Effect of short time heating on the mechanical fracture and electrical impedance properties of spinach (Spinacia oleracea L.)

We evaluated the mechanical properties and electrical impedance data of spinach after short time heating. The mechanical fracture properties of samples heated for 40 s significantly differed from those of the non-treated samples. A circular arc of the Cole-Cole plot obtained from the impedance data shrunk after heating for 10 s. Similarity of the circular arcs, i.e. non-uniformity in the electrical characteristics, changed after heating for 30 s. After heating, extracellular resistance values were decreased from 650 to 16 k Omega, and cell membrane capacitance values were decreased from 13 to 0.28 nF. These changes could be evaluated simply by using the length of the coordinate at the top of the circular arc from the origin, and these occurred earlier and were greater in magnitude than those in the fracture properties were. These electrical properties could be an index for the early detection of changes in the fracture properties of samples. (C) 2016 Elsevier Ltd. All rights reserved.