How to preserve fresh spades

The nutritional value of walnuts is very high. Because the kernel inside the walnut is very similar to the human brain, everyone believes that eating some walnuts has the effect of nourishing the brain. This statement is very correct. Walnuts taste very fragrant and contain a lot of oil. Most people eat walnuts, and the storage time of walnuts is very long. Otherwise, how should fresh walnuts be preserved?

1. Storage characteristics of walnuts

Walnut is a dried fruit with high nutritional value and is relatively durable in storage. The walnut fruit has a bract outside, and the kernel is covered with a hard seed shell (walnut shell) inside the bract. The maturity period of walnut bract and kernel is inconsistent, and the kernel often matures first and the bract matures later. Walnuts must reach full maturity before they can be harvested. The characteristics of a fully mature walnut are that the exocarp turns from green to yellow, cracks appear on the top, and the involucre splits naturally and is easy to peel off. The walnut shell is hard and yellowish-white or brown. The optimum harvesting period is when 80% of the walnuts on the tree are ripe. After harvesting, walnuts for storage must be removed from the involucre, rinsed, dried, insect-proofed and sterilized before they can be stored. Walnuts often become moldy, infested by insects and deteriorate during storage, so better management is required. The storage place must be cool, dry, ventilated and away from light. Walnuts are best refrigerated at a low temperature of around 5 degrees and a relative humidity of 50%-60%.

2. Storage of walnuts at room temperature

Walnuts can be stored at room temperature in two ways: dry storage and wet storage.

(1) Dry storage: Place the walnuts with the green skin removed in a dry and ventilated place to dry. When the walnut membrane breaks easily when bent, the seed coat and kernel are difficult to separate, and the kernel color is consistent inside and outside, it can be stored. Put the dried walnuts in a sack and place it in a ventilated, cool room that is not directly exposed to high-pressure light. During storage, prevent rodent damage, mildew, and fever.

(2) Wet storage: dig a ditch 1 meter deep, 1-1.5 meters wide and with a length that depends on the storage capacity in a high and dry area with good drainage and sheltered from the wind. First, spread a layer of clean wet sand about 10 cm thick on the bottom of the ditch. The humidity of the sand should be such that it can be kneaded into a harmonious state but without releasing water. Then, layer upon layer of walnuts and sand are laid, and the space between the ditch walls and the walnuts is filled with wet sand, leaving no gaps. When it is about 20 cm away from the ditch mouth, cover it with wet sand to the same level as the ground, and pile up soil on the sand to form a ridge shape, with a span greater than the width of the ditch. Drainage ditches are dug around the ditch to prevent too much rainwater from seeping in and causing excessive humidity, which can easily cause the walnuts to become moldy and rot. When the length of the ditch exceeds 2 meters, a handful of tightly tied straw should be erected every 2 meters as a ventilation hole when storing walnuts. The height of the straw should be such that the "roof ridge" is exposed. The thickness of the soil on the "roof ridge" varies with the weather, and it needs to be thicker in cold areas in winter.

3. Store walnuts in plastic film tents or bags

The walnuts that have been harvested and processed in time are bagged and piled into stacks, stored in a low-temperature place and covered with a large plastic film tent. Carbon dioxide gas is filled into the tent (nitrogen can also be filled) to reduce the oxygen concentration. The carbon dioxide content can be quite high at the beginning of storage, reaching 50%, and then maintained at around 20%. The oxygen content is around 2%, which can prevent the kernel fat and oxidation deterioration, avoid the flavor spoilage and quality decline, and prevent the fruit from mold and insects. Sealed storage using plastic tents should be carried out in low temperature and dry seasons to maintain low humidity in the tent.

In the south, the temperature is still high and the air humidity is high in late autumn and early winter. Walnuts can be harvested and stored for later use. Pay attention to adding desiccant and lowering the temperature. It is best to store in a large tent in a ventilated warehouse or cold storage.