Healthy flour and semolina can only be made from healthy grain.

Grain is constantly under attack. The weather tries to damage it, insects try to consume it and lay their eggs in it and birds and rodents eat it and leave their evidence behind.

Bacteria, fungus and mildew try to live on it too.

Grain is a precious commodity. We should be doing more to protect it and more to ensure that end consumers can enjoy a consistently healthy product.

Global spoilage

The United Nations estimates that the grain lost to spoilage worldwide is more than 20 percent. If we estimate that the world wheat harvest is about 650 million metric tonnes, that"s 130 million tonnes of post-harvest losses. Can a world with an ever growing population afford to be losing that much grain every year?

The majority of this loss is due to insect activity and mildew growth.

Therefore, we need better storage methods for grain, better preservation methods and better cleaning systems.

It"s a fact that insects adore broken grain and grain with a high amount of screenings or dockage. Research in the 1960s showed that confused flour beetle survival in stored, eight percent moisture wheat was nearly 95 percent after 12 weeks, yet storing that same wheat with the screenings removed reduced the beetle"s survival rate to only five percent.

Things we can do

What can we do to minimize grain losses?

First, we need to consider the way that the grain is stored. It"s important to select the right type of equipment. Flat bottom silos are a good solution for seasonal storage, but they don"t suit a production environment where consistent discharge or a first in-first out (FIFO) system is required.

If we are going to build new silos, should they be sealable in case we need to carry out fumigation? Australia, for example, has adopted specific silo standards to be used for fumigation and these standards include minimum construction requirements and the need for frequent pressure testing.

Grain handling produces dust and broken grain. Insects thrive on this broken grain; therefore, we must carefully design the site layout to take account of truck movements, especially with regard to segregation from pedestrian movements, the size/type of trucks and method of discharge.

We must carefully think about minimizing conveyor lengths and elevator heights because these cause a lot of grain breakage, use high amounts of energy, and can have high maintenance costs.

Petkus has developed new elevating and conveying machines and options to significantly reduce grain breakage.

Bucket elevators can now be supplied with a twin-head pulley design that changes the angle at which the grain is discharged from the bucket. The discharge is more by gravity rather than centrifugal force and therefore allows a much slower belt speed to be used without the need for special buckets.

The Petkus" RF Troughed-chain Conveyors feature a round bottom with plastic scrapers and a slow chain speed for gentle handling of grain over long horisontal distances. The round bottom also makes the conveyors self-cleaning.

Thorough cleaning

Within the flour milling process, we thoroughly clean the grain before milling, but should we not be taking more steps at the grain storage and mill intake stage to prevent this insect degradation?

Mechanical cleaning systems can efficiently remove screenings/dockage and dust.

At truck intake, we can use fans and filter walls to trap dust, helping to remove this unwanted material from the grain and improve the workplace for intake system operators.

The Petkus SM30 machine is a new take on the conventional Milling Separator. By splitting the inlet feed 50/50 and using twin coarse and fine separation decks in parallel, the capacity is doubled without any appreciable increase in aspiration system costs and power usage.

The SM30 cleaner can reduce the footprint needed for intake/pre-cleaning equipment.

Further, the machine"s galvanised construction lends itself better to silo installation areas compared to painted machines.

For a more thorough pre-cleaning, a higher-capacity cleaner, such as the "V" cleaner, features pre-aspiration, post-aspiration and six screen layers. Its rugged, all-metal construction ensures high strength and long life. It also removes the risk of contamination coming from the timber that has typically been used in the construction of these types of cleaners.

The unique top screen area uses a motorised scraper assembly. The scraper is able to positively remove foreign material from the screen much more effectively than ball cleaners, especially on this higher contamination level intake application.

The scraper ensures that the grain moves correctly on the top screen. Grain that moves too fast is retarded and grain that moves too slowly is pushed along – allowing for much more efficient use out of the top scalping screen.

The "No Weld" design of Petkus machines allows the greater part of the manufacturing process to be automated and the machine assembly area to be extremely clean, since no welding or grinding dust is present in the factory.


Even with all the preservation and cleaning methods in place, we may still encounter grain that is effected by Fusarium or has unacceptable DON content. For these problems, the Roeber OptoSelector has the ability to perform optical sorting based on RGB colour, geometric (shape) sorting and NIR simultaneously. Further, a new version of the machine is capable of RGB transmission sorting and able to analysis the image of light having passed through the kernels.

It"s making it possible to detect dent/field corn in popcorn, soft wheat in durum wheat and other hidden properties where the external colours and shape of the grain and defects are identical.


Wheat is a precious commodity, with unstable conditions such as those that we see in around the world, changing weather patterns and ever-growing demands in Asia, we need to reduce the wheat losses that occur post-harvest and better manage the supply chain.

Using good technical solutions, modern equipment and process can help us drive towards this goal.

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by Roger Cook, Technology Manager - Asia & Australia, Petkus Technologie GmbH, Germany

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