Law of dielectric parameters and texture properties for grape during cold storage

Dielectric parameters were non-destructively measured over frequency range from 0.1 kHz to 3980 kHz with a parallel-plate copper electrode and HIOKI 3532-50 LCR meter in order to study the law of dielectric and texture parameters of Red Globe grape during cold storage at 0℃. Firmness, chewiness, springiness and adhesiveness of grape were measured as texture attributes for correlation with the dielectric properties. The optimum frequency for dielectric properties test was identified and the regression equation was built. The results showed that fruit impedance, resistance, inductance and reactance decreased gradually by exponential form with the increase of frequency and 0.1 kHz was the optimum frequency for dielectric properties test. At the optimum test frequency, impedance, resistance, inductance and reactance decreased linealy with the extension of storage time. At the same time, firmness and chewiness decreased gradually with the time went on, springiness and the absolute value of adhesiveness went up contrarily. At 0.1 kHz frequency, the high correlation was found between dielectric and texture parameters, such as reactance with texture parameters (P<0.05). At last, the regression equation was built for dielectric and texture parameters, reactance could be used as sensitive dielectric parameter marking variations of texture properties.