Old and new challenges on grain and flour QA systems

12 February 20218 min reading

Vasilis Sotiroudas

Vasilis Sotiroudas Food Safety Specialist

Easy access to sufficient amounts of safe and nutritious food makes a major contribution in sustaining life and promoting good health. Unsafe, risky food ingredients can cause hundreds of diseases. Food can be contaminated at any point of the production, distribution and preparation processes and everyone along the production chain, from producer to consumer, has a role to play in food safety. Quality Assurance systems (QA) are in place along the supply chain to reassure that each ingredient is safe and traceable.


Wheat is one of the most important type of crops in the world. Its ease of adaptation to the soil is the main factor for its spread to several areas of the world. According to FAO’s report, the global wheat trade in 2017 reached 754.8 million tons. Russia exports of wheat amounted to 30 million tons, US 26.5 million tons, Europe 25 million tons (

Proper cultivation of grain includes the use of Good Agricultural Practices (GMPs) to minimize contamination in the field, during harvest, drying and transport to storage. Proper sampling and testing of the grain as it leaves the field and enters the supply chain, ensures that standards for heavy metals, agro-chemicals and mycotoxins are observed. Moreover, grain is tested for foreign materials and microbiological hazards.

Food Safety

Reaching the first storage area, GMPs and HACCP plans are in place to ensure that the grain is not contaminated during transport, storage and milling. Milled grain shall be stored in cool and dry places away from hazards and infestations. Finally, the consumer must be aware that flour may contain pathogens and shall be cooked properly.

A thorough traceability system, monitors grain and flour along the chain, proving that quality assurance systems are designed with precision and are followed in detail by everyone involved.


In the science of quality assurance, everything is about risk! The hazards are present, the preventive measures are taken, sampling and inspection are applied. Everything is related to how effectively was the preventive measure designed, how thoroughly it is applied and how serious is the threat. All these probabilities produce the level of risk. For the purpose of this article, we measure risk at 4 levels: no risk, low, medium and high. The following table shows the expected hazards and their risk, in the grain-to-flour supply chain.

In the following paragraphs, we analyze the supply chain points with a level or risk.


The quality of irrigation water and the respect to good practices, keep the risk down for contaminants that may come with water and for pesticide residues. In addition to that, the weather conditions can be related to the development of fungi on the plants and even to the formation of mycotoxins.

wheat trade

There are several cases where irrigation water was contaminated by sewage water and affected rice which is growing in the water. Or cases that the weather caused the development of Aspergillus flavus on the corn plants and the harvested crop showed serious concentration of aflatoxin.


The harvesters and the farm lorries are usually left at the end of the season uncleaned. They become a source of infestation by stored product insects (mainly of the Sitophilus species) for the next crop. This incident is happening so often and so regularly around the world that it has become the main reason why stored product insects find their way so easily in the new crop.


The farmer’s silos and warehouses are in many cases the first storage assets in the supply chain. There are two risks related to this storage. The first one is the development of mold which can alter the organoleptic characteristics of the grain giving a bad odor and forming crumbles of kernels stuck together by the forming of mycelia. Mold develop when moisture is over 15%. This can happen when a drier is not working properly or when rainwater finds its way into the grain. With high moisture, a crust is formed on the grain, usually on the surface. Natural aeration is then blocked and temperature rises due to poor aeration and enzyme activity. Insects love elevated temperatures and will multiply rapidly when they are present causing further damaging. Development of mold can lead to the production of mycotoxins which are carcinogens, making the grain unfit for consumption by humans or animals. New technologies have made it easier to monitor stored grain. Wireless sensors like those of monitor several parameters and alert the user when the condition becomes unsafe. The best parameter to monitor to avoid spoilage is CO2. The concentration of this gas is seriously increased at the beginning of mold development and sensors can pick up the increase even when positioned many meters away from the hot spot. On the contrary, system that are monitoring only temperature and moisture, are usually unable to detect spoilage at an early stage.

grain silos

The second risk in the farm silos or warehouses is the wrong use of pesticides like contact insecticides which may lead to residues on the grain. Good practices and following the product label is always the solution. The application of contact insecticides on grain is allowed only through automatic pumps and very few products are registered for this use.


Larger storage compartments like country elevators or port silos are usually having similar risks to the farmer silos analyzed in the previous paragraph. An additional risk is the mixing of grains or oil seeds on the lines and in the silos. Grains contain gluten which is registered as an allergen. Soy seeds contain Soy protein which is another allergen. Allergens shall be declared on the final product label and having a mixing of seed in a silo would give a risk that is not expected further down the supply chain. Allergens are a threat to human lives and several cases of product recalls are registered every year due to undeclared allergens found. Even the dust of grains sitting in the same warehouse could turn an allergen test to positive. Detailed traceability and thorough cleaning are the best preventive measures. A modern automated traceability system is shown in the next graph, based on silo level sensors and a third-party web platform.

Soy in wheat flour, soy in corn, and wheat in oats are a few examples of food allergen cross-contamination risks. The validation of a well-designed traceability system depends on allergen detection and quantification methods. An automated traceability system is necessary not only to comply with food labeling requirements, but also to prevent costly product recalls, improve consumer protection plans, ensure consumer’s confidence, and protect the brand name of the manufacturer.


A mill has all the potential food safety risks. The water that comes in contact with grain, may carry microbiological and chemical hazards. Only potable water shall be available in a mill. Mold and insects may develop in the grain silos, especially during long storage. Modern silo monitoring systems are necessary. The mills are usually vulnerable to insect cross infestation as stored product insects can move between silos, machinery and silos and contaminate grain, ingredients and flour. A combination of precision fumigation techniques shall be applied. Heat treatment is the best option for empty bins and production areas while phopshine, CO2 or low oxygen may be used with grain and flour.

Insect eggs are not always killed by entoleters. Semolina and whole grain flours are more vulnerable to insects.


After the flour is packed, it is vulnerable only to insects. With the use of a sealed package and modified atmosphere even insects cannot enter or survive. With the normal package though, it remains exposed to insects, although in most cases the insect eggs are already in the flour, surviving the milling process. Wholesale warehouses and retail shelves shall have in place modern Pest Management systems to detect insect presence early and prevent infestation. Our pantry too! We must thoroughly clean our houses and inspect for insects that may arrive with product 1 and infest all of our reservoir. Especially in the months of Covid-19 when our anxiety fills our shelves up, we shall inspect for stored product insects, more often.


Since 2009 there have been several outbreaks of foodborne illness involving raw flour or raw flour-containing products like cake mixes and cookie dough. These have resulted in 168 known illnesses and 20 hospitalizations in USA. Uncooked flour can carry a variety of disease-causing germs, including E. coli. An outbreak of E. coli in USA traced to raw flour made 63 people sick in 2016.

The use of Good Processes along the supply chain, minimize the contamination sources. However, grain will always grow in the fields and will always be exposed to microorganisms. The pathogens may find their way to flour but as its water activity is very low, they will never multiply. Adding water and other materials on flour, allow the existing pathogens to develop. Baking will kill the pathogens but if we eat raw or undercooked dough, the risk is high.

Designing and maintaining complete quality and safety assurance systems is not an easy task. Using IoT and new technologies saves a lot of energy and moves the weight off the people shoulders to sensors and AI algorithms that simulate conditions and send alerts, much earlier than a human nose could detect a strange odor!

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