A method for improving the quality of ginger during post-harvest storage

Abstract

The present invention belongs to the technical field of fruit and vegetable preservation, and specifically discloses a method for improving the quality of ginger during storage after harvest. The method of the present invention comprises the following steps: placing ginger in a constant temperature environment of 15±2°C, adjusting the storage environment to an anaerobic environment, the humidity to 85~95%, the volume ratio of C4F8 at 25°C standard atmospheric pressure to 1~5%, and applying a low-voltage electrostatic field treatment at the same time. The storage method of the present invention is simple, the storage cost is low, no antibacterial agent and other storage auxiliary reagents are added, and a negative ion, anaerobic, and high-humidity storage environment is formed during the storage process. The antibacterial effect is good, and the corruption and deterioration of ginger during storage can be effectively inhibited. At the same time, the germination and respiration of ginger itself are also inhibited, and the quality of ginger is kept good. The method is green, environmentally friendly, efficient and safe, and has good market prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of fruit and vegetable preservation, and particularly relates to a method for improving the quality of post-harvest ginger during storage. Background Art

[0002] Ginger (Zingiber officinale Roscoe) is a perennial herbaceous plant rhizome of the Zingiberaceae family. It has a unique spicy taste and is a traditional economic crop for both medicinal and edible purposes. With the expansion of ginger planting area in my country, ginger is put on the market in large quantities and concentrated in time. Therefore, the use of appropriate storage and preservation technology is an important means to ensure the year-round supply of ginger and regulate the surplus and shortage of the market. Therefore, post-harvest storage of ginger is one of the key technologies for the development of the ginger industry. Traditional ginger storage methods such as sand storage, cellar storage, and cave storage have high labor costs, and ginger is prone to mold, rot, and sprout during storage, which seriously affects the shelf life and commodity value of fresh ginger. At present, the research on ginger storage technology at home and abroad mainly uses preservative treatment, irradiation treatment, and gas conditioning treatment to preserve ginger after harvest, but it has not completely solved the problems of ginger being prone to water loss, sprouting, and being infected by microorganisms and rotting during storage. There is an urgent need to find some methods that can safely and efficiently inhibit the germination of ginger during storage. Therefore, how to improve the quality of ginger during storage is one of the urgent problems to be solved in the ginger industry.

[0003] At present, ginger is put on the market in large areas in my country from October to November, and the price of ginger fluctuates greatly. In order to achieve continuous supply and price stability in the ginger market, the storage of fresh ginger has become a necessity. At present, there are mainly the following methods for storing ginger: 1. Closed storage Strictly select ginger, leave the better quality ones scattered in the warehouse, cover them with straw bags and straw curtains for storage. Then build a brick wall in the south direction of the warehouse to separate a small warehouse, and apply mud on the brick wall to block the brick seams to prevent cold wind from blowing in. Pile ginger inside the brick wall. The ginger pile is about 2 meters high. Several ventilators made of reeds are evenly placed in the pile to the top for ventilation. When stacking, leave no gaps in the corners, and the middle can be slightly loose. Immediately after stacking, close the top with mud or straw bags. The storage warehouse should not be too large. Generally, it is appropriate to stack about 5,000 kilograms per warehouse. The warehouse temperature is generally controlled at 18-20℃. When the temperature drops, the covering can be increased to keep warm; if the temperature is too high, the covering can be reduced to dissipate heat and cool down. 2. Pit storage In places where the groundwater level is high, pit burial is often used to store ginger. The depth of the pit is based on the principle of not leaking water. It is generally 1 meter deep and about 2 meters in diameter. It is wide at the top and narrow at the bottom. It can be round or square. One pit can store about 2,500 kilograms. The total thickness of the covering soil is 60 cm to 65 cm. The principle is to maintain a suitable storage temperature in the pile. The top of the pit is made of straw to form a round pointed top to prevent rain. Drainage ditches are set up around it. Wind barriers are set up on the north side to prevent cold. 3. Sediment burial The burial pit is made of bricks and stones in a warehouse or basement. The height is about 0.8 meters, the width is about 1 meter, and the length is unlimited. When storing, a layer of sediment about 5 cm thick and with a water content of about 10% is first spread on the bottom of the pit, and finally covered with sediment to prevent the ginger from being exposed to the air. 4. The air raid shelter stores one layer of sand and one or two layers of ginger, which are stacked into rectangular piles 1 meter high and 1 meter wide. Each pile weighs 1,250-2,500 kilograms. In the middle of the pile, a ventilation bundle with a diameter of about 10 cm made of thin bamboo poles is placed, and a thermometer is placed in the well to measure the temperature of the pile. The pile is sealed with wet sand on all sides. After the pile is sealed, the cave door is covered and air holes are left on the hole to prevent cold wind from blowing in. The above traditional storage methods of ginger have a short storage time. After storage, the surface of the ginger is dry, and the ginger inside also loses water to varying degrees, which seriously affects the quality of ginger. Summary of the invention

