeping kiwi fruits fresh through low-dose electron beam irradiation. The method comprises the following steps: classifying and cleaning kiwi fruits, boxing in a single layer and fixing; irradiating by using an electron beam source with electron beam energy less than or equal to 10MeV, wherein the dose is 0.4-1.0 kGy; after irradiation, pre-cooling at a low temperature of 4 DEG C for 10-12 hours, the storage temperature being 1 + / -1 DEG C, and the relative humidity being greater than or equal to 90%; and moving the ex-warehouse fruits to a place with the temperature of 5-8 DEG C for 10 hours, and then ex-warehouse. According to the method, secondary boxing of fresh keeping and market selling is avoided through boxing in advance, and the working procedures are reduced. And the electron beam irradiation process is simple. The cold storage temperature after preservation avoids damage to kiwi fruit protoplast caused by cold storage at 0 DEG C so as not to affect the taste. The fresh-keeping time of the kiwi fruits can reach 120-150 days, the fresh-keeping time is long, and the requirements of food health and safety are met.

Description

Technical Field

[0001] The invention relates to the technical field of food preservation, in particular to a method for preserving kiwifruit by low-dose electron beam irradiation. Background Art

[0002] Kiwi fruit is a nutritious fruit rich in vitamin C, cellulose and trace elements. However, since kiwi fruit is easily affected by seasons and has a short shelf life, the preservation of different kiwi fruits needs to be solved urgently. At present, common preservation methods include refrigerated preservation, controlled atmosphere preservation, heat treatment, chemical preservation and biological preservation. Sterilization preservation, etc. Refrigerated preservation alone can extend the shelf life by about 40 days, and refrigerated and controlled atmosphere preservation can extend it by up to 6 months, but the requirements for the storage environment are very high and the price is high. Heat treatment can easily reduce the taste of kiwi fruit. Chemical preservation needs to ensure the safety and effectiveness of the reagents. Biological preservation is the preservation of kiwi fruit using microorganisms and their metabolites, which can reduce the respiration intensity of the fruit, delay the ripening and decay process, and maintain the freshness and nutritional content of the fruit. These current methods can extend the shelf life of kiwi fruit to a certain extent, but there are differences in the freshness, taste and nutritional content of the fruit.

[0003] The principle of irradiation sterilization: irradiation sterilization is a process that uses radioactive rays to disinfect and preserve food. Radioactive rays, such as gamma rays or X-rays, can penetrate the surface of objects and kill bacteria, viruses, parasites, etc. inside, thereby extending the shelf life of food. Irradiation treatment has some obvious advantages. First, it can effectively extend the shelf life of food and improve food safety. Secondly, irradiation sterilization is a non-chemical treatment sterilization method that does not add any chemicals, so it will not negatively affect the taste and nutritional content of food. In addition, irradiation treatment is a cold processing method that can be carried out at room temperature and will not change the original temperature and texture of the irradiated object.

[0004] Those skilled in the art have provided a method for extending the shelf life of kiwifruit using electron beam irradiation technology to solve the problems raised in the above background technology. Summary of the invention

[0005] The object of the present invention is to provide a method for preserving irradiated kiwifruit, which can effectively prolong the shelf life of kiwifruit and maintain its quality. The method has no radiation residue, fast processing speed, wide processing range and significant processing effect.

[0006] The irradiated kiwifruit preservation method of the present invention comprises the following steps:

[0007] 1. Select the kiwifruit obtained during the fruit picking period and remove the damaged and diseased fruits;

[0008] 2. Pack the selected kiwifruits into single-layer boxes and use the same packaging directly for subsequent shipment, thus avoiding damage and formalities caused by secondary packaging and simplifying the preservation and shipment process;

[0009] 3. Irradiate the packed kiwifruit with an electron beam. The energy of the electron accelerator is ≤10MeV and the dose is controlled between 0.4 and 1.0 kGy.

[0010] 4. After irradiation, the fruit should be pre-cooled at 4℃ for 10-12h and then transferred to cold storage for preservation. The storage temperature should be 1±1℃, the relative humidity should be ≥90%, and the core temperature should be 1-2℃.

[0011] 5. Before the irradiated and refrigerated boxed kiwifruits are shipped out of the warehouse, the fruits should be moved to a place with a temperature of 5-8℃ for 10 hours before being shipped out for sale.

[0012] Through the above steps, the present invention can effectively extend the shelf life of kiwi fruit and maintain its quality. Experimental results show that by adopting the preservation method of the present invention, the shelf life of kiwi fruit can be extended to more than 120 days, and the appearance of kiwi fruit does not change significantly, the loss of nutrients such as vitamin C is small, and the taste does not change significantly.

