Desertification-free cold storage low-temperature after-ripening method for plum-leaf crab seeds

Abstract

The invention discloses a low-temperature after-ripening method for malus spectabilis seeds in a desertification-free refrigeration house, and relates to the field of low-temperature after-ripening method.The low-temperature after-ripening method comprises the following steps that S1, multi-dimensional fruit grading and targeted repairing are conducted, directional pretreatment and targeted repair are carried out on fruits with different maturity degrees and damage grades; s2, adaptive stepped pre-cooling: according to the maturity and damage grade of the fruits, different pre-cooling strategies are adapted; s3, performing zoning and layering temperature-changing after-ripening; and S4, carrying out integrated connection treatment. According to the method, fruit maturity and micro-damage grading is completed within 2 h after harvesting, directional pretreatment and targeted repair are matched, the situation that dormancy of low-maturity fruits is not thoroughly removed is avoided, the hidden danger of mold breeding caused by damaged fruits is eliminated, meanwhile, by combining after-ripening environment humidity and gas concentration regulation and control, reproduction of penicillium and fusarium is reduced, the seed mildew rate is reduced, and the seed quality is improved. The after-ripening uniformity of various fruits is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of low-temperature after-ripening method, in particular to a low-temperature after-ripening method for seed of Malus micromalus without sand in cold storage. BACKGROUND

[0002] After the seed of Malus micromalus is picked, it must go through a physiological after-ripening stage to break dormancy and then can germinate normally. The most common after-ripening method in the industry is the wet sand layering method. This method provides stable temperature and humidity for the seed by wet sand, helps the seed embryo to develop, and also allows the inhibiting germination substances in the seed to decrease and the promoting germination substances to increase, so as to ultimately achieve the breaking of seed dormancy.

[0003] The existing wet sand layering method has many difficult-to-solve problems in actual use. Firstly, it ignores the influence of the difference in maturity and surface micro-damage of the picked Malus micromalus. All fruits, regardless of the degree of coloring and soluble solids content (maturity index) and whether there are scratches or depressions (micro-damage) on the surface, are directly mixed for sand layering treatment. Neither targeted pretreatment is done for fruits of different maturity, nor targeted repair is done for damaged parts. In this way, fruits of low maturity take longer to after-ripen and break dormancy incompletely in the same sand layer environment due to insufficient physiological state in the early stage. Fruits with surface damage become a breakthrough for mold breeding in the high-humidity environment of wet sand, further aggravating the subsequent moldy problem.

[0004] Moreover, it requires a large amount of wet sand, with a volume of 5 times that of the seed, and occupies a lot of space. For every 10 tons of Malus micromalus, 200 square meters of space is needed, resulting in serious waste of space resources. If the sand layer is stacked more than 2 layers, it will be compacted due to gravity, and the seed around it will lack oxygen. At most, 200 kg of seeds can be stacked per square meter, and the efficiency is very low when large-scale processing is performed. This method takes a long time to after-ripen, usually more than 40 days. In winter, the temperature fluctuates greatly, and the temperature distribution in the sand layer is uneven. In addition, the problems of maturity and damage are superimposed, resulting in greater differences in seed after-ripening degree. Finally, it leads to substandard seed germination rate, which cannot meet the demand for stable seedling emergence in large-scale seedling raising. Moreover, the high water content of wet sand itself is prone to the breeding of molds such as penicillium and fusarium. These molds will start to grow within 4 hours, and with the help of damaged fruits, the seed moldy rate is even higher. SUMMARY

[0005] The present application aims to provide a low-temperature after-ripening method for seed of Malus micromalus without sand in cold storage to solve the problems in the background art.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solution: a low-temperature after-ripening method for seed of Malus micromalus without sand in cold storage, comprising the following steps:

[0007] S1, multi-dimensional fruit grading and targeted repair: within 2h after harvest, the postharvest fruits are sequentially subjected to maturity grading and micro-damage grading, and the fruits of different maturity and damage grades are subjected to directional pretreatment and targeted repair;

[0008] S2, adaptive stepwise precooling: different precooling strategies are adapted according to the maturity and damage grade of the fruits;

[0009] S3, zoned and layered variable-temperature after-ripening: the pre-cooled fruits are zoned according to the damage condition and are placed in an after-ripening cold storage in a standardized V-shaped stack; based on the monitoring of the temperature, humidity and gas concentration in different functional zones of the cold storage and different depths of the fruit stack, the temperature, O2 and CO2 concentration of the after-ripening section are dynamically adjusted, and the local temperature and humidity are simultaneously compensated and controlled until the seed embryo moisture is simultaneously reduced to the target range;

[0010] S4, integrated and connected processing: after the after-ripening is completed, gradient warming, flexible mechanical separation and low-temperature acclimation are performed, and the seeds directly enter the germination or short-term storage state.

