Grain chilling results


Milled rice / paddy cooling

Rice is a staple food for over half of the world’s population and is grown on every continent except Antarctica. It has the second largest cereal production after maize with over 782 million tons recorded in 2018 (FAOSTAT) and although the production of maize is higher, rice is the by far more important food crop as most of it goes to human consumption. It is thus no wonder that the quality of rice is of utmost importance. There are thousands of varieties of rice produced around the world which are classified into three categories: short, medium and long. All rice varieties are highly sensitive and prone to breakage, discoloration, and loss of aroma. Paddy is usually harvested at high moisture levels and hence has to be dried gently to a storable moisture content. Please refer chart 1. If a grain chiller is used it is possible to store the paddy at a slightly higher moisture content and dry it down to the desired moisture content while simultaneously cooling it. In fact this procedure not only reduces drying costs and improves the product quality due to less stresses induced during the drying process, but it also reduces the electrical power and time required to chill the product inside the silo! This effect is caused by the so called evaporative cooling. As the air induced into the silo is of slightly lower moisture content than the grain, the grain will transfer part of its moisture to the air. This evaporation of water from the product to the air requires a lot of energy, which is withdrawn from the product in form of heat and the product hence cools down. This procedure also avoids any kind of stress cracks and breakage in paddy and rice, as it is a slow and controlled process. Once the grain is cold, the grain remains cold for a long period of time, due to its characteristic of being a poor heat conductor and the fact that the grain is surrounded by a layer of air. This results in numerous advantages such as significantly reducing chances of insect infestation, preserving the aroma, avoiding grain baking inside the silo, no risk of mold development and subsequent mycotoxin contamination as well as no need to recirculate the grain.


Maize cooling

Maize has the largest cereal production in the world and is used both in food as well as animal feed applications. Unfortunately it is also the crop with the highest susceptibility with regards to mycotoxins, secondary metabolites of molds, and especially the most toxic amongst them, Aflatoxin B1. According to FAO, 25% of all crops worldwide are contaminated with mycotoxins, a major concern both for human and animal health. Around 155´000 cases of liver cancer a year are attributed to mycotoxins, they lead to stunting in children and can eradicate whole life stocks if contaminated feed is fed. While the weather as well as the field conditions influence the growth of some mycotoxins that are hard to tackle, storage mycotoxins can be easily avoided if the maize is stored under appropriate conditions. For achieving this, the moisture content has to first be reduced to a storable level, keeping in mind that the drying process should be as gentle and homogeneous as possible to avoid any product quality deterioration. The last moisture percentages can be easily eliminated using a grain chiller, improving both the product quality, as well as the drying and cooling efficiency. If maize is kept at low temperatures and storable moisture levels, the risk of development of fungal mold is nil and thus contamination with storage mycotoxins can be completely avoided. Apart from this, improvements in maize storage include but are not limited to: reduced corn cracks and thus higher grit yield, higher starch content, less dry matter loss, less shrinkage and improved feed pellet quality.


Wheat cooling

Wheat in one of the most important crops in the world and used in human consumption all over the planet. It is typically stored for longer periods of time, often reaching several years of storage before it is milled and thus proper storage conditions are of utmost importance to maintain the product quality. Cooling wheat to below 14°C not only eradicates infestation, baking, mold and mycotoxin issues, but it also minimizes dry matter losses caused by respiration and maintains the harvest freshness without changes in colour and odour. It further enhances the yield as well as milling performance and- safeguards the baking properties of the resulting wheat flour, making sure the end consumer can enjoy best quality bread. As wheat is a good insulator, once cooled, the bulk will remain cool for a long period of time.


Cooling of malting barley

Barley is of utmost importance for the beer brewing process. The most important concern in this regards is the germinability of the barley, as it has to be partially germinated in the malting process. Poor germination rates lead to poor quality beer. Several studies have shown, that the dormancy of barley isn’t negatively influenced when the grain is chilled, but the germinability can be enhanced significantly, it is thus recommended to cool malting barley. Cooling further prevents the growth of fungal mold and subsequent mycotoxin formation and hence prevents excessive foaming during the brewing process as seen when mycotoxin contaminated malting barley is used.


Cooling of oil seeds

Oil seeds have to be stored at very low moisture levels, because of their high fat content. The high fat content makes them prone to oxidation processes which lead to a much faster metabolism and hence self-heating when compared to other crops. In order to maintain best product quality and prevent oil seeds from oxidation and subsequent rancidity, it is highly recommended to cool them using a grain chiller.


Feed pellet cooling

During pellet production, ambient air doesn’t suffice to achieve a complete cooling of the pellet core. Insufficient cooling leads to an increase in stress cracks and makes the feed pellet prone to having a powdery surface. The use of a chiller makes sure that the pellets are cooled to the core and the pellet is hardened. The resulting end product is easy to transport and ideally apt for bird and animal consumption.


Pulses cooling

Pulses are one of the richest sources of protein and other nutritional values and a great replacement for animal proteins. The most important quality measures are yield, colour (pulses can oxidize, and lose colour and grade), aroma (toordall), starch content and fluffiness (oriddall). The moisture content of pulses varies from 16% to 20% and for safe storage it has to be dried below 14%. Even after the moisture of the grain is reduced to safe storage levels, the risk of insect infestation remains due to typically high ambient temperatures in pulses producing regions. By using a grain chiller, the grains can be stored with a moisture content of up to 16%, reducing the moisture during the cooling process to a safe level of 14% and below and at the same time saving on energy costs for both drying and cooling. Cooling pulses eliminates the need to worry about insect infestation, discoloration and dry matter losses and leads to high milling performance as well as conservation of harvest freshness, aroma, nutritional values and fluffiness.


Cooling of seeds

With farmers aiming at higher and higher yields, the quality of seeds is more important than ever. Seeds are produced in much lower quantities and achieve much higher prices than regular grains, because there can’t be any compromise on the seed quality. The most important characteristic of seeds is their germinability, the lower the germinability, the lower the yield on the field! It has been shown in several studies, that chilling of seeds doesn’t negatively influence the dormancy, but improves the germinability significantly. Apart from all the other advantages in product quality that come along when cooling seeds, it is thus strongly recommended to use a grain chiller in seed storage.

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