[0013] The irradiated kiwifruit preservation method of the present invention has the following advantages:

[0014] 1. The kiwifruit is directly irradiated after packaging, without the need for secondary packaging;

[0015] 2. The dose of electron beam irradiation preservation is only 0.4-1.0 kGy, which is very small, consumes little energy and is cheap.

[0016] 3. Electron beam irradiation preservation is carried out directly in the electron beam irradiation processing plants currently available on the market. No other accessories are required, the process is simple, and the irradiation efficiency is high.

[0017] 4. It is a cold processing method, which has no obvious effect on the nutrition and taste of kiwifruit, but compared with refrigeration alone, the spoilage rate is reduced and the shelf life can be more effectively extended.

[0018] 5. Suitable for irradiation preservation of various kiwifruits. DETAILED DESCRIPTION

[0019] The present invention is described in detail below in conjunction with two embodiments:

[0020] Example 1:

[0021] Select Hongyang kiwifruit picked in Cangxi County, Sichuan Province, and remove the damaged and diseased fruits.

[0022] The selected kiwifruits are packed in 40×50×6cm cartons with foam fixation. The cartons are fixed with foam so that each kiwifruit lies flat in the carton, and the carton openings are sealed and packed to prevent shaking and squeezing during transportation.

[0023] The whole box of kiwifruit is directly placed on the beam device of the electron beam irradiation device for irradiation treatment. The electron beam generated by the high-voltage electron beam device with a ray of 10MeV is controlled at a dose of 0.4 to 2.0 kGy. This step is an important part of the present invention. The specific irradiation process is as follows:

[0024] (1) Setting irradiation parameters: Before starting the irradiation process, it is necessary to set the irradiation parameters according to the required preservation effect and safety. These parameters include irradiation energy, dosage, irradiation time, etc.

[0025] (2) Kiwifruit placement: Place a box of kiwifruit in a single layer on the under-beam device in the work area outside the irradiation area. The under-beam device is activated to carry the kiwifruit into the maze in the irradiation area and then transported out. Single-layer placement ensures that the kiwifruit can be evenly irradiated by the electron beam on all four sides.

[0026] (3) Electron beam irradiation: Start the irradiation device and the under-beam device. When the under-beam device moves to the irradiation area, the kiwifruit begins to be irradiated. During this process, the rays will penetrate the skin and flesh of the kiwifruit, disinfecting and preserving the inside.

[0027] (4) Dose monitoring and control: During the irradiation process, the irradiation of kiwifruit needs to be monitored in real time to ensure that it reaches the predetermined irradiation dose. If any abnormality is found, such as too high or too low radiation dose, the irradiation parameters need to be adjusted in time. The irradiation doses are 0.4-1.0 kGy, 1.0-1.5 kGy, and 1.5-2.0 kGy respectively.

[0028] (5) End of irradiation: When the predetermined irradiation dose is reached, the boxed kiwifruit is removed from the beam-down device.

[0029] (6) Refrigerated preservation: After irradiation, the fruits are pre-cooled at 4°C for 10 to 12 hours and then transferred to a cold storage for refrigerated preservation. The storage temperature is 1±1°C, the relative humidity is ≥90%, and the core temperature is 1 to 2°C.

[0030] (7) Quality monitoring during cold storage: Randomly sample the Hongyang kiwifruit stored at low temperatures after irradiation every two weeks to measure its color, firmness, soluble solids, decay rate, and chilling damage to evaluate the storage conditions at different times.

[0031] (8) Evaluation of irradiation process: A comparative analysis was conducted on kiwifruit samples treated with irradiation doses of 0.4-1.0 kGy, 1.0-1.5 kGy, and 1.5-2.0 kGy, and the correlation between the spoilage rate and shelf life of Hongyang kiwifruit and the irradiation process was analyzed.

[0032] (9) Result analysis: The experimental data showed that the kiwifruit samples treated with irradiation doses of 0.4-1.0 kGy were superior to those treated with 1.0-1.5 kGy and 1.5-2.0 kGy in terms of shelf life extension and soluble solids. When the irradiation dose was 0.4-1.0 kGy, the shelf life could be extended by more than 120 days, while the shelf life of the kiwifruit in the same batch that was not irradiated and stored in cold storage was extended by 60-90 days. Therefore, electron beam irradiation can effectively extend the shelf life.

[0033] (10) Product delivery: Before the irradiated and refrigerated kiwifruit is shipped out of the warehouse, the fruit is first moved to a place with a temperature of 5-8°C for 10 hours before being shipped out for sale. No secondary packaging is required.