[0004] In order to prolong the shelf life of fresh ginger and reduce the dehydration, germination, decay and other phenomena of fresh ginger during storage, the present invention provides a method for improving the quality of ginger during storage after harvest, which specifically comprises the following steps: After harvesting ginger, select ginger pieces that are free of pests and diseases, frost damage, neat, strong and without mechanical damage, and precool them in an environment of 15±2℃. Precooling ends when the center temperature of the sample drops to 15℃.

[0005] The pre-cooled ginger was placed in a constant temperature environment of 15±2°C, the storage environment was adjusted to an anaerobic environment, the humidity was 85-95%, the volume ratio of C4F8 at 25°C standard atmospheric pressure was 1-5%, and a low-voltage electrostatic field treatment was applied at the same time.

[0006] Among them, the output voltage of the low-voltage electrostatic field generating device is 2500 V and the current is 0.2 mA. Its discharge plate is arranged in the storage environment to generate a low-voltage electrostatic field and form a negative ion environment.

[0007] Wherein, the anaerobic environment is composed of nitrogen and carbon dioxide.

[0008] Wherein, in the anaerobic environment, the volume ratio of CO2 at 25°C and standard atmospheric pressure is 20-30%, and the volume ratio of N2 at 25°C and standard atmospheric pressure is 65-79%.

[0009] Wherein, the electrostatic field generating device of the low-voltage electrostatic field is AC220V, 50 / 60Hz.

[0010] Beneficial Effects The invention ensures that the fresh ginger will not lose water or weight during long-term storage by keeping the storage environment sealed and keeping the environment containing 85-95% of water during storage. That is, the freshness of the ginger is ensured during storage, and the appearance, color and composition of the ginger taken out after storage are almost the same as those of the fresh ginger. Meanwhile, the anaerobic environment also inhibits the respiration of the ginger after harvesting, and the gas conditioning + low-voltage electrostatic field treatment of octafluorocyclobutane is used for the first time, so that a small amount of hydrofluoric acid will be in the environment during storage, and the additional low-voltage electrostatic field treatment can significantly inhibit the germination rate of the ginger. It can be seen from the single factor experiment that the higher the concentration of octafluorocyclobutane, the lower the germination rate, but it also has certain damage to the ginger. The invention uses the optimal octafluorocyclobutane concentration, which not only inhibits the germination of the ginger, but also significantly reduces the weight loss rate of the ginger.

[0011] From the weight loss rate, germination rate and percentage of volatile substances in ginger, it can be seen that C4F8 gas conditioning + low-pressure electrostatic field treatment can significantly maintain the original weight of ginger, that is, the breathing self-consumption during storage is minimal, and at the same time, the growth of corrupt microorganisms is inhibited, the corruption of microorganisms is reduced, and the germination of ginger is inhibited, achieving a good storage effect. The data on the percentage of volatile substances in ginger also prove that gas conditioning + low-pressure electrostatic field can keep the volatile substances in ginger stable, that is, it does not change the original flavor of ginger, and plays a good storage role.