[0011] Preferably, the specific standards and directional pretreatment methods of the maturity grading in step S1 are as follows:

[0012] S111, maturity grading: the soluble solid content is obtained by near-infrared spectroscopy full-fruit scanning, and the L* value of the skin surface color difference is simultaneously collected, a two-dimensional judgment space is constructed, a dynamic threshold band is set in the judgment space, the fruits are divided into two grades of half-ripe fruits and fully ripe fruits, and an overlapping buffer band is reserved between the two grades; after the grading is completed, the maturity identity code of each fruit is automatically assigned by the system, and the subsequent directional pretreatment path is triggered accordingly;

[0013] S112, directional pretreatment: half-ripe fruit path: the half-ripe fruits are placed in a vacuum-atmospheric pressure cyclic immersion device, and a low-concentration chitosan functional solution is subjected to negative pressure penetration-atmospheric pressure uniform coating to form an edible antibacterial film on the fruit surface; fully ripe fruit path: a micron-sized atomization device is used to uniformly spray a vitamin C functional solution on the fruit surface.

[0014] Preferably, the detection method of the micro-damage grading in step S1 is as follows:

[0015] S121, high-resolution backlight imaging acquisition: an industrial camera is used in cooperation with an adjustable LED backlight panel to perform 360° rolling shooting on a single fruit, and a shadow-free, high-contrast original image is obtained;

[0016] S122, micro-damage feature extraction and quantification: the original image is converted into a grayscale image, a full-fruit grayscale histogram is established, the dark area with a grayscale value ≤(G0-15%) and an area ≥0.1mm² is automatically marked as a suspected damage based on the normal skin grayscale mean value G0, the suspected damage area ratio and the maximum Feret diameter are simultaneously calculated, and a damage index DI is generated.

[0017] S123, tertiary classification standard: no damage fruit: DI = 0, uniform gray scale on fruit surface, no scratches, no depression; slightly damaged fruit: 0 < DI < 5%, and the maximum scratch width is ≤0.5mm or the depression area is <1cm²; severely damaged fruit: 5%≤DI≤10%, and the scratch width is >0.5mm but ≤2mm or the depression area is 1cm²-3cm²;

[0018] S124, automatic diversion and marking: the visual system triggers a high-speed air jet sorting mechanism to divert the fruit to the corresponding processing channel and gives the damaged fruit an identity code corresponding to the damage level every time it detects a slightly or severely damaged fruit.

[0019] Preferably, the targeted repair method of micro-damage in step S1 is as follows:

[0020] Slightly damaged fruit: a 0.03% chitosan-nano silver composite solution is sprayed on the damaged area, the spraying amount is 0.5-1mL / cm² of the damaged area, and a transparent protective film is formed after standing for 5min;

[0021] Severely damaged fruit: the damaged area is treated with low-temperature plasma, and the damaged surface residues are wiped off with a sterile dry cloth after treatment.

[0022] Preferably, the adaptive precooling based on maturity and damage level in step S2 includes the following steps:

[0023] S21, in the same precooling cavity, the differentiated precooling temperature range, duration and cooling air speed are matched in real time according to the interactive classification results of fruit maturity and surface damage degree, and the core temperature ≤2℃ is taken as the unified endpoint determination index;

[0024] S22, when the single precooling fails to reach the endpoint, the system automatically prolongs the precooling time and retests until the core temperature meets the requirement of ≤2℃.

[0025] Preferably, the cold storage partitioning and local temperature and humidity compensation method in step S3 is as follows:

[0026] S311, cold storage partitioning: the post-ripening cold storage is divided into three functional zones, evaporator zone, middle zone and corner zone, and three temperature and humidity monitoring points are uniformly arranged in each zone;

[0027] S312, local compensation control: when the temperature in the evaporator zone is ≤-0.5℃, the built-in 500W electric heating wire in the zone is started to adjust the temperature back to 0-0.5℃; when the humidity in the corner zone is ≤62%, the built-in ultrasonic humidifier in the zone is started to increase the humidity to 68-70%; after compensation control, the temperature deviation of the three functional zones should be ≤±0.3℃ and the humidity deviation should be ≤±2%.

[0028] Preferably, the dynamic parameter adjustment logic based on real-time monitoring of seed embryo moisture in step S3 is as follows:

[0029] S321, Seed embryo moisture monitoring: Random sampling every 12 hours during the after-ripening period, and measuring seed embryo moisture by low-temperature freeze-drying method;

[0030] S322, Stage-based parameter adjustment: moisture reduction stage: keep the library temperature at 0-1°C, while increasing O2 and decreasing CO2 to accelerate water discharge; moisture transition stage: lower the library temperature to -0.5-0.5°C, while decreasing O2 and increasing CO2 to slow down the water loss rate; moisture standard stage: return the library temperature to 0-1°C, while increasing O2 and decreasing CO2 to stabilize the seed embryo moisture in the target interval;

[0031] S323, Dormancy release verification: after the seed embryo moisture reaches the target interval, measure the endogenous gibberellin and abscisic acid content, and only when the gibberellin is ≥1.8 times the initial value and the abscisic acid is ≤58% of the initial value, the low-temperature after-ripening is ended.

