Why does the quality of soybeans deteriorate during storage?

In the first stage, the storage period is less than 2 years, and the soybean quality has no obvious deterioration, and the soybean is in a normal state;

In the second stage, after 2 to 3 years of storage, the quality begins to deteriorate, and it is no longer suitable for seeds. The fatty acid value changes, and other quality indicators have also changed greatly, which is used for processing non-staple foods or oil extraction, the yield is reduced, the quality is deteriorated, and the soybean should not be stored continuously;

In the third stage, the soybean quality deteriorated significantly after 3 to 4 years of storage. The fatty acid content is high, and the oil yield is low when oil is extracted from this soybean. This is because the higher the fatty acid value, the more serious the oxidation of the oil, a large number of oxidation products need to be removed in the process of oil extraction, affecting the oil yield, which not only increases the production cost, but also some of the oxidation products that have not been removed will change the color of the oil and produce peculiar smell, thus affecting the edible value of the oil.

The quality deterioration of soybean in the storage process can be roughly divided into three stages: the first stage, the storage period is less than 2 years, the quality of soybean has no obvious deterioration, and the soybean is in a normal state; In the second stage, after 2 to 3 years of storage, the quality begins to deteriorate, and it is no longer suitable for seeds. The fatty acid value changes, and other quality indicators have also changed greatly, which is used for processing non-staple foods or oil extraction, the yield is reduced, the quality is deteriorated, and the soybean should not be stored continuously; In the third stage, the soybean quality deteriorated significantly after 3 to 4 years of storage.

The fatty acid content is high, and the oil yield is low when oil is extracted from this soybean. This is because the higher the fatty acid value, the more serious the oxidation of the oil, a large number of oxidation products need to be removed in the process of oil extraction, affecting the oil yield, which not only increases the production cost, but also some of the oxidation products that have not been removed will change the color of the oil and produce peculiar smell, thus affecting the edible value of the oil.

Any food will spoil after being left at room temperature for a while.

There are 3 main causes of food spoilage:

1. Microorganisms play a role. Microorganisms are everywhere in the environment, and food is easily contaminated by microorganisms during production, processing, transportation, storage, and marketing. As long as the temperature is right, microorganisms will grow and multiply and break down nutrients in food to meet their own needs.

At this time, the protein in the food is destroyed, and the food will emit a foul and sour taste, lose its original toughness and elasticity, and the color will also change.

2. The role of enzymes. There are many enzymes in animal food, and under the action of enzymes, the nutrients of the food are broken down into a variety of lower products. The rice and fruit rot that we usually see are because the carbohydrates are broken down by enzymes and fermented.

3. Chemical reactions of food. Fats are easily oxidized, resulting in a series of chemical reactions, and the oxidized fats have a strange smell, such as fat meat will turn from white to yellow.

Spoiled food not only changes its appearance, loses its original color, aroma and taste quality, but also reduces its nutritional value, and also contains corresponding toxins that endanger human health.

Soybean has strong hygroscopicity, easy to mold, soybean seed coat is thin, germination hole is large, and the moisture absorption capacity is stronger than that of wheat and corn. After the soybean absorbs moisture and returns to moisture, the volume expands and is very easy to mold. At first, the bean grains were soft, the seed coat was gray and white, and there was a slight peculiar smell, and then the bean grains were swollen and deformed, the umbilicus was red, the broken grains appeared colonies, and the quality of the beans deteriorated sharply.

Soybean is easy to go oil, red change, after high temperature season storage of soybeans, often appear two ** leaves by the umbilicus color red, after the cotyledons red deepened and expanded, serious oil immersion, at the same time high temperature and high humidity also make soybean germination ability reduced. After the soybean oil is red, the oil yield decreases, the color of soybean oil deepens, the tofu has a rancid taste, and the color of soybean milk is red. Strictly control the storage moisture, and the long-term storage moisture of soybeans should not exceed 12%.

After the soybeans are harvested, they are thoroughly dried on the pods before threshing. Soybeans with high moisture content after storage can be treated by sun exposure, but they can only be put into the warehouse after being cooled.

Timely ventilation, heat dissipation and humidity The moisture between the soybean grains in the newcomer library is uneven, coupled with the ripening effect of soybeans, the damp heat in the pile is easy to accumulate, causing heat and mildew, so it is necessary to ventilate in a timely manner, dissipate heat and dissipate humidity.

Low-temperature closed storage After entering the winter, ventilation and cooling should be strengthened, and the gland or plastic film should be used for closed storage before the spring is warm, so that it can generally be safely spent in summer.

The soybean harvest should be carried out between the yellow and full maturity periods. Harvesting too early or too late will reduce the yield and quality of soybeans. Moreover, the timely harvest should be flexibly mastered according to the climatic conditions, if the soybean maturity period encounters drought climate, it can be harvested early, and it can be harvested in the yellow maturity period; If the soybean maturity period encounters a lot of rain and high air humidity in the year, it should be harvested late.

Manual harvesting should be carried out when 10% of the leaves of soybean plants have not fallen off, and should be harvested in the morning on a sunny day; Mechanical harvesting should be carried out when all the leaves of the plant have fallen and the beans have returned to the round.

According to the storage characteristics of soybean seeds, the following technical points need to be mastered:

1) Expose the pods to the sun and dry them thoroughly. Soybean seeds should be dried with pods before threshing. Soybean seeds have large grains, thin skin, poor heat resistance, and the threshing seeds should avoid exposure to the scorching sun, and the temperature and drying speed should be strictly controlled when the fire is drying, so as to avoid cracking and peeling due to uneven drying.

The moisture content of soybeans should be less than 12% for safe storage, and there is a risk of mildew if the moisture exceeds 13%. Soybean seeds have strong water absorption, so they should be strictly protected from moisture and kept dry after storage in the warehouse.

2) Reasonable stacking and correct management. The stacking and storage management of soybean seeds depends on the moisture content of the seeds. Low-moisture seeds can be stacked up to meters tall and managed in closed storage.

If the moisture content is more than 12%, especially the newly harvested seeds, the stacking height should be appropriately reduced according to the different moisture levels, and ventilation storage should be adopted. Generally, the moisture is 12% to 14%, and the pile height should be less than 1 meter; The moisture content is more than 14%, and the pile height should be less than meters.

3) Low temperature sealing. Due to the high fat content of soybean and the small thermal conductivity of fat, soybean has poor heat conductivity, which is not easy to cool down under high temperature conditions, and is easy to cause red transformation, so low temperature and closed storage methods should be adopted. Generally, soybeans can be transferred or frozen out of the warehouse in the cold winter season, so that the seed temperature can be fully reduced and then sealed at low temperature.

In the planting and storage of soybeans, we should pay attention to insect pests.

There's no harm in drying it.

Soybean storage characteristics: soybean protein and fat content is high, and the grain structure is relatively special, which has the storage characteristics of high water content, strong water absorption, high temperature and easy deterioration, long maturity period and easy precipitation of oil.

Soybean storage requirements: The quality of soybeans should meet the quality standards of at least grade III in GB 1532-2009.