Microwave Dielectric Properties of Fresh Fruits and Vegetables

ABSTRACT THE dielectric properties of some fresh fruits and veg-etables were measured at 2.45 GHz and 23 °C by the short-circuited coaxial-line technique, and data are presented for the dielectric constant and loss factor of several peach cultivars, two sweet potato cultivars and single cultivars of potato, apple, cantaloupe, and carrot. With the measurement techniques used, no differences in dielectric properties were distinguishable between mature green and full-ripe peaches or between cured sweet potatoes and those that had been subjected to chill-ing injury after curing for induction of the hardcore con-dition. The dielectric constant was correlated with moisture content and also appeared to be influenced by tissue density. No correlation was observed between dielectric properties and soluble solids as measured by a refractometer. For better assessment of the usefulness of electromagnetic fields for measurement of fruit and vegetable quality, study of the frequency dependence of the dielectric properties of such materials over a wide range of frequencies is recommended.