Dried persimmon preservation method capable of accelerating frosting and prolonging storage period

Abstract

The invention discloses a dried persimmon storage method capable of accelerating frosting and prolonging storage period, which comprises the following steps: accelerating the frosting of dried persimmons by adopting periodic temperature change control, performing ozone fumigation after the surface frosting area of the dried persimmons is greater than 90%, then loading the dried persimmons into a packaging bag containing an oxygen absorbent, and sealing the packaging bag. Mixed gas of 80%-90% of carbon dioxide and 10%-20% of nitrogen is adopted for controlled atmosphere bag sealing, and finally ultraviolet irradiation is conducted. According to the method disclosed by the invention, the dried persimmons are accelerated to frost by utilizing variable-temperature period control and combined with a novel dried persimmon air conditioning technology, so that oxidation and spoilage which are easy to occur in the storage period of the dried persimmons are effectively slowed down, the dried persimmons can be manually controlled to frost quickly after being harvested, and pollution in the frosting process is reduced so as to improve the frosting quality; and the taste and the nutritional value of the dried persimmons can be maintained for a longer time after the dried persimmons are stored for a long time by utilizing a targeted controlled atmosphere technology.

Description

Technical Field

[0001] The invention belongs to the technical field of dried persimmon processing, and in particular relates to a dried persimmon preservation method capable of accelerating frost removal and prolonging storage period. Background Art

[0002] Persimmon cake refers to a dried persimmon product made from fresh persimmons and processed through a series of drying processes with a water content of about 40%. Persimmon cake is rich in nutrients, and contains a wealth of vitamin A, vitamin C, potassium, calcium, iron and other minerals, as well as dietary fiber. Compared with other dried fruit products, persimmon cake has the characteristics of high water content, high sugar content, and easy contamination of the skin. After traditional artificially dried persimmon cakes are removed from production, they are often restricted by storage conditions or improper storage methods during the storage process, and are prone to quality deterioration. During storage, especially during the traditional frosting process, they are more susceptible to microbial contamination, leading to corruption, dehydration, browning and other problems.

[0003] Faced with the problem of persimmon cakes being difficult to control due to frost, which leads to contamination and easy deterioration during storage, the processing and storage of persimmon cakes currently urgently need to find a more effective and low-cost storage technology to extend the shelf life in order to maintain the original flavor quality and nutritional value of the persimmon cake products and maintain the processing performance of the persimmon cakes. Summary of the invention

[0004] The purpose of the present invention is to provide a persimmon preservation method for accelerating frost release and extending the storage period. The method utilizes variable temperature cycle control to accelerate frost release from persimmons and combines a novel persimmon gas conditioning technology to effectively slow down oxidation and corruption and deterioration that are prone to occur during storage, so that the persimmons can be artificially controlled to release frost quickly after harvest and reduce pollution during the frost release process. In addition, targeted gas conditioning technology is utilized to maintain the taste and nutritional value of the persimmons for a longer period of time after long-term storage.

[0005] The method for preserving dried persimmons for accelerating frost removal and prolonging storage period provided by the present invention comprises the following steps:

[0006] Step 1: Dried persimmon processing

[0007] Around the Frost Descent solar term, select persimmons, peel them and hang them in a ventilated and cool place. When the moisture content of the persimmons reaches 38% to 43%, the inside of the fruit becomes soft and the outside becomes hard, knead them by hand to make the texture uniform inside and outside, and shape them into spindle-shaped persimmon cakes. Then select persimmon cakes with flat surfaces and no cracks, cut off the fruit stalks and sepals, and use a brush to clean impurities adhering to the surface of the persimmon cakes.

[0008] Step 2: Quickly frost the dried persimmon

[0009] The dried persimmons processed in step 1 are placed in a precooling room at 0 to 2°C for precooling, and then transferred to a frost removal room for temperature control during the frost removal period. The temperature control method is as follows: gradually lowering the temperature in the frost removal room from -5 to -3°C to -13 to -11°C, and controlling the cooling time to last for 90 to 100 minutes; then gradually raising the temperature in the frost removal room to -5 to -3°C, and controlling the heating time to last for 80 to 90 minutes, thus completing one cycle, and the same cycle lasts for 170 to 190 minutes in total. For the same batch of dried persimmons, the temperature control is continuously cycled for more than 16 cycles until the frosting area on the surface of the dried persimmons is greater than 90%.

