Alaei Behnam, Chayjan Reza Amiri
Department of Biosystems Engineering, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran.
Acta Sci Pol Technol Aliment. 2015 Jan-Mar;14(1):15-27. doi: 10.17306/J.AFS.2015.1.2.
Drying of nectarine slices was performed to determine the thermal and physical properties in order to reduce product deterioration due to chemical reactions, facilitate storage and lower transportation costs. Because nectarine slices are sensitive to heat with long drying period, the selection of a suitable drying approach is a challenging task. Infrared-vacuum drying can be used as an appropriate method for susceptible materials with high moisture content such as nectarine slices.
Modelling of nectarine slices drying was carried out in a thin layer near infraredvacuum conditions. Drying of the samples was implemented at the absolute pressures of 20, 40 and 60 kPa and drying temperatures of 50, 60 and 70°C. Drying behaviour of nectarine slices, as well as the effect of drying conditions on moisture loss trend, drying rate, effective diffusion coefficient, activation energy, shrinkage, colour and energy consumption of nectarine slices, dried in near infrared-vacuum dryer are discussed in this study. Six mathematical models were used to predict the moisture ratio of the samples in thin layer drying.
The Midilli model had supremacy in prediction of nectarine slices drying behaviour. The maximum drying rates of the samples were between 0.014-0.047 gwater/gdry material·min. Effective moisture diffusivity of the samples was estimated in the ranges of 2.46·10-10 to 6.48·10-10 m2/s. Activation energy were computed between 31.28 and 35.23 kJ/mol. Minimum shrinkage (48.4%) and total colour difference (15.1) were achieved at temperature of 50°C and absolute pressure of 20 kPa. Energy consumption of the tests was estimated in the ranges of 0.129 to 0.247 kWh.
Effective moisture diffusivity was increased with decrease of vacuum pressure and increase of drying temperature but effect of drying temperature on effective moisture diffusivity of nectarine slices was more than vacuum pressure. Activation energy was decreased with decrease in absolute pressure. Total colour difference and shrinkage of nectarine slices on near infrared-vacuum drying was decreased with decrease of vacuum pressure and decrease of drying temperature.
进行油桃切片干燥以确定其热物性和物理性质，从而减少因化学反应导致的产品变质，便于储存并降低运输成本。由于油桃切片对热敏感且干燥周期长，选择合适的干燥方法是一项具有挑战性的任务。红外真空干燥可作为处理油桃切片等高水分敏感材料的合适方法。
在近红外真空条件下对油桃切片干燥进行薄层建模。样品在20、40和60 kPa的绝对压力以及50、60和70°C的干燥温度下进行干燥。本研究讨论了在近红外真空干燥机中干燥的油桃切片的干燥行为，以及干燥条件对油桃切片水分损失趋势、干燥速率、有效扩散系数、活化能、收缩率、颜色和能耗的影响。使用六个数学模型预测样品在薄层干燥中的水分比。
Midilli模型在预测油桃切片干燥行为方面具有优势。样品的最大干燥速率在0.014 - 0.047 g水/g干物质·分钟之间。样品的有效水分扩散率估计在2.46×10⁻¹⁰至6.48×10⁻¹⁰ m²/s范围内。计算得到的活化能在31.28至35.23 kJ/mol之间。在50°C的温度和20 kPa的绝对压力下实现了最小收缩率（48.4%）和总色差（15.1）。试验的能耗估计在0.129至0.247 kWh范围内。
有效水分扩散率随真空压力降低和干燥温度升高而增加，但干燥温度对油桃切片有效水分扩散率的影响大于真空压力。活化能随绝对压力降低而降低。近红外真空干燥时油桃切片的总色差和收缩率随真空压力降低和干燥温度降低而减小。
