MRI temperature mapping and determination of liquid-particulate heat transfer coefficient in an ohmically heated food system

Real-time temperature maps of ohmically heated liquid-particulate mixtures were acquired using the Proton Resonance Frequency (PRF) shift method incorporated into a fast Magnetic Resonance Imaging (MRI). Noise in the MRI images induced by the electrical heating power was eliminated by a post-processing algorithm of the PRF shift method and correction phase images. The time-dependent interface heat transfer coefficients (h_fp) were determined during the holding period using the MRI temperature maps and numerical solutions to the Fourier's 2nd law. The calculated values of h_fp range from 30 to 105 W/m^2.K, consistent with literature values for natural convection. These results provide crucial data for understanding the ohmic heating process.