DIELECTRIC PROPERTIES OF FUJI APPLES FROM 10 TO 4500 MHZ DURING STORAGE

Dielectric constants and loss factors of apples with skin (skin on) and without skin (skin off), and flesh juice of Fuji cultivar during 21-week storage at 5C were measured at a 3-week interval and 24C from 10 to 4,500 MHz. The firmness and moisture content of the flesh, and soluble solids content (SSC), pH and direct current conductivity of the juice were also measured. The pH increased and firmness decreased with storage time. There was no obvious change or trend in moisture content, SSC, conductivity and permittivities during storage. The depths of penetration in skin-on and skin-off apples, and apple juice decreased with increased frequency. Weak correlation between apple permittivities and internal qualities and limited penetration depth shows that sensing apple internal qualities from permittivities of skin-on apple, skin-off apple and apple juice is difficult.