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Cereals and legumes are invaluable resources, as they represent the raw materials of many foods and beverages. Cereals are also largely used as livestock feeds, thus indirectly influencing the quality of dairy products and meat. Because of their key role in human nutrition and well-being, the safety and quality of these agri-food materials are extremely important topics in food science. In this regard, moisture content is one of the ultimate factors influencing the quality, safety and price of the final food product; hence, it is crucial to monitor water content of materials in the food production line. Starting from these considerations, this paper describes the use of time domain reflectometry (TDR) for both in-line and off-line moisture content sensing of agrifood materials. In particular, after a brief description of the basic principles of TDR, two representative application cases for moisture content measurements of agri-food materials are reported and commented on.

In this work, the performance of three time domain reflectometry (TDR) instruments (with different hardware architectures, specifications and costs) is comparatively assessed. The goal is to evaluate the performance of low-cost TDR instrumentation, in view of the development of a completely permanent TDR-based monitoring solution, wherein the costs of the instrument is so low, that it can be left on-site, even unguarded, and controlled remotely. Without losing generality, the applications considered for the comparative experiments are the TDR-based detection of leaks in underground pipes and, more in general, of soil water content variations. For this reason, both laboratory and in-the-field experiments are carried out by comparatively using three TDR instruments, in conjunction with wire-like sensing elements (SEs).

In this work, time domain reflectometry (TDR) is used in conjunction with an innovative type of low-cost, wirelike diffused sensor for diffused soil water content monitoring in agriculture. Thanks to its wire-like configuration, these passive, maintenance-free sensors can be rolled out and buried along the perimeter/path to be monitored (for example, along a row of plants/trees). A single sensor can be long up to 150 meters, and several sensors can be simultaneously installed in a large area, thus creating a diffused sensor network which can be controlled through a single measurement instrument. To assess the practical feasibility of the proposed TDR-based system, a practical experiment was carried out by employing a bifilar, wire-like sensing element (SE) for monitoring soil water content in a watermelon cultivation. For comparative purposes, also in view of continuous remote monitoring, measurements were carried out through three TDR instruments with different specifications and costs.