[0032] Preferably, in the stage-based parameter adjustment process, a predictive feedback method based on the rate of change of seed embryo moisture is also included, comprising the following steps:

[0033] S331, Real-time rate calculation: based on the starting point of after-ripening, sample rolling at fixed time intervals, establish a seed embryo moisture decay curve, and calculate the average moisture change rate V in the current period;

[0034] S332, Rate and threshold double limit judgment: the system has built-in variable threshold group {Vmin, Vmax} matched with the stage, which are used to identify after-ripening delay and dehydration stress, respectively;

[0035] S333, Predictive fine-tuning of gas parameters: when V>Vmax, dehydration stress is determined, immediately lower the O2 volume fraction, increase the CO2 volume fraction, and appropriately lower the after-ripening temperature to inhibit the respiratory intensity; when V

[0036] S334, Dynamic target threshold drift: during the moisture transition stage, if V is lower than Vmin for a long time, the system will automatically raise the starting moisture threshold of the subsequent moisture standard stage;

[0037] S335, Closed-loop verification: after each gas fine-tuning, continue to monitor the V value in the subsequent period, if V still exceeds the threshold band, repeat the fine-tuning until V returns to the safe interval, to ensure that the seed embryo moisture decays smoothly along the set trajectory, and the low-temperature after-ripening is ended when the two indicators of endogenous hormones meet the requirements.

[0038] Preferably, the standardization stacking in step S3 is a V-shaped structure with a bottom layer width of 1.2 m, a top layer width of 0.6 m, a stack height of 0.8 m, an interlayer gap of 3 cm, and an adjacent stack spacing of 0.5 m.

[0039] Preferably, in step S3, the gas flows along the V-shaped stacking slope by setting the side air outlets on both sides of the cold storage and the return air valve at the top; and CO2 sensors are arranged at different depths in the stack, and when the monitored CO2 concentration is greater than or equal to 2%, the corresponding area side air speed and air exchange frequency are automatically increased.

[0040] The technical effects and advantages of the present application are as follows:

[0041] (1) The present application classifies the maturity (coloring degree, soluble solids content) and micro-damage (scratches, depressions) of fruits within 2 hours after harvest, and combines directional pretreatment and targeted repair, which not only avoids incomplete dormancy release of fruits with low maturity, but also eliminates the hidden danger of mold breeding caused by damaged fruits, and at the same time, combines with the humidity and gas concentration control of the post-ripening environment, reduces the reproduction of penicillium and fusarium, reduces the seed rot rate, and improves the uniformity of post-ripening of various fruits.

[0042] (2) The present application uses a sand-free cold storage low-temperature ripening method, which does not require solid substrates such as wet sand, thereby saving 5 times the volume of wet sand consumed in the existing method and greatly reducing the site occupation; at the same time, it breaks through the limitation of sand layer stacking, improves the processing capacity per unit site through standardized stacking and partition control, reduces the intensity of manual operation, and adapts to large-scale processing needs.

[0043] (3) The present application uses an adaptive step precooling and partitioned-laminated variable temperature ripening process to break through the limitation of the existing wet sand layer accumulation method with a ripening period of more than 40 days, to quickly promote seed dormancy release, so that the seed enters the germination or seedling stage more quickly, and to improve the overall production efficiency of malus fruit seedling production.

[0044] (4) The present application uses multi-dimensional control of graded repair and dynamic environment compensation to solve the problems of uneven ripening and substandard seedling emergence rate caused by temperature fluctuations and fruit differences in the existing method, effectively improves the seedling emergence rate, reduces the difference in seedling emergence between batches, and meets the requirements of large-scale seedling production for seed germination stability. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The present application is a schematic block diagram of the ripening method. DETAILED DESCRIPTION

[0046] With reference to the accompanying drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the protection scope of the present application.

[0047] The present application provides a low-temperature post-maturation method for Malus micromalus seed in a sand-free cold storage, as shown in the following steps: Figure 1 The present application provides a low-temperature post-maturation method for Malus micromalus seed in a sand-free cold storage, as shown in the following steps:

[0048] S1, multi-dimensional fruit grading and targeted repair: the postharvest fruits are sequentially subjected to maturity grading and micro-damage grading within 2h, and the fruits of different maturity and damage grades are subjected to directional pretreatment and targeted repair;

[0049] S2, adaptive stepwise precooling: different precooling strategies are adapted according to the maturity and damage grade of the fruits;

[0050] S3, zoned and layered variable-temperature post-maturation: the pre-cooled fruits are zoned according to the damage and placed in the post-maturation cold storage in a standardized V-shaped stack; based on the monitoring of the temperature, humidity and gas concentration in different functional zones of the cold storage and different depths of the fruit stack, the temperature, O2 and CO2 concentration of the post-maturation section are dynamically adjusted, and the local temperature and humidity are compensated and controlled until the seed embryo moisture is simultaneously reduced to the target range;

[0051] S4, integrated connection processing: after the post-maturation, gradient warming, flexible mechanical separation and low-temperature acclimation are performed, and the seed directly enters the germination or short-term storage state.

