Influence of soaking pressure and temperature on the moisture content of rice and establishment of model parameters
| Autor: | LI, JIA-YAN, 李佳燕 |
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| Rok vydání: | 2019 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 107 Rice (Oryza sativa L.) is one of the most important cereals in the world and is parboiled to bring about desirable properties for consumption as staple food. Parboiling is a hydrothermal treatment including soaking, steaming and drying. Soaking is a hydration process in which diffusion controlled water uptake migrates into the rice kernel and subsequent heating leads to irreversible swelling and fusion of starch granules. The relationship between the moisture content and the hydration time of the grain in the soaking process can be analyzed by a mathematical model, and is called hydration kinetics. This study will explore influence of soaking pressure and temperature on the moisture content of KH145. Through the introduction of the relevant models of the literature, a more suitable mathematical formula and related parameters were found, and a parboiled rice process engineering model was provided and established. In general, the moisture content gradually increases to the equilibrium moisture content with the soaking time. The increase of temperature resulted in the increase of water absorption capacity, and the kinetic curves at different temperatures showed similar trends. Under the same soaking conditions, the rate of water absorption showed paddy < brown rice < white rice. This was known that rice husk and bran can affect water diffusion. There were significant differences (Δ) between vacuum soaking and atmospheric soaking for paddy;Δ0→1was raised from 0.033 - 0.084 to 0.165 - 0.221. The air between husk and bran was removed in vacuum soaking, which accelerates the moisture diffusion. The statistical parameters R2 of empirical models suggested by Page and Peleg were both larger than 0.808, which also performed better fitting situations than the theoretical models. Due to the Fick model could not correctly predict the initial moisture content, it was impossible to accurately fit the hydration process during a short period (< 1 hr); while the Omoto model and the Nicolin model could correctly predict the initial moisture content. The Nicolin model performed the best fit situation among the theoretical models, because the model composed more undetermined parameters to be characterized by the experimental data. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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