Winter Storage Methods and Fresh-Keeping Techniques for Napa Cabbage
Winter Storage Techniques for Napa Cabbage
There are many methods for storing napa cabbage, mainly cellar storage, ventilated storage, and pit storage, as well as mechanically assisted ventilation or mechanical refrigeration storage in large warehouses.
1. Pit storage Suitable for winter napa cabbage storage in southern Northeast China, southern North China, and the provinces of Shandong and Henan. Dig a shallow trench with a depth roughly equal to the height of the cabbage and a width of about 1 m; the length is unlimited. The dug trench should be left to dry for 2-3 days to reduce humidity.
Place the napa cabbage in the trench with the roots pointing downward and the tops level, so that the soil cover will be of uniform thickness. Pit storage should be carried out on an overcast day or in cooler weather whenever possible, so that a lower temperature is maintained in the trench. After the cabbage is arranged, decide whether to cover it and how thick the cover should be according to the weather conditions at the time. Generally, in the early storage period, when the temperature is relatively high, no cover may be applied, or a little covering material may be used for shade. As the weather gradually turns colder, dry soil can be used for covering; try not to use damp clods of soil. The soil cover should be applied in stages, with the thickness generally governed by the principle that the napa cabbage is not damaged by heat and the soil cover is not frozen through.
In areas with a relatively thin frozen soil layer, an inverted method of storage can also be used. Stand the selected napa cabbage upright in the prepared trench with the roots pointing upward and cover with soil (so that the roots are just buried), then pour a small amount of water on the soil surface so that the cabbage maintains weak growth during storage. This inverted pit storage method is suitable for storing napa cabbage that is about 70% headed. Cabbage stored by the inverted method is not easily damaged by freezing and can increase in weight; however, note that the trench should not be dug too deep or too wide, and the soil cover should not be too thick.
Using the pit storage method to store napa cabbage is simple and easy to carry out, with little water loss and small weight loss; however, it does not allow ventilation, makes it difficult to regulate temperature and humidity, and the storage period is relatively short.
2. Cellar storage Cellar storage of cabbage is relatively common, but the methods differ from region to region. The south is relatively warm, so aboveground cellars are mostly used; the cold northern regions mostly use underground cellars; and the Central Plains region mostly uses semi-underground cellars.
After pretreatment, the napa cabbage is put into the cellar and stacked. Generally, along the length of the cellar, stacks are built one cabbage wide and about 2 m high, and several stacks can be built in one cellar. To prevent the stacks from collapsing, wooden poles or simple wooden frames can be used for support, and a certain distance should be kept between stacks to allow ventilation and management. The stacking methods vary from place to place, but all should follow the principles of facilitating ventilation without heat damage, facilitating insulation without freezing, facilitating stacking without collapse, facilitating management without wasting labor, requiring fewer turnings of the cabbage, and keeping various losses low.
For stacked cabbage, the temperature difference between the top and bottom is generally relatively large. At regular intervals, the stack should be turned once, moving the upper cabbage to the lower part to balance temperature and humidity, and at the same time removing cabbage unsuitable for continued storage from the cellar.
Management during the storage period is roughly divided into three stages: the early storage period (from being put into the cellar to "Major Snow"), when the cellar temperature is relatively high and the cabbage releases more heat through respiration, so the vents should be opened every day when the outside temperature is lower than the cellar temperature, in order to lower the cellar temperature and remove harmful gases. At this time, the cabbage should be turned frequently, and the interval between turnings should gradually be extended. The middle storage period ("Major Snow" to "Start of Spring") coincides with the cold season, when both the cellar temperature and the cabbage temperature have already dropped and the respiration heat of the cabbage has decreased, so the main task is to prevent freezing; close the vents, and if necessary, carry out short periods of ventilation around noon when the temperature is relatively high. During this period, reduce the number of turnings and extend the interval between turnings, and during turning try to protect the outer leaves so as to protect the inner leaves. In the late storage period (after "Start of Spring"), the temperature gradually rises, and the cellar temperature rises accordingly, so ventilation at night should be the main method to lower the cellar temperature. During this period, the cabbage should be turned frequently.
