Accurate to the point - microwave-based moisture measurement increases productivity.

Fast and accurate measurement of the moisture content in food can save time and money. Too high or too low moisture is undesirable. This often leads to loss of quality and makes further processing of the intermediate product more difficult or even impossible. If the moisture content is known, drying times can be optimized. Improved quality and longer shelf life are the result.

To determine the moisture content, Tews Elektronik, Hamburg, has developed measuring instruments that deliver accurate measured values reliably within seconds. With up to 4,000 measurements per second, the instruments enable the precise moisture measurement of the laboratory to be integrated into the process control in real time.

The special feature of this technology is its independence from colour, density, grain size and surface influences of the product to be measured. In contrast to the so-called near infrared method, which measures the moisture only at the surface, the instruments also measure the core moisture inside the material to be measured. This also makes it possible to determine the moisture values of products that only dry superficially in the air or cannot be measured at all with other conventional methods.

The measurement method is based on microwave resonance. As soon as the material passes through the field of the microwave sensor, its resonance properties change depending on the water content. A single configuration of the system is all it takes to ensure continuous and reliable operation.

Today, the patented microwave resonance method is used in process and laboratory applications in many industries. The samples are neither damaged nor heated by the microwave measurement. Another special feature is that the samples do not have to be specially prepared for the measurement, but can be fed into the sensor in their original state, for example. Thus, the samples are available for further measurements or as a reserve sample. This distinguishes the microwave resonance method significantly from other measuring methods such as drying in the oven, in which the moisture content is determined by weight loss. In this case, the samples have to be prepared with great effort, in the case of cereals by grinding. Other measuring methods are based on chemical processes and require a very careful approach. In addition, both methods require a waiting period - often many hours - before the results are available, while microwave moisture meters make the measurement results available immediately. For more than 25 years, Tews instruments have been used in all areas of the food industry, both process and laboratory. These instruments are ideal for measuring soy flour, pasta, pastries, cereals, milk powder, starch, marzipan, oilseeds and pet food. Moisture values for cocoa or coffee beans can also be determined quickly and easily. This already starts with the delivery, where the green beans are tested for their input moisture. Later in the process, the sensors are used in the roasting process or shortly afterwards, and at the end they can also be used for the ground product. Through continuous research and further development of the microwave resonance method, the measurable moisture range is permanently increased, which means that the moisture content of grain, such as wheat, oats or rice, can now also be measured in silos.

Knowing the moisture content throughout the production process is a key to quality and cost control. Accurate continuous moisture measurement can optimize drying times, resulting in energy savings. At the same time, shorter drying times increase productivity. An optimum water content means longer shelf life and better processability of the intermediate or end product, and thus less waste. The simple operation and low maintenance requirements of the equipment also contribute to increased efficiency.

Author: Wolf-Dieter Stechmann, Food Technology

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