[0010] Step 3: Ozone treatment

[0011] The dried persimmons with a surface frosting area greater than 90% obtained in step 2 are placed in a single polypropylene hard spindle-shaped tray, the dried persimmons with the tray are stacked on the fence, and transferred to a circulating ventilation fumigation box, and the concentration of ozone gas in the fumigation box is maintained at 30-35 mg / m 3 The fumigation time lasts for 30 to 40 minutes, the ambient temperature in the box is maintained at 17±3℃, and the relative humidity is maintained at 55±5%, ensuring that the ozone gas circulates through the purification system air duct during the fumigation period and the ozone gas is evenly distributed between the dried persimmons.

[0012] Step 4: Pack dried persimmons into bags

[0013] The persimmons treated with ozone in step 3 are taken out of the fumigation box, and the persimmons are individually bagged in a sterile operating room, and an oxygen absorber wrapped in a non-woven bag is placed in the packaging bag.

[0014] Step 5: Modified atmosphere sealing bag

[0015] Place the packaging bag filled with dried persimmons in step 4 in a modified atmosphere packaging machine, first degas for 15 to 20 seconds at a vacuum degree of 90 to 95 kPa to exhaust the air in the bag, and then fill it with a mixed gas of carbon dioxide and nitrogen, wherein the volume percentage composition of the mixed gas is: 80% to 90% carbon dioxide and 10% to 20% nitrogen. The bag is sealed after the pressure of the mixed gas in the bag reaches 0.08 to 0.09 MPa.

[0016] Step 6: UV exposure

[0017] Spread the dried persimmons packed in the air bag in step 5 in the UV irradiation chamber and irradiate with UV lamp with a wavelength of 240-280nm. The UV lamp is 0.8-1.2m away from the surface of the packaging bag and the irradiation intensity is 140-160μW / cm 2 The irradiation time is 20 to 40 minutes.

[0018] Preferably, in the above step 2, the variable temperature control method is: gradually cooling the temperature of the frost outlet room from -4°C to -12°C, and the cooling time is controlled to last for 90 to 100 minutes; then gradually heating the temperature of the frost outlet room to -4°C, and the heating time is controlled to last for 80 to 90 minutes, so that one cycle ends, and the same cycle is 180 minutes in total.

[0019] Preferably, in the above step 3, the fumigation time lasts for 30 minutes.

[0020] Preferably, in the above step 4, a polyethylene / polyamide composite plastic bag with a double-side thickness of 0.16 to 0.20 mm and a side length of 10 to 12 cm is used to package the dried persimmons.

[0021] Preferably, in the above step 4, the oxygen absorber comprises the following components in percentage by mass: 55% to 65% iron powder, 5% to 10% activated carbon, 15% to 25% calcium carbonate, and 5% to 10% sodium bicarbonate.

[0022] Preferably, in the above step 5, the volume percentage composition of the mixed gas is: 85% carbon dioxide and 15% nitrogen.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1. The present invention performs periodic temperature control on the frost of dried persimmons, which greatly shortens the frost cycle of dried persimmons, improves the frost quality and reduces the impact of the environment on frost. The traditional frost method of dried persimmons often relies on the slow change of natural environment temperature, and the frost process takes a long time. The periodic temperature control can accurately adjust the temperature change cycle, and accelerate the migration of water and the precipitation of sugar inside the dried persimmons by artificially setting the appropriate temperature change range and frequency, thereby significantly shortening the frost cycle. Accurate periodic temperature control can also ensure that the frost process of dried persimmons is more uniform. The surface of the dried persimmons can be orderly adjusted to the dynamic balance of water and sugar under a suitable temperature environment. The dried persimmon frost layer produced in this way is white, delicate and evenly distributed on the surface of the dried persimmons. The periodic temperature control method is carried out in a relatively closed control box, which reduces the interference of adverse external climate (such as large humidity changes, sudden cooling, etc.) on the frost process. This can not only stabilize the frost effect, but also reduce the risk of dried persimmon damage caused by weather changes, and improve the qualified rate of products.