[0012] The present invention adopts octafluorocyclobutane and a low-voltage electrostatic field to assist in the constant temperature storage for storing ginger. By controlling the temperature and implementing a low-voltage electrostatic field in the storage space, the decay of ginger during storage can be effectively improved, while the germination rate of ginger can be reduced, thereby improving the quality of ginger during storage.

[0013] The storage method of the present invention is simple and has low storage cost. No antibacterial agent or other storage auxiliary reagent is added. During the storage process, the high humidity environment of the storage environment is maintained. At the same time, the antibacterial effect is good, and the germination and respiration of the ginger itself are also inhibited. The method is efficient and safe and has good market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The storage effect of five months of controlled atmosphere + low-pressure electrostatic field DETAILED DESCRIPTION

[0015] In all embodiments of the present invention, the analysis methods of each index are as follows: ① Germination rate: The germination standard is when the first bud of the ginger tuber is 2 mm long. Germination rate (%) = number of germinated tubers / total number of tubers × 100%.

[0016] ②Weight loss rate: The weight loss rate is determined by weighing method.

[0017] ③ Volatile component analysis: 1 g of fresh ginger was weighed and put into a 20 mL screw-cap glass headspace bottle, which was sealed with a polytetrafluoroethylene-lined silicone rubber pad. A 50 / 30 µm polydimethylsiloxane (DVB / CAR / PDMS) extraction fiber head was inserted into the screw-cap glass headspace bottle. Headspace extraction was performed at 60 °C for 30 min, and the volatile components of ginger were analyzed using an Agilent-7890B / 7000B triple level 4 pole gas spectrometer (Agilent, USA).

[0018] Gas chromatography conditions: The chromatographic column was a DB-5MS quartz capillary column (60 mx 250 µm x 0.25 µm); the temperature program was: 50°C for 1.5 min, then increased to 125°C at 8°C / min, then increased to 145°C at 3°C / min, then increased to 150°C at 0.5°C / min, maintained for 10 min, and finally increased to 260 at 15°C / min, maintained for 8 min. The carrier gas was high-purity helium with a split ratio of 1:30. The mass spectrometry conditions were: electron impact (EI) ion source, electron energy 70 eV; the transmission line temperature was 280°C, the quadrupole temperature was 150°C, and the ion source temperature was 230°C; the scanning mode was ion monitoring mode, and the scanning mass range was 35~450 amu.

[0019] Example 1 A method for improving the quality of ginger during post-harvest storage, which is as follows: (1) After harvesting ginger, select ginger pieces that are free of pests and diseases, frost damage, neat, strong and without mechanical damage, and precool them at 15±2℃ for 24 hours.

[0020] (2) A 20 kg sample of ginger was randomly divided into 10 portions, each containing 2 kg of ginger. The ginger samples were packaged in 8-filament high-pressure PE bags.

[0021] (3) The ginger samples were placed in a constant temperature box at 15±2℃ for storage test. Before storage, the air in the high-pressure PE bag was first evacuated, and then the mixed fresh-keeping gas was introduced. At the same time, the humidity of the mixed fresh-keeping gas was controlled between 85% and 95%. During the storage process, this experiment was conducted under laboratory conditions. The mixed fresh-keeping gas was replenished every 1 to 3 days depending on the amount of ginger in the high-pressure PE bag. If it was a large storage warehouse, a controlled atmosphere warehouse was used to adjust the content of various gases in the storage environment until the end of storage.

[0022] (4) The low-voltage electrostatic field device used in the test experiment consists of an electrostatic field generator (AC220V, 50 / 60Hz) and a discharge plate (430 mm×230 mm). The output voltage of the electrostatic field generator is 2500 V and the current is 0.2 mA. The discharge plate generates a low-voltage electrostatic field in the low-temperature test refrigerator to form a negative ion environment.

[0023] According to the mixed fresh-keeping gas, gas storage of different components is set, and the volume fraction of each component at 25° C. standard atmospheric pressure is as follows: Group 1: CO2 accounts for 20%, N2 accounts for 79%, and C4F8 accounts for 1%:.

[0024] Group 2: CO2 accounts for 25%, N2 accounts for 72%, and C4F8 accounts for 3%:.

