Determination of physicochemical quality of bruised apple using dielectric properties

In this study, apples were damaged by dropping from different heights(40、60、80、100 and 120 cm) to the marble ground and stored at 1 °C and then the quality and dielectric parameters of the apples were measured after different storage durations (1、5、9、13、17、21 and 25 d). The results showed that the firmness, density, titratable acidity (TA), vitamin C and moisture content decreased, the browning degree and total soluble solid/titratable acidity(TSS/TA) increased, the total soluble solid (TSS) exhibited a increasing–decreasing trend with the storage time increased. The higher the drop height of the apples, the lower the firmness, density, TSS, TA, vitamin C and moisture content and the greater the browning degree and TSS/TA. A principal component analysis showed that two principle components could represent the dielectric parameters of the damaged fruit, and the accumulated variance contribution rate was more than 80%. At the characteristic frequency, which was selected using a gray correlation analysis, the principle components predicted the quality parameters and established the prediction models for quality parameters. The determination coefficients of prediction equation about density, TSS, TA, vitamin C and moisture content were all greater than 0.6, it was indicated that the prediction results of these quality parameters were better. The results are expected to provide a reference for the rapid evaluation of quality changes for damaged fruit by using electrical properties.