[0025] 2. The novel gas ratio adopted in the present invention regulates the gas composition inside the dried persimmon packaging scientifically and accurately and combines it with optimized packaging materials. The dried persimmon is stored in a controlled atmosphere using a mixed gas ratio of high-concentration carbon dioxide (80% to 90%) and nitrogen (10% to 20%). When the dried persimmon is in a high-concentration carbon dioxide storage environment, the growth and reproduction of microorganisms on the dried persimmon is greatly inhibited by changing the gas balance inside and outside the microbial cells, the growth rate of mold is significantly reduced, and the hyphae grow slowly or even stop, which greatly reduces the risk of dried persimmon being contaminated by mold. In addition, the activity of respiratory enzymes in dried persimmon cells is inhibited. The key enzymes of respiration, such as cytochrome oxidase, etc., will change their structure and activity in a high-concentration carbon dioxide environment, and the consumption rate of nutrients inside the dried persimmon will be greatly slowed down. This storage method overcomes the limitation of the short storage period of traditional packaging methods and can provide the best preservation effect for dried persimmon. This controlled atmosphere technology provides an efficient and controllable solution for the storage of persimmon cakes, extending the storage period of persimmon cakes and maintaining their optimal edible quality. At the same time, it significantly extends the shelf life of the product and provides more powerful technical support for the development of the persimmon cake industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a fast defrosting cycle temperature control (-4~-12℃).

[0027] Figure 2 It is the frost area of ​​dried persimmon under the control of different temperature range cycles.

[0028] Figure 3 The effect of ozone treatment at different times on the total colony count of dried persimmon.

[0029] Figure 4 It is the total bacterial count of dried persimmons stored in different atmosphere control ratios for 90 days.

[0030] Figure 5 It is the total number of molds in dried persimmons stored with different atmosphere control ratios for 90 days.

[0031] Figure 6 It is the hardness of persimmons stored in different packaging.

[0032] Figure 7 It is the total acidity of dried persimmons stored in different packages.

[0033] Figure 8 It is the moisture content of dried persimmons stored in different packages.

[0034] Fig. 9 It is the effect of ultraviolet treatment at different times on the color difference of dried persimmons.

[0035] Fig.10 This is a photo of the dried persimmon product obtained by the method of Example 1.

[0036] Fig.11This is a photo of the dried persimmon obtained by the comparative method. DETAILED DESCRIPTION

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0038] In order to determine the process conditions of the present invention, the inventors conducted a large number of laboratory research experiments, and the specific experiments are as follows:

[0039] 1. Determination of the temperature range for controlling the frosting of dried persimmon

[0040] By implementing the environmental temperature cycle adjustment and control, the frosting process of persimmons can be accelerated, and the processing time consumed by the traditional frosting method of persimmons can be greatly shortened. By comparing the frosting effects of persimmons under cycle control in different temperature ranges within the same time, the appropriate temperature control range can be selected. Persimmons with uniform texture and size are selected, and the frosting experiment of persimmons is carried out in different temperature ranges, that is, five temperature difference fluctuation gradient groups of 7 to -9°C, -6 to -10°C, -5 to -11°C, -4 to -12°C, and -3 to -13°C are selected for the experiment. A constant temperature of -8°C is used as a control, and a temperature drop and rise fluctuation control is carried out for a total of 180 minutes per cycle (that is, every 180 minutes in the temperature range is a cycle, and in one cycle the temperature first drops from the highest temperature to the lowest temperature, and then rises from the lowest temperature to the highest temperature. Taking -4 to -12°C as an example, the specific temperature change control process is as follows Figure 1 16 cycles were performed continuously for a total of 48 hours. Then, 1 cm × 1 cm samples were cut from the skin of the dried persimmons in each group, and the area covered by the persimmon frost was calculated using a transparent counting plate. Three parallel results were performed for each group and the average was taken. Figure 1 The results show that with the increase of temperature difference between each group, the frosting area of ​​persimmon cake gradually increases. When -4~-12℃ is used for periodic cycle control, the frosting area of ​​persimmon cake can reach 93%, which can meet the requirements of finished products. Further increasing the temperature difference has little effect on the results but increases the cost. Therefore, the best choice is the variable temperature control scheme of -4~-12℃.

