The radio frequency identification (RFID) of food items improves production process efficiency as well as optimises the management of the monitoring and the logistics along the production chain (Barge et al., 2014). Moreover, interest in UHF RFID tags adoption is growing in particular applications such as anti-counterfeiting systems. The readability of passive UHF RFID tags is well known to be critical when applied to products at high water content. Nevertheless, the effect on readability of solutions of water and other organic (e.g. ethanol, sugars, organic acids) or inorganic (salts) compounds, which are typical of food and beverage composition, has not yet been studied. Furthermore, as in the case of beverages that must be chilled for their conservation (i.e. fruit juice, fresh milk and other pasteurised beverages), the temperature can compromise tag readability. RFID systems efficiency may also be affected by tag-to-reader antenna misalignment, which often occurs for cylindrical section containers.
Experimentation has been conducted to evaluate the effect of temperature, different solute type and tag orientation on the readability of a commercial passive RFID UHF tag (Lab Id UH100) applied to a HDPE (High- density polyethylene) bottle. To compare readability, the minimum transmitted power output that allows the tag-backscattered signal (Pmin) to be acquired by the reader was measured in standard controlled conditions. It was observed that solution temperature strongly affected the readability of passive UHF RFID labels. The correlation between temperature and readability was observed being positive or negative depending on the adopted solute type. In particular, an improvement in readability was detected for deionized water, sucrose and ethanol solutions when temperature was increased from 4°C to 25°C. Readability decreased for citric acid and NaCl solutions in the same temperature range.
Reading performance was highly influenced by bottle rotation along the vertical axis, which caused both the misalignment of the tag-to-reader mutual orientation and the radio wave reflection and absorption phenomena due to the presence of the considered solutions in different positions.