91C-9 |
Extraction from leafy materials using moderate electric fields: Effects of field strength and frequency |
I. SENSOY, Food Agricultural and Biological Engineering, The Ohio State University, 590 Woody Hayes Dr., Columbus, OH 43210 and S. K. Sastry. During Moderate Electric Field (MEF) processing, a voltage applied across a food material may affect the permeability of cell membranes. It is known that high electric field can cause either reversible or irreversible rupture of cell membrane. In this research, effect of MEF processing on permeability was studied. Effects of frequency and electric field strength were investigated. Cellular structure was investigated by transmission electron microscope (TEM). Fermented black tea leaves, fresh or dry mint leaves were placed in tea bags or cut in 1 cm2 squares depending on the experiment, and immersed in an aqueous fluid medium. Control samples were heated on a hot plate. Moderate electric field treatments were conducted by applying a voltage across electrodes immersed in opposite sides of the beaker. Extraction rate of control and MEF processed samples were compared. Effects of electric field strength and frequency on extraction rate of MEF processed samples were investigated. Control and MEF treated fresh mint leaf samples heated to 50°C were analyzed under TEM. MEF processing significantly increased the extraction yield for fresh mint leaves due to additional electric field effect during heating. Dried mint leaves and fermented black tea leaves were not affected by the treatment type. Low frequency resulted in higher extraction rates for fresh mint leaves. Electric field strength study showed that electrical breakdown is achieved even at low electric field strengths due to high temperatures, result of ohmic heating. MEF treatment shows potential to be used as an alternative to conventional heating for extraction from cellular materials.
Session 91C, Food Engineering: Food process engineering
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