Ripening and development of chilling injury in persimmon fruit: An electrical impedance study

Abstract

Abstract Electrical impedance spectroscopy was used to follow ripening and chilling injury development in persimmon fruit ( Dyospyros kaki L. ‘Fuyu'). Tissue resistance and reactance were measured at frequencies between 50 Hz and 1 MHz, and then fitted to an electrical model. Fruit responses to both ripening at 20°C and storage in modified atmosphere at 7°C were distinct and easily detected using electrical impedance spectroscopy. Plots of reactance against resistance at each series of frequencies traced a semicircular arc. During ripening, the arcs dilated between Days 1 and 21, then contracted, until at Day 35 they were smaller than at Day 1. Electrical modelling indicated that the dilation occurred as a result of a 43, 115, and 17% increase in resistance R \ (cell wall resistance), R 2 (cytoplasm resistance), and R 4 (vacuole resistance), respectively. After 35 days of ripening, R 1 was 39% lower and C 3 (membrane capacitance) was 19% higher than at Day 1. Chilling injury developed with increasing time at 7°C in modified atmosphere storage (MA), until severe symptoms were observed after 5 weeks. Chill‐injured fruit differed from other fruit in that R 2 was significantly lower upon removal from storage, although it rapidly increased when fruit were transferred to 20°C for ripening. These results are discussed in relation to the physiological changes that occur during ripening and development of chilling injury in persimmon.