[0041] 2. Determination of ventilation time for ozone treatment

[0042] Ozone ventilation treatment of dried persimmons can play a role in sterilization, mildew prevention and disinfection. When ozone ventilation is used to fumigate dried persimmons, ozone concentration and treatment time are important parameters, and a reasonable ratio is required to achieve the best preservation effect. Select dried persimmons after frost to conduct ozone sterilization experiments. Place the dried persimmons in the test box, connect the ozone generator to the test box to form a gas passage, and adjust the ozone supply concentration to 30-35 mg / m 3The treatments were performed for 10, 20, 30 and 40 min respectively. Untreated fresh dried persimmons were used as controls. The total number of bacterial colonies on the surface of dried persimmons in each treatment group was determined. Three parallel tests were performed for each group and the results were averaged. Figure 3 The results showed that when persimmon cake was under constant ozone gas treatment conditions, the total number of microbial colonies on the surface of persimmon cake showed a downward trend with the extension of ozone ventilation time, and then tended to be stable. The effect of treating persimmon cake with ozone ventilation for 30 minutes was better.

[0043] 3. Determination of the ratio of carbon dioxide and nitrogen concentration in controlled atmosphere storage of dried persimmons

[0044] The growth and reproduction of microorganisms require a suitable gas environment. Carbon dioxide has an antibacterial effect and can interfere with the metabolic process of microbial cells. Nitrogen is an inert gas that mainly plays a filling role in the atmosphere control environment, reducing the aerobic environment required for microbial growth. The experiment explored the effects of different concentration ratios of carbon dioxide and nitrogen on the storage effect of dried persimmons. Fresh dried persimmons that had completely frosted were selected as raw materials. The dried persimmons were placed in atmosphere-controlled bags, and the air was vacuumed out. Ten concentration ratios of gas were selected for ventilation. Different concentration ratios of carbon dioxide and nitrogen were introduced into the bag until the pressure in the bag reached 0.08-0.09 MPa. The bags were then sealed and stored for 90 days to determine the total number of colonies and molds in the dried persimmons. The total colony count determination refers to the national standard GB4789.2-2022, and the mold and yeast count refers to the national standard GB4789.15-2016. Take three parallels in each group, weigh 25g of sample and put it into a conical flask containing 225mL of normal saline, place it for 30 minutes, shake it thoroughly to homogenize, perform 10-fold gradient dilution, select the sample solution with appropriate dilution, take 1mL of each and add it to sterile culture dishes, add 20mL of plate count agar medium and Bengal red agar medium to each dish, mix and culture, count the number of colonies in each dish, calculate the total number of bacterial colonies and the number of mold colonies, and analyze the effects of processing and storage methods on the hygiene and safety of dried persimmons. Results are as follows Figure 4 , Figure 5 .

[0045] Depend on Figure 4 and Figure 5 It can be seen that with the increase of carbon dioxide concentration and the decrease of N2 concentration, the total colony count and total mold count of persimmon cake showed a downward trend, indicating that carbon dioxide showed a stronger inhibitory effect on persimmon cake microorganisms under the storage conditions of higher concentration of carbon dioxide. After comprehensive consideration, a volume concentration ratio of 85% carbon dioxide and 15% nitrogen was selected for the atmosphere conditioning of persimmon cake.

