Determination of cell disintegration index
The conductivity–frequency spectra of treated and control samples of paprika were determined (Angersbach, Heinz & Knorr, 1999, Knorr & Angersbach, 1998 and Angersbach & Knorr, 1997). The cell integration index (Zp) was defined as:
equation(1)
Where b=Kh/K′h; Kl and K′l are the electrical conductivity of control and treated samples at low frequency field (1–5 kHz) and Kh and K′h are the electrical conductivities of control and treated samples in a high frequency field (3–50 MHz). The cell disintegration index characterises the proportion of cells with highly permeable cell walls. Zp is between 0 and 1, corresponding to 100% intact cells and total cell disintegration, respectively. The conductivity for control and treated samples was determined with impedance measurement equipment (Electronic Manufacture Company, Mahlsdorf, Germany) between parallel disc electrodes (9.7 mm diameter) spaced 10 mm apart. The phase voltages were each of equal amplitude (typically between 1 and 5 V peak-to-peak) and the frequency changed in the range from 3 kHz to 50 MHz.