Analysis of microwave heating uniformity in berry puree: From electromagnetic-wave dissipation to heat and mass transfer

To understand the non-uniformity of microwave heating, berry puree selected as representative material with high moisture content, movement simulation and beach experiments were employed to analyze the non-uniformity formation and evolution in the blueberry puree loaded in a rectangular container (BLRC) under microwave heating. The results showed that the coupling process via microwave dissipation and heat & mass transfer dominates the uniformity of microwave heating BLRC. The decisively heating modes of microwave dissipation are transverse electric wave and transverse magnetic wave, whose features of microwave dissipation dominate the heat and mass transfer process in BLRC as three distinct stages of temperature changes, including slow elevation then stabilization followed by quick increase. Thermal accumulation, thermal conduction, and latent heat of water vaporization at varying degrees consume microwave dissipation in BLRC. The results provide guidance for understanding microwave heating uniformity and processing technology for agricultural products with similar properties as berry fruit.