[0046] 4. Storage experiment of dried persimmons in different packages

[0047] Persimmons are rich in nutrients such as water, sugar, and vitamins. They have problems such as short shelf life and easy deterioration during circulation and storage. The effects of different packaging methods on the storage of persimmons were explored, and different packaging methods were used to accelerate the storage experiment of persimmons, in order to provide a reference for the improvement of persimmon packaging. The finished persimmons were divided into groups and placed in polyethylene / polyamide composite plastic bags, and the persimmon packaging bags of each group were sealed after different treatments: the first vacuum packaging group: vacuuming, the vacuum degree was set to -0.1MPa; the second deoxidizer packaging group: built-in deoxidizer 5g, the mass percentage composition of the deoxidizer was: 60% iron powder, 5% sodium chloride, 25% calcium carbonate, 10% sodium bicarbonate; the third modified atmosphere packaging group: composite gas modified atmosphere filling bag, the composite gas volume percentage composition was: 85% carbon dioxide and 15% nitrogen, the inflation pressure was 0.08MPa; another control group was only bagged without treatment. Each group of persimmons was placed at a constant temperature of 35℃ for 90 days to measure the changes in persimmon surface hardness, total acid content, moisture content and other indicators. The persimmon skin hardness and pulp hardness were measured using a physical property tester. The test probe was a P / 2 probe, with a trigger force of 5.0g, a speed of 1.0mm / s before the test, a test speed of 1.0mm / s, a speed of 10.0mm / s after the test, and a displacement of 14mm. Three measurement sites were selected for each sample, and three parallels were selected for each group. The hardness and other indicators between groups were compared to evaluate the effects of different packaging methods on the texture characteristics of persimmons. The determination of total acid in persimmons refers to the national standard: GB5009.239-2016. The acid-base titration method is used for determination. Three parallels are selected for each group. About 10g of the persimmon samples after shredding and mixing are taken, crushed and homogenized, extracted with distilled water, filtered with a vacuum pump, fixed to 100mL, filtered, and 10mL of the filtrate is taken. Phenolphthalein is used as an indicator and titrated with a calibrated 0.01mol / L NaOH standard solution until it turns slightly red. The end point is that it does not fade for 1min. At the same time, a blank test is performed to analyze the effect of acidity changes on the flavor and shelf life of persimmons. The results are as follows Figure 6 , Figure 7 , Figure 8 shown.

[0048] During the storage process of persimmon cakes, the texture characteristics are an important indicator that affects the taste of persimmon cakes. During the drying process, the skin of persimmon cakes will become hard and the internal flesh will become soft. During the storage process, the texture characteristics will further change. As the degree of deterioration increases, the hardness of the secondary skin formed during drying will gradually decrease. Figure 6The results showed that with the increase of storage days, the hardness of the secondary outer skin formed during the drying of the dried persimmons in each group showed a trend of gradually decreasing, the pectin in the outer skin gradually decomposed, and the hardness became softer and gradually tended to the inner flesh. The hardness of the control group decreased rapidly within 30 days of storage, and the hardness of the vacuum packaging group decreased significantly within 30 days of storage, and then the downward trend gradually became gentle. The hardness of the modified atmosphere packaging group decreased more evenly, indicating that the modified atmosphere has a good effect on maintaining the surface hardness of the dried persimmons, and the modified atmosphere packaging has a good effect in maintaining the hardness of the dried persimmon skin.

[0049] With the influence of persimmon microorganisms, the total acid content of persimmon will continue to increase during storage. The total acid content of persimmon shows a trend of gradually increasing with the extension of storage time. This change may be related to the oxidation, enzymatic reaction or other biochemical pathways of organic acids such as fruit acids in persimmon. Figure 7 The results showed that as the storage days of persimmons increased, the total acid content in the persimmons gradually increased. The total acid content in the control group showed an obvious upward trend at the beginning of storage, indicating that the acidic components in the persimmons were naturally degraded under normal temperature storage, resulting in an increase in acidity. The deoxidizer packaging group showed an obvious upward trend at 40 days, the vacuum packaging group showed an obvious upward trend at 40 days, and the total acid content in the modified atmosphere packaging group was low, with a gentle upward trend and basically flat after 70 days, indicating that the modified atmosphere packaging technology has a good inhibitory effect on the acid production inside the persimmons, and has a significant effect in slowing down the increase in the acidity of the persimmons.

[0050] Dried persimmons will continue to lose water and dry out during storage. Figure 8 The results showed that the moisture content of each group of persimmons decreased continuously during storage. The moisture content of the modified atmosphere packaging group, vacuum packaging group, and deoxidizer packaging group decreased slowly at first, and then the rate of decrease increased. The moisture content of the control group was lost faster than that of the above three groups, and it was significantly reduced after 70 days of storage. After 80 days of storage, the moisture content of the vacuum packaging group and the modified atmosphere packaging group decreased more, indicating that the degree of transpiration deterioration inside the persimmons increased.

