화학공학소재연구정보센터
Journal of Food Engineering, Vol.104, No.4, 525-531, 2011
Moisture profiles in cheese drying determined by TD-NMR: Mathematical modeling of mass transfer
A time-domain nuclear magnetic resonance (TD-NMR) method is proposed to quick and easily determine moisture profiles during cheese drying. The method consists of a combined relaxation analysis, where the magnetization at a certain time is determined by both the longitudinal and the transverse NMR relaxation processes. The drying experiments were carried out at 16 degrees C and 0.2-0.5 m/s for 32 days, and allowing only one-direction mass transfer. A diffusion model was formulated taking into account the external resistance to mass transfer. Both effective moisture diffusivity and external mass transfer coefficient were simultaneously identified (3.71 x 10(-11) m(2)/s and 2.95 x 10(-8) m/s, respectively). The proposed model allowed a satisfactory simulation of both the drying curve (mean relative error (MRE) = 0.4% and percentage of explained variance (%var) = 99.7%) and the moisture profiles (average MRE = 4.4% and %var = 94.5%). (C) 2011 Elsevier Ltd. All rights reserved.