[0052] By sequentially performing the multi-dimensional fruit grading and targeted repair, the adaptive stepwise precooling, the zoned and layered variable-temperature post-maturation, and the integrated connection processing, the problems of uneven post-maturation caused by no fruit grading and repair, substandard fruit core temperature caused by single precooling parameter, local condition imbalance caused by no zoned regulation of post-maturation environment, and poor connection of post-processing are solved, the sand-free low-temperature post-maturation of Malus micromalus seed is realized, the seed embryo moisture can be stably reduced to the target range, the seed can directly enter the germination or short-term storage without secondary low-temperature or wet sand layering, and meanwhile the uniformity and efficiency of the post-maturation process are improved, and the moldy risk is reduced.

[0053] In step S1, the specific standards of maturity grading and the directional pretreatment method are as follows:

[0054] S111, maturity grading: obtain the soluble solids content by near-infrared spectroscopy full-fruit scanning, and simultaneously collect the fruit skin surface color difference L* value, construct a two-dimensional judgment space, half-ripe fruit: soluble solids content is 8-10 Brix, L* value is 60-65; ripe fruit: soluble solids content is 11-13 Brix, L* value is 50-55; set a dynamic threshold band in the judgment space, divide the fruit into two levels of half-ripe fruit and ripe fruit, and reserve an overlapping buffer zone between the two levels to prevent marginal misjudgment; after grading, the system automatically assigns a maturity identity code to each fruit, and triggers the subsequent directional pretreatment path accordingly;

[0055] S112, directional pretreatment: half-ripe fruit path: place the half-ripe fruit in a vacuum-normal pressure cyclic immersion device, and use a low-concentration chitosan functional solution to perform negative pressure penetration-normal pressure uniform coating on the fruit surface, forming an edible antibacterial film on the fruit surface, reducing the risk of membrane lipid peroxidation in the subsequent low-temperature stage; ripe fruit path: use a micron-sized atomizing device to uniformly spray a vitamin C functional solution on the fruit surface, quickly neutralize free radicals, inhibit fruit skin browning and cell membrane degradation, and maintain the balance of reactive oxygen species during low-temperature ripening.

[0056] By using the maturity grading standard of near-infrared spectroscopy detection of soluble solids (SSC) combined with fruit skin color difference (L* value), and the directional pretreatment method of chitosan solution soaking for half-ripe fruit and vitamin C solution spraying for ripe fruit, the problem of different maturity fruits not being adapted to subsequent processing due to not distinguishing fruit maturity in the existing ripening process is solved, and accurate pretreatment of different maturity malus micromalus fruits is achieved. The half-ripe fruit can enhance the permeability of the fruit skin to promote the transformation of endogenous hormones, and the ripe fruit can inhibit the oxidative browning of the fruit skin, laying a uniform physiological foundation for subsequent stepwise precooling and variable-temperature ripening, and improving the overall ripening consistency.

[0057] In step S1, the detection method of micro-damage grading is as follows:

[0058] S121, high-resolution backlit imaging acquisition: use an industrial camera combined with an adjustable LED back light panel to perform 360° rolling shooting on a single fruit, and obtain a shadow-free, high-contrast original image;

[0059] S122, micro-damage feature extraction and quantification: convert the original image into a grayscale image, and establish a full-fruit grayscale histogram; take the normal fruit skin grayscale mean value G0 as the reference, and automatically mark the dark area with a grayscale value of ≤(G0-15%) and an area of ≥0.1 mm² as a suspected damage; simultaneously calculate the suspected damage area ratio and the maximum Feret diameter, and generate a damage index DI;

[0060] S123, third-level grading standard: no damage fruit: DI = 0, fruit surface gray uniformity, no scratches, depressions; slightly damaged fruit: 0 < DI < 5%, and the maximum scratch width is ≤0.5mm or the depression area is <1cm²; severely damaged fruit: 5%≤DI≤10%, and the scratch width is >0.5mm but ≤2mm or the depression area is 1cm²-3cm²;

[0061] S124, automatic diversion and marking: the vision system triggers a high-speed air jet sorting mechanism every time it detects a slightly or severely damaged fruit, diverting the fruit to the corresponding processing channel and giving it a damage level identity code for subsequent dynamic matching of differentiated pre-cooling and ripening parameters, achieving accurate, non-destructive and efficient micro-damage grading of crabapple seeds.

[0062] By using a high-resolution machine vision combined with backlit imaging detection method and grading according to the grading standards of no damage fruit, slightly damaged fruit and severely damaged fruit, the problem of mixing damaged fruits into the whole process due to the inability to accurately identify fruit micro-damage in the existing ripening process is solved, the rapid and accurate differentiation of crabapple fruit surface micro-damage is achieved, the fruit categories of different damage levels are clearly defined, providing clear processing basis for subsequent targeted repair, and avoiding the impact of damaged fruits on the overall ripening quality due to unrecognized damaged fruits.

[0063] In step S1, the targeted repair method of micro-damage is as follows:

[0064] Slightly damaged fruit: 0.03% chitosan-nano silver composite solution (nano silver concentration is 50ppm) is sprayed on the damaged area, the spraying amount is 0.5-1mL / cm² of damaged area, and a transparent protective film is formed after standing for 5min;

[0065] Severely damaged fruit: low-temperature plasma is used to treat the damaged area, the treatment parameters are power 80W, treatment time 30s, and treatment temperature 5-8℃, and sterile dry cloth is used to wipe the residual substances on the damaged surface after treatment.