[0051] Based on the above experimental results, the present invention adopts modified atmosphere packaging to store dried persimmons.

[0052] 5. Experiment on UV treatment of persimmon

[0053] The dried persimmons with a moisture content of about 40% and not frosted were harvested and grouped, and each group of persimmons was packed into polyethylene plastic bags and sealed. The wavelength was 250nm and the irradiation intensity was 140μW / cm 2, a 60W ultraviolet lamp was placed 1m above the surface of the persimmon cake to irradiate the persimmon cake with ultraviolet light, and the irradiation time was set to 0, 10, 20, 30, and 40 minutes respectively. After the irradiation was completed, the persimmon cake was placed in a constant temperature of 30°C and stored for 7 days, and then taken out to measure the changes in the surface chromaticity values ​​of each group of persimmon cakes. Compared with the persimmon cakes in the control group without ultraviolet irradiation, the chromaticity values ​​of the persimmon cakes showed an upward trend with the increase of ultraviolet treatment time of the persimmon cakes in different groups, indicating that ultraviolet irradiation of unfrost persimmon cakes can maintain the weakened appearance brought by the storage link of persimmon cakes, and ultraviolet irradiation can reduce the occurrence of browning of persimmon cakes by destroying the active center of PPO or inhibiting its synthesis, thereby better protecting the color quality of persimmon cakes. The present invention more effectively prevents the deterioration of persimmon cakes by subjecting the persimmon cakes to ultraviolet irradiation for more than 20 minutes before entering the storage link.

[0054] Example 1

[0055] Step 1: Dried persimmon processing

[0056] Around the Frost Descent solar term, select persimmons, peel them and hang them in a ventilated and cool place. When the moisture content of the persimmons reaches 38% to 43%, the inside of the fruit becomes soft and the outside becomes hard, knead them by hand to make the texture uniform inside and outside, and shape them into spindle-shaped persimmon cakes. Then select persimmon cakes with flat surfaces and no cracks, cut off the fruit stalks and sepals, and use a brush to clean impurities adhering to the surface of the persimmon cakes.

[0057] Step 2: Quickly frost the dried persimmon

[0058] The dried persimmons processed in step 1 are placed in a precooling room at 0-2°C for precooling, and then transferred to a frost removal room for frost removal periodic temperature control. After a period of temperature control timing starts, a cooling operation is first performed to gradually cool the temperature of the frost removal room from -4°C to -12°C, and the cooling time control lasts for about 100 minutes; then the temperature of the frost removal room is gradually raised to -4°C, and the temperature rise control lasts for about 80 minutes, so far one cycle is completed, and the same cycle is 180 minutes in total. The same batch of dried persimmons is continuously cycled for periodic temperature control, and the frosting area on the surface of the dried persimmons is greater than 90% after 16 cycles.

[0059] Step 3: Ozone treatment

[0060] Place dried persimmons with a frosting area greater than 90% in a single polypropylene hard spindle-shaped tray, stack the dried persimmons with the tray on the fence, and transfer them to a circulating ventilation fumigation box. The concentration of ozone gas in the fumigation box is maintained at 30-35 mg / m 3 The fumigation time lasts for 30 minutes, the ambient temperature in the box is maintained at 17±3℃, and the relative humidity is maintained at 55±5%, ensuring that the ozone gas circulates through the purification system air duct during the fumigation period and the ozone gas is evenly distributed between the dried persimmons.

[0061] Step 4: Pack dried persimmons into bags

[0062] The persimmons treated with ozone in step 3 are taken out of the fumigation box, and the persimmons are individually bagged in a sterile operating room, and packaged in a polyethylene / polyamide composite plastic bag with a double-side thickness of 0.16 mm and a length and width of 11 cm×10 cm. 5 g of oxygen absorber wrapped in a non-woven bag (PET / PP / PE material) is placed in the bag, and the mass percentage composition of the oxygen absorber is: 60% iron powder, 5% sodium chloride, 25% calcium carbonate, and 10% sodium bicarbonate.

