Principle and technology of low temperature storage

Low-temperature grain storage is a technology that uses natural low-temperature conditions or mechanical refrigeration equipment to reduce the temperature of stored grain in the silo, and insulates the stored grain to ensure that its average temperature during storage is maintained at a low temperature (15 ℃) or the standard low temperature (20 ℃).

1. Principle of low temperature storage

Low temperature can inhibit the growth and reproduction of molds: the activities of food microorganisms are mainly affected by temperature and moisture inside a silo. Molds will grow in a warm grain pile that has a moisture of 13.5% to 15.0% as long as it has enough time. Low temperature may inhibit the activity of molds: generally, microorganisms cannot develop below 0℃. The inhibitory effect of low temperature on microorganisms is also affected by moisture. The temperature would be lower if grain has more moisture content, and the temperature would be higher if grain has less moisture content. Therefore, it is better to control the moisture content of grain when we use low temperature to inhibit the growth of molds. Also, a low temperature can prevent some bacteria strain producing toxic substance and ensure the safety of grain .

Low temperature is conducive to maintaining the quality of food: for grains with normal moisture content, as long as the grain temperature is controlled below 15°C, the grain quality loss caused by the respiration and other decomposition of the grains can be reduced, and the grain will enter into a dormant state which helps to maintain the freshness and germination power of grain. For areas without drying equipment, low temperature storage system is a better way to store high-moisture grains.

2. Low temperature storage technology:

Natural low temperature grain storage: a technology that uses natural cold sources to reduce and maintain grain temperature, making full use of favorable natural conditions and conforming to the concept of energy saving and environmental protection. But it is greatly restricted by geographical location, climatic conditions and seasons.

Under normal circumstances, in order to alleviate the external heat from entering grain pile, we need use thermal-insulating material to cover grain surface to reduce heat transfer. Moreover, the silo roof is improved to reduce silo temperature and silo wall is added thermal-insulating material or coated with thermal-insulating paint.  

Mechanical aeration for low temperature grain storage: grain temperature is lowered and maintained at a low temperature through mechanical aeration system which can cool grain pile by using natural cold air.

3. Mechanical refrigeration for low temperature grain storage

A grain storage technology that uses the cold source generated by mechanical refrigeration equipment (including grain coolers, air conditioners, etc.) to reduce the temperature of grain stored in silo and realize low temperature grain storage. 

As the safest, reliable, reasonable and most environmentally friendly technology in the world, low temperature storage will gradually show its economic and social benefits in the long run.