[0066] By using chitosan-nano silver composite solution spraying for slightly damaged fruit and low-temperature plasma treatment for severely damaged fruit, the problem of mold growth at the damaged site and further spread to affect the surrounding fruits due to un-repaired fruit micro-damage in the existing ripening process is solved, the targeted repair of fruits of different damage levels is achieved, the protective film can be formed on the slightly damaged fruit by the composite solution, and the surface of the severely damaged fruit can be sterilized by low-temperature plasma (the gas is partially ionized to form a mixed system containing electrons, ions and neutral particles, and the overall temperature is maintained in the low-temperature range without damaging the fruit), effectively reducing the mold breeding points at the damaged site and reducing the risk of mold during the overall ripening process.

[0067] Wherein, the precooling based on maturity and damage grade in step S2 comprises the following steps:

[0068] S21, for semi-mature fruits: no damage fruits: precooling temperature -4℃ to -1℃, duration 7h, cooling section wind speed 1.8m·s-1; slightly damaged fruits: precooling temperature -3℃ to -1℃, duration 6.5h, cooling section wind speed 1.6m·s-1; severely damaged fruits: precooling temperature -5℃ to -2℃, duration 5.5h, cooling section wind speed 2.0m·s-1; for fully mature fruits: no damage fruits: precooling temperature -6℃ to -2℃, duration 5h, cooling section wind speed 1.8m·s-1; slightly damaged fruits: precooling temperature -5℃ to -2℃, duration 5.5h, cooling section wind speed 1.6m·s-1; severely damaged fruits: precooling temperature -7℃ to -3℃, duration 4.5h, cooling section wind speed 2.0m·s-1;

[0069] S22, precooling end point determination: the core temperature is determined by inserting a temperature probe, if the core temperature >2℃, then the precooling is automatically extended for 0.5h and retested until the core temperature ≤2℃, ensuring that the Malus hallings apple seeds enter the uniform and controllable low temperature safety core temperature before the non-sandification post-ripening stage.

[0070] By constructing the precooling parameters based on fruit maturity and damage grade (defining the precooling temperature range, duration and wind speed corresponding to different types of fruits), the problem of physiological damage of fruits caused by the single precooling parameter in the existing post-ripening process is solved, the precise precooling control of Malus hallings fruits with different maturity-damage grades is realized, and the core temperature of all types of fruits can be stably controlled to ≤2℃ after precooling, providing a prerequisite for the uniform post-ripening of subsequent temperature change.

[0071] Wherein, the cold storage partition and local temperature and humidity compensation method in step S3 are as follows:

[0072] S311, cold storage partition: the post-ripening cold storage is divided into three functional zones, evaporator zone (zone 1, close to the refrigeration evaporator), middle zone (zone 2, geometric center area of the cold storage), corner zone (zone 3, four corners and edge area of the cold storage), and three temperature and humidity monitoring points (temperature detection accuracy ±0.1℃, humidity detection accuracy ±1%) are uniformly arranged in each zone;

[0073] S312, local compensation regulation: when the evaporator area temperature is less than or equal to -0.5℃ (lower than the lower limit of the post-maturation basic temperature), start the 500W electric heating wire built-in (intermittent work, 30s each time, 60s stop), and the temperature is adjusted to 0-0.5℃; when the humidity of the corner area is less than or equal to 62% (lower than the lower limit of the post-maturation humidity), start the ultrasonic humidifier built-in (mist amount 50mL / h) in the area, and the humidity is increased to 68-70%; after compensation regulation, the temperature deviation of the three functional areas should be less than or equal to ±0.3℃, and the humidity deviation should be less than or equal to ±2%.

[0074] By dividing the post-maturation cold storage into an evaporator area, a middle area and a corner area, and setting temperature and humidity monitoring points in each area and corresponding local compensation regulation measures, the problem of inconsistent post-maturation process of fruits caused by large temperature and humidity differences in different areas of the existing post-maturation cold storage is solved, and stable control of temperature and humidity in each functional area of the post-maturation cold storage is achieved, so that the temperature deviation and humidity deviation in each area are controlled within a reasonable range, and fruits in different areas can be in a consistent post-maturation environment, improving the uniformity of post-maturation.

