Miller Magazine Issue: 132 December 2020

67 ARTICLE MILLER / december 2020 extraction of the grains by another mechanical process called threshing. Depending on the destination of the yield, the crops need harvesting at precise moisture. For example, harvesting and threshing grains when it is too dry (water content below 20% – 25%) can lead to loss, waste, and breakage of material. Contrary to that, if crops are too wet, it is possible to get mechanical issues requiring additional adjustment of the harvesting equipment. Wet crops will also limit the weight capacity of the machinery and cause problems with the threshing action. The water content of the yield can be measured inline directly inside the combine harvester to calculate the dry weight as well as provide additional information about spatial variability in the field. Depending on the location and the weather, the first 48h are crucial for the yield, as mycotoxins can contami- nate the product before the storage and drying operati- ons. Knowing the moisture during the harvest will also allow the farmer to plan quickly ahead. STORAGE AND DRYING After the previous operations, the crop needs to be stored and preserved accordingly to prevent mycotoxins, spoilage, or heat spots. These often give problems that are directly related to the moisture contents of the grain. Monitoring moisture during storage is fundamental to be able to regulate the storage operations and to react timely to problems. Drying is a common practice to store grains safely, and it is a delicate process to reach the per- fect moisture. By missing the target, the crop is still prone to mycotoxins and spoilage, on the other hand, over-dr- ying is not just an expensive waste of energy but can cause damage and breakage to the grain’s skin, making it prone to mycotoxins and insect attacks. Excessive drying can also cause the grains to sh- rink in size, causing yield loss. The material ente- ring the drier has variable water content, and this makes it challenging to regulate the amount of time the material needs to be exposed to the heat or to regulate the temperature. In this process, the inline moisture control is used to automate the dr- yer to save money and improve the quality. CONDITIONING After drying, depending on the material and sys- tem requirements, it may be necessary to reintro- duce water into the product by conditioning. This process can be done before the grinding mill and before pelleting operations. Depending on the fi- nal application, the conditioning can also heat the material to kill germs, to cook ingredients, and to gelatinate starch. In the same way that moisture control enhances the dr- ying phase, it also improves the conditioning process by monitoring the target moisture to react timely to changes in the input material. GRINDING Grinding is one of the most energy-consuming trans- formations in many food processes. Through mechani- cal action, it reduces the size of food materials such as grains, seeds, fruits, and many more to achieve different chemical and microbiological stability.Results vary based on machines and methods used, as well as toughness and moisture of the material processed. The toughness is the ability of a material to resist bre- akage; therefore, tougher material will need more me- chanical energy to be reduced in size. The plasticity or ductility of a material determines the amount of energy absorbed before breaking down as well as the final size. More plastic or ductile material will need more energy to break, but it will maintain a more regular final shape. In contrast, less plastic or ductile material will shatter into finer and irregular shards like particles. The elasticity of the material is defined by its water content: therefore, by controlling the moisture of the material, it is possible to determine the energy consump- tion of the process, the final size of the powder particles, and the product yield and loss. For these reasons, the initial moisture of many food materials is the most important element to regulate befo- re the grinding process. TRANSPORT AND FLOWABILITY After the grinding process, the moisture remains very important as it determines the flowability of the particles