Sensing Moisture Content in Dates by RF Impedance Measurements

The moisture contents of the flesh and pits of Deglet Noor dates, with flesh moisture contents ranging from 13 to 30%, wet basis, were determined by vacuum oven drying. Impedance measurements at frequencies of 1 and 5 MHz were made on a parallel-plate capacitor with individual whole dates and pitted dates held between the capacitor plates. Moisture content of the dates was related to the impedance measurements by a stepwise multiple regression technique. Linear single-variable models were developed that provide an instantaneous and nondestructive determination of moisture content with standard errors of about 1% moisture content. The technique is recommended for potential development and application in reducing the skilled labor requirements for manual sorting and grading of dates.