[0075] In step S3, the dynamic parameter adjustment logic based on real-time monitoring of seed embryo moisture is as follows:

[0076] S321, seed embryo moisture monitoring: during post-maturation, 30 fruits are randomly taken from each functional area and each pile depth every 12h, and the low-temperature freeze-drying method is used to measure the seed embryo moisture (detection error ≤0.5%);

[0077] S322, phased parameter adjustment: water content reduction stage (seed embryo initial moisture 25-28%→20%): post-maturation temperature is maintained at 0-1℃, O2concentration is 20-21%, CO2concentration is 1.0-1.5%, and seed embryo moisture metabolism is accelerated; water content transition stage (20%→15%): post-maturation temperature is reduced to -0.5~0.5℃, O2concentration is 18-19%, CO2concentration is 1.5-2.0%, and metabolic rate is slowed down to avoid rapid water content reduction; water content standard stage (15%→target range 12-17% / 5-7%): post-maturation temperature is increased to 0-1℃, O2concentration is 19-20%, CO2concentration is <1.0%, and seed embryo moisture is stabilized;

[0078] S323, dormancy release verification: after the seed embryo moisture reaches the standard, the endogenous gibberellin content (≥1.8 times the initial value) and the abscisic acid content (≤58% of the initial value) are detected, and the post-maturation is terminated only when both indicators reach the standard.

[0079] By dividing the decline, transition, and standard three stages according to the change of seed embryo moisture, and matching the corresponding post-maturation temperature, oxygen and carbon dioxide concentration parameters for each stage, while detecting the endogenous gibberellin and abscisic acid content after the seed embryo moisture reaches the standard, the problem of inaccurate seed embryo moisture control and incomplete dormancy release caused by fixed post-maturation process parameters is solved, realizing accurate post-maturation regulation based on the dynamic change of seed embryo moisture, ensuring that the seed embryo moisture can stably decrease to the target range, and the endogenous hormone level meets the dormancy release requirement, providing physiological guarantee for subsequent seed germination

[0080] In the process of adjusting parameters in stages, a predictive feedback method based on the rate of change of seed embryo moisture is further included, comprising the following steps:

[0081] S331, rate real-time operation: taking the post-maturation starting point as T0, taking samples every 12 hours, establishing a seed embryo moisture decay curve in time sequence, and calculating the current 12h sliding average moisture change rate V (% / h);

[0082] S332, rate and threshold double limit judgment: the system is built-in with a variable threshold group {V_min, V_max} matched with the stage, wherein V_min is used to identify post-maturation delay, and V_max is used to identify dehydration stress;

[0083] S333, predictive fine-tuning of gas parameters: when V>V_max, it is determined that the dehydration is excessive, and the current O2 volume fraction is immediately lowered by 0.3%-0.7%, the CO2 volume fraction is immediately raised by 0.1%-0.3%, and the post-maturation temperature is immediately lowered by 0.2℃-0.5℃ at the same time, so as to inhibit the respiratory burst; when V

[0084] S334, dynamic target threshold drift: in the moisture transition stage, if V is continuously lower than V_min for 36 hours, the system will automatically raise the starting moisture threshold of the subsequent moisture standard stage by 0.5%-1.5% from the preset value, to prevent the overall post-maturation period from being prolonged too much;

[0085] S335, closed-loop verification: after each gas fine-tuning, continue to monitor the V value in the next 12 hours, if V still exceeds the threshold band, repeat the fine-tuning until V returns to the safe interval, to ensure that the seed embryo moisture decays smoothly along the set trajectory, and the post-maturation is ended on time when the gibberellin and abscisic acid double indicators reach the standard.

[0086] In step S3, the stacking design parameters are as follows: the thickness of the customized plastic partition is 5 mm, the aperture is 2 mm, the stacking body is in V-shaped structure, the width of the bottom layer is set to 1.2 m, the width of the top layer is set to 0.6 m, the height of the stacking body is set to 0.8 m, the interlayer gap is set to 3 cm (with an error of ≤0.5 cm), the distance between adjacent stacking bodies is set to 0.5 m (reserved for air duct), and the stacking area of 10 t of fruits is ≤3.5 m².

[0087] Specifically, in step S3, the gas-moisture linkage regulation in the stack is as follows:

[0088] Gas circulation: side air outlets are arranged on both sides of the cold storage (with a wind speed of 1.2-1.5 m・s⁻¹), and a return air valve is arranged at the top. The gas flows along the inclined surface of the V-shaped stack from the bottom layer to the top layer and from the outside to the inside of the stack.

[0089] In-stack monitoring: one micro CO2 sensor (with an accuracy of ±0.05%) is arranged at each of the depths of 0.2 m, 0.5 m and 0.8 m of the stacking body to monitor the CO2 concentration in the stack in real time.

[0090] Abnormal regulation: when the CO2 concentration at a certain depth is ≥2%, the side air speed of the corresponding area is increased to 1.4-1.6 m・s⁻¹, and the air exchange frequency of the return air valve at the top is increased from 1 time / h to 1.5 times / h. If the water loss rate of the embryo at this depth is 10% slower than that outside the stack, dry air with a temperature of 5-8 ℃ and a relative humidity of 50% is mixed into the side air to accelerate the local water loss.

[0091] By using the standardized V-shaped stacking (defining the size of the stacking body, the interlayer gap and the distance between the stacks), and constructing the gas directional circulation and abnormal regulation system in the stack (such as monitoring the CO2 concentration in the stack and adjusting the air speed, mixing dry air), the problem of uneven interlayer gap between the existing fruit stacks leading to dead angles of gas circulation in the stack, water stratification and affecting the consistency of after-ripening is solved. The smooth circulation of gas and uniform distribution of water in the stack are realized, the local accumulation of CO2 or abnormal water in the stack is avoided, and the consistency of the after-ripening process of fruits at different depths in the stack is ensured, while the site utilization rate is improved.