1. Pit storage Suitable for winter napa cabbage storage in southern Northeast China, southern North China, and the provinces of Shandong and Henan. Dig a shallow trench with a depth roughly equal to the height of the cabbage and a width of about 1 m; the length is unlimited. The dug trench should be left to dry for 2-3 days to reduce humidity.
Place the napa cabbage in the trench with the roots pointing downward and the tops level, so that the soil cover will be of uniform thickness. Pit storage should be carried out on an overcast day or in cooler weather whenever possible, so that a lower temperature is maintained in the trench. After the cabbage is arranged, decide whether to cover it and how thick the cover should be according to the weather conditions at the time. Generally, in the early storage period, when the temperature is relatively high, no cover may be applied, or a little covering material may be used for shade. As the weather gradually turns colder, dry soil can be used for covering; try not to use damp clods of soil. The soil cover should be applied in stages, with the thickness generally governed by the principle that the napa cabbage is not damaged by heat and the soil cover is not frozen through.
In areas with a relatively thin frozen soil layer, an inverted method of storage can also be used. Stand the selected napa cabbage upright in the prepared trench with the roots pointing upward and cover with soil (so that the roots are just buried), then pour a small amount of water on the soil surface so that the cabbage maintains weak growth during storage. This inverted pit storage method is suitable for storing napa cabbage that is about 70% headed. Cabbage stored by the inverted method is not easily damaged by freezing and can increase in weight; however, note that the trench should not be dug too deep or too wide, and the soil cover should not be too thick.
Using the pit storage method to store napa cabbage is simple and easy to carry out, with little water loss and small weight loss; however, it does not allow ventilation, makes it difficult to regulate temperature and humidity, and the storage period is relatively short.
2. Cellar storage Cellar storage of cabbage is relatively common, but the methods differ from region to region. The south is relatively warm, so aboveground cellars are mostly used; the cold northern regions mostly use underground cellars; and the Central Plains region mostly uses semi-underground cellars.
After pretreatment, the napa cabbage is put into the cellar and stacked. Generally, along the length of the cellar, stacks are built one cabbage wide and about 2 m high, and several stacks can be built in one cellar. To prevent the stacks from collapsing, wooden poles or simple wooden frames can be used for support, and a certain distance should be kept between stacks to allow ventilation and management. The stacking methods vary from place to place, but all should follow the principles of facilitating ventilation without heat damage, facilitating insulation without freezing, facilitating stacking without collapse, facilitating management without wasting labor, requiring fewer turnings of the cabbage, and keeping various losses low.
For stacked cabbage, the temperature difference between the top and bottom is generally relatively large. At regular intervals, the stack should be turned once, moving the upper cabbage to the lower part to balance temperature and humidity, and at the same time removing cabbage unsuitable for continued storage from the cellar.
Management during the storage period is roughly divided into three stages: the early storage period (from being put into the cellar to "Major Snow"), when the cellar temperature is relatively high and the cabbage releases more heat through respiration, so the vents should be opened every day when the outside temperature is lower than the cellar temperature, in order to lower the cellar temperature and remove harmful gases. At this time, the cabbage should be turned frequently, and the interval between turnings should gradually be extended. The middle storage period ("Major Snow" to "Start of Spring") coincides with the cold season, when both the cellar temperature and the cabbage temperature have already dropped and the respiration heat of the cabbage has decreased, so the main task is to prevent freezing; close the vents, and if necessary, carry out short periods of ventilation around noon when the temperature is relatively high. During this period, reduce the number of turnings and extend the interval between turnings, and during turning try to protect the outer leaves so as to protect the inner leaves. In the late storage period (after "Start of Spring"), the temperature gradually rises, and the cellar temperature rises accordingly, so ventilation at night should be the main method to lower the cellar temperature. During this period, the cabbage should be turned frequently.