| Summary: | 博士 === 輔仁大學 === 食品營養博士學位學程 === 107 === Wheat germ (WG) is a precious by-product from wheat milling process, natural and source. The main factor to determine the storage quality of WG is water activity, which is directly related to the moisture content (MC) of WG. Appropriate drying can reduce the lipid hydrolysis and enzymatic oxidation and consequently lower the rancidity and extend the shelf life of WG. Meantime, drying is one of the effective methods for material stabilization. Fluidized bed drying (FBD) is one of the technologies to attain this goal. Its efficiency depends on the size of fluidized bed, operation conditions (heating temperature and time: time-temperature history), material loading and air humidity and temperature. The objective of this research were to develop the engineering model for analysis the dehydration and condensation during WG drying in the FBD in order to reduce the trial and error, and to evaluate the energy efficiency of different time-temperature combination and loading during WG drying. The optimization of WG drying was based on the experimental data and simulation results. The drying process of WG was divided into four stages: preheating, loading, heating and cooling stage in fluidized bed system. The methods used in this thesis were divided into two parts: experimental measurement and numerical simulation. The air temperature, water activity and moisture content of WG during drying were measured. A mathematical model coupling with the macro-heat transfer model and the bubble model were developed to simulate the dehydration and condensation phenomena during WG drying in the FBD. From the results of the experimental and theoretical studies, a mathematical model coupling with the macro-heat transfer model and the bubble model was developed to simulate the dehydration and condensation phenomena during WG drying in FBD. The thermal input of the drying process with short heating time approach was one-third of that of the drying process with traditional heating approach. All time-temperature combinations could dry the WG to the target temperature of 45 °C and water activity of 0.3 ±0.1. The WG dehydration and condensation could also be evaluated by the dehydration flux and the condensation flux, respectively. A linear relation was obtained between WG loading and heating time. An optimization condition of WG drying process had been successfully applied for an industrial-scale FBD. Meantime, with the optimization condition and the industrial-scale FBD operation lead to the development of a new design of FBD.
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