[0092] In step S4, the specific operation of gradient heating is as follows: 2 h before the end of after-ripening, the heating program is started, the temperature of the cold storage is increased from the after-ripening temperature to 3-5 ℃ at a rate of 1 ℃ / h, and the separated seeds are immediately sent to a temporary storage bin with a temperature of 5-8 ℃. The temporary storage time is set to ≤1 h to avoid the formation of condensed water on the surface of the fruits.

[0093] Finally, it should be noted that the above is only the preferred embodiment of the present application, and is not intended to limit the present application, although the foregoing embodiments of the present application are described in detail, for those skilled in the art, it still can be modified to the technical solution recorded in the foregoing embodiments, or equivalent replacement of some technical features, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application, should be included in the protection scope of the present application.

Claims

1. A method for low-temperature post-ripening of crabapple seeds in a sand-free cold storage, characterized in that, It includes the following steps: S1. Multi-dimensional fruit grading and targeted repair: After harvesting, fruits are successively graded by maturity and micro-damage within a certain period of time, and targeted pretreatment and repair are carried out for fruits with different maturity and damage levels; S2. Adaptive stepped precooling: According to the maturity and damage level of fruits, different precooling strategies are adapted; S3. Zoned and layered variable-temperature ripening: The precooled fruits are zoned according to the damage situation and placed in a ripening cold storage by using standardized V-shaped stacking; Based on the monitoring of temperature, humidity and gas concentration in different functional areas of the cold storage and at different depths inside the fruit stack, the temperature, O2 and CO2 concentrations in the ripening stage are dynamically adjusted, and the local temperature and humidity are compensated and regulated until the moisture of the seed embryo synchronously drops to the target range; S4. Integrated connection processing: After ripening, gradient heating, flexible mechanical separation and low-temperature acclimation are carried out, and the seeds directly enter the germination or short-term storage state.

2. The method for low-temperature post-ripening of crabapple seeds in a sand-free cold storage according to claim 1, characterized in that, The specific criteria for the maturity grading and the method of targeted pretreatment described in step S1 are as follows: S111. Maturity grading: The soluble solid content is obtained by full-fruit scanning with near-infrared spectroscopy, and the chromatic aberration L* value on the fruit surface is synchronously collected to construct a two-dimensional judgment space; A dynamic threshold band is set in the judgment space, and the fruits are divided into two levels: semi-ripe fruits and fully-ripe fruits, and an overlapping buffer band is reserved between the two levels; After grading, the system automatically assigns a maturity identity code to each fruit and triggers the subsequent targeted pretreatment path accordingly; S112. Targeted pretreatment: Semi-ripe fruit path: The semi-ripe fruits are placed in a vacuum-atmospheric pressure cyclic impregnation device, and are subjected to negative pressure penetration and atmospheric pressure uniform coating with a low-concentration chitosan functional solution to form an edible antibacterial film on the fruit surface; Fully-ripe fruit path: A micron-level atomization device is used to evenly spray a vitamin C functional solution on the fruit surface.

3. The method for low-temperature post-ripening of crabapple seeds in a sand-free cold storage according to claim 1, characterized in that, The detection method for the micro-damage grading described in step S1 is as follows: S121. High-resolution backlight imaging acquisition: An industrial camera is used in combination with an adjustable LED backlight board to perform 360° rolling shooting on a single fruit to obtain a shadowless and high-contrast original image; S122. Micro-damage feature extraction and quantification: The original image is converted into a grayscale image, and a full-fruit grayscale histogram is established; Based on the average grayscale value G0 of the normal fruit skin, dark areas with a grayscale value ≤ (G0 - 15%) and an area ≥ 0.1 mm² are automatically marked as suspected damages; The proportion of the suspected damage area and the maximum Feret diameter are calculated synchronously to generate a damage index DI; S123. Three-level grading criteria: Non-damaged fruits: DI = 0, the fruit surface grayscale is uniform, without scratches or depressions; Mildly damaged fruits: 0 < DI < 5%, and the maximum scratch width ≤ 0.5 mm or the depression area < 1 cm²; Severely damaged fruits: 5% ≤ DI ≤ 10%, and the scratch width > 0.5 mm but ≤ 2 mm or the depression area is 1 cm² - 3 cm²; S124. Automatic shunting and marking: Every time the vision system detects a mildly or severely damaged fruit, it triggers a high-speed air jet sorting mechanism to shunt the fruit to the corresponding processing channel and assign a damage level identity code.

4. The method for low-temperature post-ripening of crabapple seeds in a sand-free cold storage according to claim 3, characterized in that, The targeted repair method for the micro-damage described in step S1 is as follows: For slightly damaged fruit: Spray the damaged area with a 0.03% chitosan-nano silver composite solution at a rate of 0.5-1 mL / cm² of the damaged area, and let it stand for 5 minutes to form a transparent protective film. Severely damaged fruit: The damaged area is treated with low-temperature plasma, and the residual material on the damaged surface is wiped off with a sterile dry cloth after treatment.