[0063] Step 5: Modified atmosphere bag sealing

[0064] The bag filled with dried persimmons in step 4 is placed in a modified atmosphere packaging machine for inflation and sealing. The specific method is: first degas for 15 to 20 seconds at a vacuum degree of 90 to 95 kPa to exhaust the air in the bag as much as possible, and then fill it with a mixed gas of carbon dioxide and nitrogen. The volume percentage of the mixed gas is: 85% carbon dioxide and 15% nitrogen. The bag is sealed after the pressure of the mixed gas in the bag reaches 0.08 to 0.09 MPa.

[0065] 6. Ultraviolet radiation

[0066] The air-filled dried persimmons were spread flat in the UV irradiation chamber and irradiated with a UV lamp with a wavelength of 250nm. The UV lamp was 1m away from the surface of the packaging bag and the irradiation intensity was 140μW / cm 2 The irradiation time for each batch of persimmon cakes is 30 minutes.

[0067] Comparative Example 1

[0068] Step 1: Dried persimmon processing

[0069] Around the Frost Descent solar term, select persimmons, peel them and hang them in a ventilated and cool place. When the moisture content of the persimmons reaches 38% to 43%, the inside of the fruit becomes soft and the outside becomes hard, knead them by hand to make the texture uniform inside and outside, and shape them into spindle-shaped persimmon cakes. Then select persimmon cakes with flat surfaces and no cracks, cut off the fruit stalks and sepals, and use a brush to clean impurities adhering to the surface of the persimmon cakes.

[0070] Step 2: Bloom naturally

[0071] Allow the dried persimmons processed in step 1 to frost naturally for 20 days.

[0072] Step 3: Ozone treatment

[0073] Place the dried persimmons after frost removal in step 2 in a single polypropylene hard spindle-shaped tray, stack the dried persimmons with the tray on the fence, and transfer them to a circulating ventilation fumigation box. The concentration of ozone gas in the fumigation box is maintained at 30-35 mg / m 3The fumigation time lasts for 30 minutes, the ambient temperature in the box is maintained at 17±3℃, and the relative humidity is maintained at 55±5%, ensuring that the ozone gas circulates through the purification system air duct during the fumigation period and the ozone gas is evenly distributed between the dried persimmons.

[0074] Step 4: Pack dried persimmons into bags

[0075] The persimmons treated with ozone in step 3 were taken out of the fumigation box, and the persimmons were individually bagged and sealed in a sterile operating room using polyethylene / polyamide composite plastic bags with a double-side thickness of 0.16 mm and a length and width of 11 cm×10 cm.

[0076] The dried persimmon products processed and preserved by the methods of Example 1 and Comparative Example 1 were stored at room temperature for 90 days and then their physical and chemical indicators were tested. The results are shown in Tables 1 and Figures 10-11 .

[0077] Table 1 Physical and chemical indicators of dried persimmons obtained by different processing methods after storage for 90 days

[0078] Serial number Element Example 1 Comparative Example 1 1 Mass(g) 45.23 43.75 2 Moisture content (%) 40.72 38.73 3 <![CDATA[Total number of colonies (log 10 CFU / g)]]> 0.93 1.70 4 <![CDATA[Total number of molds (log 10 CFU / g)]]> 2.64 3.80 5 Total acid content (g / 100g) 1.75 2.71 6 Skin hardness (N) 177.57 40.71 7 Surface chromaticity value (L) 31.92 21.11 8 Persimmon frost area (%) 93 35 9 Total sugar content (g / 100g) 61.34 57.69

[0079] Depend on Fig.10 , 11 It can be seen that the frost area of ​​the dried persimmon product processed and preserved by the method of Example 1 is significantly larger than that of the method of Comparative Example 1, and the frost time is short (only 2 days for Example 1, 20 days for Comparative Example 1). As can be seen from Table 1, after 90 days of storage, the physical and chemical indicators of the dried persimmon product processed and preserved by the method of Example 1 are also better than those of Comparative Example 1.