[0025] Group 3: CO2 accounts for 30%, N2 accounts for 65%, and C4F8 accounts for 5%:.

[0026] Group 4: CO2 accounts for 35%, N2 accounts for 58%, and C4F8 accounts for 7%.

[0027] Group 5: CO2 accounts for 40%, N2 accounts for 51%, and C4F8 accounts for 9%:.

[0028] Table 1: Ginger germination rate stored in different atmospheres Table 2: Weight loss rate of ginger stored in different controlled atmosphere environments It can be seen from the above experimental results that the higher the content of octafluorocyclobutane, the lower the germination rate, but the higher the weight loss rate. This may be because octafluorocyclobutane produces hydrofluoric acid in a low-voltage electrostatic field environment, causing the ginger cells to be destroyed and lose water, which can cause serious weight loss in ginger. Balancing the germination rate and weight loss rate, when the octafluorocyclobutane content is between 1 and 5%, the comprehensive effect of ginger weight loss rate and germination rate is best.

[0029] Example 2 A method for improving the quality of ginger during post-harvest storage, which is as follows: Adopt fresh-keeping bag atmosphere control + low-voltage electrostatic field treatment group (5) After harvesting ginger, select ginger pieces that are free of pests and diseases, frost damage, neat, strong and without mechanical damage, and pre-cool them at 15℃ for 24 hours.

[0030] (6) Select 20 kg of ginger samples and randomly divide them into 10 portions, with 2 kg of ginger in each portion. Use 8-filament high-pressure PE bags to package the ginger samples.

[0031] (7) The ginger samples were placed in a constant temperature box at 15±2℃ for storage test. Before storage, the air in the high-pressure PE bag was first evacuated, and then a mixed fresh-keeping gas was introduced. The volume fraction of each component of the mixed fresh-keeping gas under standard atmospheric pressure conditions of 25℃ was: CO2 accounted for 25%, N2 accounted for 72%, and C4F8 accounted for 3%. At the same time, the humidity of the mixed fresh-keeping gas was controlled between 85~95%. During the storage process, this experiment was conducted under laboratory conditions, so the mixed fresh-keeping gas was replenished every 1~3 days according to the amount of ginger in the high-pressure PE bag. If it is a large storage warehouse, a controlled atmosphere warehouse was used to adjust the content of various gases in the storage environment until the end of storage.

[0032] (8) The low-voltage electrostatic field device used in the test experiment consists of an electrostatic field generator (AC220V, 50 / 60Hz) and a discharge plate (430 mm×230 mm). The output voltage of the electrostatic field generator is 2500 V and the current is 0.2 mA. The discharge plate generates a low-voltage electrostatic field in the low-temperature test refrigerator to form a negative ion environment.

[0033] Control group 1 Use fresh-keeping bag (no gas conditioning) + low-voltage electrostatic field treatment group (1) After harvesting ginger, select ginger pieces that are free of pests and diseases, frost damage, neat, strong and without mechanical damage, and precool them at 15℃ for 24 hours.

[0034] (2) A 20 kg sample of ginger was randomly divided into 10 portions, with 2 kg of ginger in each portion. The ginger samples were sealed and packaged in 8-filament high-pressure PE bags.

[0035] (3) The ginger samples were placed in a constant temperature box at 15±2℃ for storage test. The ginger stored in a low-voltage electrostatic field environment (15℃) was the low-voltage electrostatic field treatment group.

[0036] (4) The low-voltage electrostatic field device used in the test experiment consists of an electrostatic field generator (AC220V, 50 / 60Hz) and a discharge plate (430 mm×230 mm). The output voltage of the electrostatic field generator is 2500 V and the current is 0.2 mA. The discharge plate generates a low-voltage electrostatic field in the low-temperature test refrigerator to form a negative ion environment.

[0037] Control group 2 Uses controlled atmosphere treatment and no low voltage electrostatic field group (1) After harvesting ginger, select ginger pieces that are free of pests and diseases, frost damage, neat, strong and without mechanical damage, and precool them at 15℃ for 24 hours.