5. The method for low-temperature post-ripening of crabapple seeds in a sand-free cold storage according to claim 1, characterized in that, The adaptive precooling based on maturity and damage level described in step S2 includes the following steps: S21. Within the same precooling chamber, based on the interactive grading results of fruit maturity and surface damage, differentiated precooling temperature ranges, durations, and cooling wind speeds are matched in real time, with the core temperature ≤2℃ as the unified endpoint judgment index. S22. If a single precooling fails to reach the endpoint, the system will automatically extend the precooling time and retest until the core temperature meets the requirement of ≤2℃.

6. The method for low-temperature post-ripening of crabapple seeds in a sand-free cold storage according to claim 1, characterized in that, The cold storage zoning and local temperature and humidity compensation method described in step S3 is as follows: S311 Cold storage zoning: The post-curing cold storage is divided into 3 functional zones: evaporator zone, central zone, and corner zone. 3 temperature and humidity monitoring points are evenly set up in each zone. S312, Local Compensation Control: When the temperature in the evaporator zone is ≤-0.5℃, activate the built-in 500W electric heating wire in that zone to restore the temperature to 0~0.5℃; when the humidity in the corner zone is ≤62%, turn on the built-in ultrasonic humidifier in that zone to increase the humidity to 68-70%; after compensation control, ensure that the temperature deviation of the three functional zones is ≤±0.3℃ and the humidity deviation is ≤±2%.

7. The method for low-temperature post-ripening of crabapple seeds in a sand-free cold storage according to claim 1, characterized in that, The dynamic parameter adjustment logic based on real-time monitoring of embryo moisture in step S3 is as follows: S321. Seed embryo moisture monitoring: Random samples were taken every 12 hours during the after-ripening period, and the seed embryo moisture was measured by low-temperature freeze-drying method. S322. Phased parameter adjustment: Moisture reduction phase: Maintain the storage temperature at 0℃–1℃, while increasing O2 and decreasing CO2 to accelerate moisture outflow; Moisture transition phase: Lower the storage temperature to -0.5℃–0.5℃, while decreasing O2 and increasing CO2 to slow down the rate of water loss; Moisture target achievement phase: Adjust the storage temperature back to 0℃–1℃, while increasing O2 and decreasing CO2 to stabilize the moisture content of the seed embryo within the target range. S323. Dormancy release verification: After the seed embryo moisture reaches the target range, the endogenous gibberellin and abscisic acid content are measured. Low-temperature ripening is stopped only when gibberellin is ≥ 1.8 times the initial value and abscisic acid is ≤ 58% of the initial value.

8. The method for low-temperature post-ripening of crabapple seeds in a sand-free cold storage according to claim 7, characterized in that, The phased parameter adjustment process also includes a predictive feedback method based on the rate of change of embryo moisture, comprising the following steps: S331. Real-time rate calculation: Based on the post-ripening starting point, samples are taken at fixed time intervals to establish the seed embryo moisture decay curve and calculate the average moisture change rate V in the current period. S332. Dual-limit judgment of rate and threshold: The system has a built-in variable threshold group {Vmin, Vmax} that matches the stage, which is used to identify after-ripening lag and dehydration stress, respectively. S333, Predictive fine-tuning of gas parameters: When V > Vmax, dehydration is deemed excessive, and the O2 volume fraction is immediately reduced, the CO2 volume fraction is increased, and the after-ripening temperature is appropriately lowered to suppress respiration intensity; when V < Vmin and continues to exceed the set duration, hysteresis risk is deemed, and the O2 volume fraction is immediately increased, the CO2 volume fraction is reduced, and the after-ripening temperature is appropriately increased to accelerate metabolism. S334, Dynamic target threshold drift: During the moisture transition phase, if V is consistently lower than Vmin, the system will automatically raise the starting moisture threshold for subsequent moisture attainment phases. S335. Closed-loop verification: After each gas fine-tuning, continue to monitor the V value in the subsequent period. If V still exceeds the threshold zone, repeat the fine-tuning until V returns to the safe range to ensure that the moisture of the seed embryo decreases steadily along the set trajectory. When the two indicators of endogenous hormones meet the standards, end the low-temperature ripening.

9. The method for low-temperature post-ripening of crabapple seeds in a sand-free cold storage according to claim 1, characterized in that, In step S3, the standardized stacking is a V-shaped structure with a bottom width of 1.2m, a top width of 0.6m, a stack height of 0.8m, an interlayer gap of 3cm, and an adjacent stack spacing of 0.5m.

10. The method for low-temperature post-ripening of crabapple seeds in a sand-free cold storage according to claim 1, characterized in that, In step S3, the gas is directed to flow along the V-shaped stacking slope by setting side air outlets on both sides of the cold storage and return air valves on the top; and CO2 sensors are set at different depths in the stack. When the CO2 concentration is detected to be ≥2%, the side air velocity and air exchange frequency in the corresponding area are automatically increased.

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