DIFFUSION OF BEET DYE DURING ELECTRICAL AND CONVENTIONAL HEATING AT STEADY‐STATE TEMPERATURE¹

Abstract

Ohmic heating has been shown to alter mass transfer properties of fruit and vegetable tissue. Diffusion of beet dye from beetroot tissue into a fluid was studied during conventional and ohmic heating as a function of steady‐state temperature. The volume of beet dye diffusing into solution during ohmic heating was enhanced with respect to conventional heating at 42C and 58C, but not at 72C. This can be explained by examining the differences in electrical conductivity of beet tissue at these temperatures during conventional and ohmic heating. At 42 and 58C, the electrical conductivity of beet tissue heated ohmically is higher than the electrical conductivity of beet tissue heated conventionally. At 72C, the electrical conductivities of beet tissue during conventional and ohmic heating are equal. The extent of diffusion in the ohmic case is also positively correlated with applied voltage. These results suggest that food processes involving mass transfer can be enhanced by choosing conditions in which the electrical conductivity of a sample under ohmic conditions is maximized.

Enhanced Extraction from Solid Foods and Biosuspensions by Pulsed Electrical Energy

“…However, the effects of OH are not purely thermal. Several researches have noted that OH also induces electropermeabilization [48,51,52,65,76,86]. It was shown that even mild OH electrical treatments permitted enhanced diffusion in vegetable tissues [53].…”

The Use of Electric Fields for Edible Coatings and Films Development and Production: A Review

“…Scanning electronic microscopy (SEM) and X-ray diffraction (XRD) are frequently used to characterize edible films' structure [5,50]. SEM may be used to evaluate film homogeneity, layer structure, pores and cracks, surface smoothness and thickness, while XRD is mainly used to evaluate the degree of crystallinity of the films.…”

Low-frequency dielectric changes in cellular food material from ohmic heating: Effect of end point temperature

“…Diffusion is enhanced, electrical conductivity changes are more linear during heating, and moisture migrates more easily out of the tissue (Halden, de Alwis, & Fryer, 1990;Imai, Uemura, Ishida, Yoshizaki, & Noguchi, 1995;Lima, Heskitt, & Sastry, 2001;Schreier, Reid, & Fryer., 1993). Thus, ohmic pretreatment has been found useful in drying and juice extraction processes (Wang & Sastry, 1998), and in sugar extraction from beets (Fedorenchenko et al, 1983).…”