[0038] (2) The ginger samples were placed in a constant temperature box at 15±2℃ for storage test. Before storage, the air in the high-pressure PE bag was first evacuated, and then a mixed fresh-keeping gas was introduced. The volume fraction of each component of the mixed fresh-keeping gas at 25℃ was: CO2 accounted for 25%, N2 accounted for 72%, and C4F8 accounted for 3%. At the same time, the humidity of the mixed fresh-keeping gas was controlled between 85~95%.

[0039] (3) Place the ginger samples in a constant temperature box at 15°C for storage test.

[0040] Control group 3 Use fresh-keeping bag sealed packaging without low-voltage static field group (4) After harvesting ginger, select ginger pieces that are free of pests and diseases, frost damage, neat, strong and mechanically damaged, and pre-cool them at 15°C for 24 hours.

[0041] (5) Select 20 kg of ginger samples and randomly divide them into 10 portions, with 2 kg of ginger in each portion. Use 8-filament high-pressure PE bags to package the ginger samples.

[0042] (6) Place the ginger samples in a constant temperature box at 15±2℃ for storage test.

[0043] Control group 4 (1) After harvesting ginger, select ginger pieces that are free of pests and diseases, frost damage, neat, strong and without mechanical damage, and precool them at 15℃ for 24 hours.

[0044] (2) Select 20 kg of ginger sample and randomly divide it into 10 portions, each containing 2 kg of ginger, without packaging.

[0045] (3) Place the ginger samples in a constant temperature box at 15°C for storage test.

[0046] The above experimental groups took samples in months 0, 1, 2, 3, 4, and 5 to evaluate the quality of ginger during storage.

[0047] Storage measurement indicators are as follows: Table 3: Germination rate of Example 2 group and control group Table 4: Weight loss rate of Example 2 group and control group Table 4: Percentage of volatile substances in ginger It can be seen from the weight loss rate, germination rate and percentage of volatile substances in ginger that C4F8 gas conditioning + low-pressure electrostatic field treatment can significantly maintain the original weight of ginger, that is, the respiratory self-consumption during storage is minimal, while inhibiting the growth of corrupt microorganisms, reducing microbial corruption, and inhibiting the germination of ginger, achieving a good storage effect. The data on the percentage of volatile substances in ginger also prove that gas conditioning + low-pressure electrostatic field can promote the formation of terpene volatile substances in ginger and improve the nutritional and flavor quality of ginger during storage.

Claims

1. A method for improving the quality of ginger during storage after harvest, characterized in that: The processing method comprises the following steps: The harvested ginger is placed in a constant temperature environment of 15±2℃, the storage environment is adjusted to an anaerobic environment, the humidity is 85~95%, the volume ratio of C4F8 at 25℃ standard atmospheric pressure is 1~5%, and a low-voltage electrostatic field treatment is applied at the same time.

2. The method for improving the quality of ginger during postharvest storage according to claim 1, characterized in that: The ginger is selected from ginger pieces that are free of pests and diseases, frost damage, neat, strong and mechanically damaged, and is precooled in an environment of 15±2°C.

3. The method for improving the quality of ginger during storage after harvest according to claim 1, characterized in that: The output voltage of the low-voltage electrostatic field generating device is 2500 V and the current is 0.2 mA. The discharge plate is arranged in the storage environment to generate a low-voltage electrostatic field and form a negative ion environment.

4. The method for improving the quality of ginger during storage after harvest according to claim 1, characterized in that: The anaerobic environment consists of nitrogen and carbon dioxide.

5. The method for improving the quality of ginger during storage after harvest according to claim 4, characterized in that: In the anaerobic environment, the volume ratio of CO2 at 25°C and standard atmospheric pressure is 20-30%, and the volume ratio of N2 at 25°C and standard atmospheric pressure is 65-79%.

6. The method for improving the quality of ginger during storage after harvest according to claim 1, characterized in that: The electrostatic field generating device of the low-voltage electrostatic field is AC220V, 50 / 60Hz.

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