秈米糕類蒸製過程的熱傳研究

「蒸」是亞洲常見的烹飪方法之一，在西方並不常見，而在食品工業上，常利用蒸汽凝結成的水滴或水膜並釋出蒸發潛熱，食物表面接觸到高溫的蒸汽並凝結的情況下，其表面對流熱傳係數高達數千W/m^2K，讓表面溫度快速提昇並迅速傳熱至各部位，然而回顧文獻，蒸煮的熱質傳研究仍相當少。本研究之目的針對日常生活中常用於蒸煮的電鍋，經實驗並使用整體模式法推估其表面對流熱傳係數，接著代入米糕類蒸製過程中的熱質傳模型並與實驗比較。實驗裡以DSC熱量分析儀去量測米糕與米漿的比熱與糊化熱，並利用線熱源法自製熱傳導係數探針去量測熱傳導係數，再由有限元素軟體COMSOL Multiphysics模擬驗證米糕蒸煮升溫過程。由預備蒸煮實驗結果可知水分傳遞對於蘿蔔糕的熱傳影響很小，故此研究之統御方程式使用單純熱傳導方程式並考慮糊化熱的影響。此外整體模式法求得的表面對流熱傳係數僅只有文獻上純蒸汽的一半，顯示蒸汽品質對於對流熱傳係數的影響很大。而模擬米糕與米漿蒸煮方面，蒸煮秈米糕實驗與模擬升溫數據之間的誤差為5.8%，而模擬蒸煮秈米漿時考慮糊化溫度範圍內秈米漿比熱的上升作為模擬糊化焓值，其誤差僅為7.4%，因此本研究的模擬數據相對於實驗能有正確的再現性，而其模擬之變化參數可做為現有蒸煮過程作品質控管的改善依據。

關鍵字

蒸煮；對流熱傳係數；澱粉糊化

並列摘要

Steaming is commonly used as a heating medium in preparing Chinese cuisine, but studies on heat transfer in steaming of food is very scarcely to be found in literatures. In this study, mathematical models for predicting the temperature history of radish cakes and rice flours dough during steaming in a rice cooker were developed, and simulated in finite element software (COMSOL Multiphysics) using the surface heat transfer coefficient evaluated by lumped- mass method. Thermal conductivity was measured by heat line source method and specific heat was obtained from differential scanning calorimetry (DSC). Based on the experimental results for the steam reheating of radish cakes, the pure conductive model with reaction heat was presumed to be the governing model. Besides, the estimated surface heat transfer coefficient was only half of that from the literatures which indicated that quality of steam has significant effects on the coefficient. In the simulation of rice flours solution, varied specific heat referred to DSC result was modified in COMSOL Multiphysics calculation. The model was successfully constructed with an average errors 7.4 % between the experiment and simulation by considering the gelatinization enthalpy. Also, the average errors between simulation and experiment for non gluten rice cake steaming were about 5.8%. The implications of these models may be useful for understanding heat and mass transfer model of steaming of food and then set up a good quality assessment.

並列關鍵字

Steaming process ； Convection heat transfer coefficient ； Gelatinization

國際替代計量

秈米糕類蒸製過程的熱傳研究

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