How grain coolers work
Grain refrigerators extract from grain and its surrounding air what can be dangerous to it: heat and water. Lowering the temperature and humidity protects the harvest even without chemical treatment.
Grain protection starts even before storage. The grain store should be completely emptied and cleaned thoroughly. Corners, joints and crevices in particular create survival spaces for insects. Pests can survive under old grain and dust, and in cracks and holes. Such potential refuges should therefore be cleaned or eliminated.
The conveying equipment should also be cleaned and function properly so as not to damage the conveyed bulk. For grain beetles and other species that cannot feed on intact grain, broken grains are an easy meal. The cleaning of the warehouse with pesticides must be carried out in accordance with regulations and must be strictly documented. Constructional measures such as securing exhaust air holes with meshes or grilles help keep birds and rodents away from the grain. Bought-in grain should be checked carefully before transfer to stores.
Field fungi (primary fungi) are introduced to the store with the harvest and it is from the primary fungi that the storage fungi (secondary fungi) develop. Under favourable conditions, these moulds produce highly toxic mycotoxins that endanger human and animal health. In pigs, for example, they cause reduced appetite, reduced growth and fertility problems. Highly contaminated feed can kill farm animals. The EU therefore prescribes strict limit values for mycotoxins.
Heat and moisture stimulate the metabolism of moulds and promote the formation of mycotoxins. If the crop remains uncooled, the fungi find ideal growing conditions.
Growth of various organisms dependent on moisture and temperature
Insect infestation can significantly damage stored grain. Eating, excrement and the rapid reproduction of many pests lead to loss of substance and deterioration in quality.
Insects often spread inconspicuously in the loose grain. In many cases, an infestation with grain beetles, for example, only becomes apparent when there is a mass hatching of new beetles. Since the grain beetle has a generation cycle of only 25 days under optimal conditions, by the time it is notice it may already be too late. Grain beetles lay an egg every day, so they can be present in the affected cereals at any stage of development. Pesticide control only kills developed beetles. Eggs, larvae and pupae lodge in sealed grains where they are protected.
Depending on the climate zone, the grain is exposed to different types of pests. Insects are sensitive to temperature, their activity fluctuates depending on the ambient temperature. If the temperatures are too low, they become dormant: their metabolism and reproductive capacity are reduced.
Both insects and mould can only survive in the grain if they find suitable environmental conditions. This is where grain cooling comes in: By regulating humidity and temperature, it combats both threats at the same time. The grain moisture is usually set to 14.5%, the optimal protection temperature differs depending on the crop. Rapeseed, for example, has a relatively high specific heat development and must therefore be cooled. Below 15 °C, even cold-resistant pests start to fall into the dormancy (see figure).
A grain temperature of at most 15 °C therefore provides effective protection against insect damage: it paralyses the development and multiplication and thus prevents damage to the grain by eating and excrement.
The extraction of heat and moisture also prevents the spread of mould and the associated contamination with mycotoxins. In addition to protection against spoilage, insect damage and the spread of fungi, the cooling of the grain maintains important properties of the grain. In this way, the germ quality of grain, rice, corn, seeds and malting barley is maintained over a long period of time.
As the global average temperature rises, so does the risk of insect crop loss. Warm temperatures favour the high metabolisms and higher growth rates of the pest populations. Researchers therefore predict additional crop losses of 10 - 25% per 1 °C global warming.
If the average temperature rises by 2 °C, 213 million tons of maize, wheat and rice alone will be destroyed by insect pests. Especially in temperate growing areas such as Europe, North America or China, the effects of insect damage will increase dramatically with climate change. Harvesting methods such as grain cooling help to at least partially contain these losses.
FrigorTec offers the right grain cooling device for the preservation of grain in every climate zone. Please select the climate zone in which your plant will operate:
The GRANIFRIGOR™ Europe range of grain cooling units are performance- and energy consumption-optimised for the temperature and humidity of European temperate conditions.
The GRANIFRIGOR™ Subtropic grain cooling units are performance- and energy consumption-optimised for the temperature and humidity of the subtropical climate with tropical summers and non-tropical winters.
The GRANIFRIGOR™ Tropic grain cooling units are performance- and energy consumption- optimised for the temperature and humidity of the tropical climate.
The special grain cooling units for hot dry countries of the GRANIFRIGOR™ Desert series are performance- and energy consumption-optimised for hot desert climates.
The ventilation dryers of the GRANIVENT™ series are the ideal supplement to GRANIFRIGOR™ grain dryers. They are used to aerate the grain immediately after harvesting.
Our experts will be happy to advise you on the planning and implementation of your projects. Together we will find the tailor-made solution for your grain cooling requirements.