Breads are prone to rapid microbial spoilage, particularly mold growth. In order to develop in-package pasteurization treatments based oil radio frequency or microwave energy, a combined open-ended coaxial probe and mixture equation method was used to obtain bread dielectric properties over the frequency range of 1-1800 MHz and the temperature range of 25 degrees C-85 degrees C. influences of frequency, moisture content and temperature on bread dielectric properties were analyzed. The Lichtenecker Equation (LE) Was suited for calculating dielectric constant, and the Landau and Lifshitz, Looyenga Equation (LLLE) for dielectric loss factor of bread. Penetrations of both RF and microwave energies decrease with increasing temperature and Moisture content. Overall. RF energy has several times the penetration in white bread than microwave energy. (C) 2009 Elsevier Ltd. All rights reserved.