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DIELECTRIC PROPERTIES OF FUJI APPLES FROM 10 TO 4500 MHZ DURING STORAGE
Author(s) -
GUO WENCHUAN,
ZHU XINHUA,
YUE RONG,
LIU HUI,
LIU YI
Publication year - 2011
Publication title -
journal of food processing and preservation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.511
H-Index - 48
eISSN - 1745-4549
pISSN - 0145-8892
DOI - 10.1111/j.1745-4549.2011.00541.x
Subject(s) - postharvest , flesh , dielectric , water content , chemistry , penetration depth , moisture , composite material , materials science , horticulture , food science , optoelectronics , optics , biology , physics , geotechnical engineering , engineering
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. PRACTICAL APPLICATIONS Information on dielectric properties of apples could be useful in developing thermal treatments for postharvest insect control based on radio frequency (RF) and microwave (MW) energy, and non‐destructive method to detect fruit quality during storage. Dielectric properties data could be used to estimate the heating rates of apple samples and design the treatment bed thickness in RF and MW systems. However, the limited penetrations at frequency higher than 3,000 MHz and weak correlations between permittivities and quality indices suggest that sensing apple quality from their dielectric properties might not be practical under experimental conditions used in the present study.