Claims

1. A method for preserving dried persimmons for accelerating frost removal and prolonging storage period, characterized in that: The steps include: Step 1: Dried persimmon processing Around the Frost Descent solar term, select persimmons, peel them and hang them in a ventilated and cool place. When the moisture content of the persimmons reaches 38% to 43%, the inside of the fruit becomes soft and the outside becomes hard, knead them manually to make the texture uniform inside and outside, and shape them into spindle-shaped persimmons. Then select persimmons with a flat surface and no cracks, cut off the fruit stalks and sepals, and use a brush to clean the impurities adhering to the surface of the persimmons. Step 2: Quickly frost the dried persimmon The dried persimmons processed in step 1 are placed in a precooling room at 0 to 2°C for precooling, and then transferred to a frost removal room for temperature control of the frost removal cycle of the dried persimmons; the temperature control method is as follows: the temperature of the frost removal room is gradually cooled from -5 to -3°C to -13 to -11°C, and the cooling time is controlled to last for 90 to 100 minutes; then the temperature of the frost removal room is gradually heated to -5 to -3°C, and the heating time is controlled to last for 80 to 90 minutes, so that one cycle ends, and the same cycle is 170 to 190 minutes in total; for the same batch of dried persimmons, the temperature control is continuously cycled for more than 16 cycles until the frosting area on the surface of the dried persimmons is greater than 90%; Step 3: Ozone treatment The dried persimmons with a surface frosting area greater than 90% obtained in step 2 are placed in a single polypropylene hard spindle-shaped tray, the dried persimmons with the tray are stacked on the fence, and transferred to a circulating ventilation fumigation box, and the concentration of ozone gas in the fumigation box is maintained at 30-35 mg / m 3 The fumigation time lasts for 30 to 40 minutes, the ambient temperature in the box is maintained at 17±3℃, and the relative humidity is maintained at 55±5%, ensuring that the ozone gas circulates through the purification system air duct during the fumigation period and the ozone gas is evenly distributed between the dried persimmons; Step 4: Pack dried persimmons into bags The dried persimmons treated with ozone in step 3 are taken out of the fumigation box, and the dried persimmons are individually bagged in a sterile operation room, and an oxygen absorber wrapped in a non-woven bag is placed in the packaging bag; Step 5: Modified atmosphere bag sealing The packaging bag filled with dried persimmon in step 4 is placed in a modified atmosphere packaging machine, first degassed for 15 to 20 seconds at a vacuum degree of 90 to 95 kPa to exhaust the air in the bag, and then filled with a mixed gas of carbon dioxide and nitrogen, wherein the volume percentage of the mixed gas is: 80% to 90% carbon dioxide and 10% to 20% nitrogen, and the bag is sealed after the pressure of the mixed gas in the bag reaches 0.08 to 0.09 MPa; Step 6: UV exposure Spread the dried persimmons packed in the air bag in step 5 in the UV irradiation chamber and irradiate them with a UV lamp with a wavelength of 240-280 nm. The UV lamp is 0.8-1.2 m away from the surface of the packaging bag and the irradiation intensity is 140-160 μW / cm 2 The irradiation time is 20 to 40 minutes.

2. The method for preserving dried persimmons for accelerating frost removal and extending storage period according to claim 1, characterized in that: In step 2, the variable temperature control method is: gradually cool down the temperature of the frost outlet room from -4°C to -12°C, and control the cooling time to last for 90 to 100 minutes; then gradually increase the temperature of the frost outlet room to -4°C, and control the heating time to last for 80 to 90 minutes. This is the end of one cycle, and the same cycle is 180 minutes in total.

3. The method for preserving dried persimmons for accelerating frost removal and extending storage period according to claim 1, characterized in that: In step 3, the fumigation time lasts for 30 minutes.

4. The method for preserving dried persimmons for accelerating frost removal and extending storage period according to claim 1, characterized in that: In step 4, the dried persimmons are packaged in a polyethylene / polyamide composite plastic bag with a double-side thickness of 0.16 to 0.20 mm and a side length of 10 to 12 cm.

5. The method for preserving dried persimmons for accelerating frost removal and extending storage period according to claim 1, characterized in that: In step 4, the oxygen absorber comprises the following components in mass percentage: 55% to 65% iron powder, 5% to 10% activated carbon, 15% to 25% calcium carbonate, and 5% to 10% sodium bicarbonate.

6. The method for preserving dried persimmons for accelerating frost removal and extending storage period according to claim 1, characterized in that: In step 5, the volume percentage composition of the mixed gas is: 85% carbon dioxide and 15% nitrogen.

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