[0034] Example 2:

[0035] Select Hongshi No. 2 kiwifruit picked in Mianzhu City, Sichuan Province, and remove the damaged and diseased fruits.

[0036] The selected kiwifruits are packed in 50×70×7cm cartons with foam fixation. The cartons are fixed with foam so that each kiwifruit lies flat in the carton, and the carton openings are sealed and packed to prevent shaking and squeezing during transportation.

[0037] The whole box of kiwifruit is directly placed on the beam device of the electron beam irradiation device for irradiation treatment. The electron beam generated by the high-voltage electron beam device with a ray of 10MeV is controlled at a dose of 0.4 to 2.0 kGy. This step is an important part of the present invention. The specific irradiation process is as follows:

[0038] (1) Setting irradiation parameters: Before starting the irradiation process, it is necessary to set the irradiation parameters according to the required preservation effect and safety. These parameters include irradiation energy, dosage, irradiation time, etc.

[0039] (2) Kiwifruit placement: Place a box of kiwifruit in a single layer on the under-beam device in the work area outside the irradiation area. The under-beam device is activated to carry the kiwifruit into the maze in the irradiation area and then transported out. Single-layer placement ensures that the kiwifruit can be evenly irradiated by the electron beam on all four sides.

[0040] (3) Electron beam irradiation: Start the irradiation device and the under-beam device. When the under-beam device moves to the irradiation area, the kiwifruit begins to be irradiated. During this process, the rays will penetrate the skin and flesh of the kiwifruit, disinfecting and preserving the inside.

[0041] (4) Dose monitoring and control: During the irradiation process, the irradiation of kiwifruit needs to be monitored in real time to ensure that it reaches the predetermined irradiation dose. If any abnormality is found, such as too high or too low radiation dose, the irradiation parameters need to be adjusted in time. The irradiation doses are 0.4-1.0 kGy, 1.0-1.5 kGy, and 1.5-2.0 kGy respectively.

[0042] (5) End of irradiation: When the predetermined irradiation dose is reached, the boxed kiwifruit is removed from the beam-down device.

[0043] (6) Refrigerated preservation: After irradiation, the fruits are pre-cooled at 4°C for 10 to 12 hours and then transferred to a cold storage for refrigerated preservation. The storage temperature is 1±1°C, the relative humidity is ≥90%, and the core temperature is 1 to 2°C.

[0044] (7) Quality monitoring during cold storage: Randomly sample the Hongyang kiwifruit stored at low temperatures after irradiation every two weeks to measure its color, firmness, soluble solids, decay rate, and chilling damage to evaluate the storage conditions at different times.

[0045] (8) Evaluation of irradiation process: A comparative analysis was conducted on kiwifruit samples treated with irradiation doses of 0.4-1.0 kGy, 1.0-1.5 kGy, and 1.5-2.0 kGy, and the correlation between the spoilage rate and shelf life of Hongyang kiwifruit and the irradiation process was analyzed.

[0046] (9) Result analysis: The experimental data showed that the kiwifruit samples treated with irradiation doses of 0.4-1.0 kGy were superior to those treated with 1.0-1.5 kGy and 1.5-2.0 kGy in terms of shelf life extension and soluble solids. When the irradiation dose was 0.4-1.0 kGy, the shelf life could be extended by more than 120 days, while the shelf life of the kiwifruit in the same batch that was not irradiated and stored in cold storage was extended by 60-90 days. Therefore, electron beam irradiation can effectively extend the shelf life.

[0047] (10) Product delivery: Before the irradiated and refrigerated kiwifruit is shipped out of the warehouse, the fruit is first moved to a place with a temperature of 5-8°C for 10 hours before being shipped out for sale. No secondary packaging is required.

Claims

1. A method for preserving kiwifruit by low-dose electron beam irradiation, characterized in that: The following steps are involved: The kiwifruits are selected and packed in single-layer boxes during the picking period. They are irradiated with electron beams, and the irradiation dose is controlled between 0.4 and 1.0 kGy. The irradiated kiwifruits are refrigerated for preservation.

2. The method for preserving irradiated kiwifruit according to claim 1, characterized in that: The packaging is a single-layer carton packaging.

3. The method for preserving irradiated kiwifruit according to claim 1, characterized in that: The energy of the electron accelerator is ≤10 MeV.

4. The method for preserving irradiated kiwifruit according to claim 1, characterized in that: The irradiation dose is between 0.4 and 1.0 kGy.

5. The method for preserving irradiated kiwifruit according to claim 1, characterized in that: The temperature of the refrigerated preservation is 1±1°C.