Saskatoon berry (Amelanchier alnifolia) is a high moisture content fruit crop, harvested at 75–80% moisture content (w. b.) and dried to lower moisture contents for a safe, extended shelf-life and for further usage in food applications. Saskatoon berries were driedfrom an initial moisture content of 75.5% to around25% (w.b.) using microwave-vacuum drying. In this study, saskatoon berries were dried at different microwave power levels P10 (745 W), P7 (514 W) andP5 (374 W) and vacuum pressure levels V20 (67.0 kPa) and V10 (33.5 kPa). The vacuum pressure levels did not greatly influence the drying time of the saskatoon berries compared to the microwave power levels. Increasing the microwave power level produced faster drying times for the samples. After 12 min of drying at power level P10, the moisture contents of the samples at vacuum pressures of 33.5 and 67.0 kPa were 29.74 and 31.24%, respectively. However, after dryingfor 12 min at vacuum pressure of 33.5 kPa, the moisture contents atpower levels P10, P7 andP5 were 29.74, 51.41 and 61.95%, respectively. Polynomial and exponential models were fitted to the drying data. The exponential model provided a better fit for the drying data at the lower vacuum pressure, with higher R2 and lower SE compared to the polynomial model. On the other hand, the polynomial model provided a better fit for the drying data at the higher vacuum pressure. The vacuum pressure and the microwave power levels did not significantly change the yellowness of the samples at indicated by the Ab values. However, microwave-vacuum drying produced significant color changes in the L (white = 100 to black = 0) and a (green = -a to red = +a) values as indicated by AL and Aa. Total color difference was dependent on microwave power and vacuum pressure levels. Water activity of the samples after drying ranged from 0.61 to 0.75 for moisture content range of 15.68 to 29.03%.

中文翻译：

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微波真空干燥萨斯卡通浆果的干燥动力学及品质特性

萨斯卡通浆果 (Amelanchier alnifolia) 是一种高水分含量的水果作物，以 75-80% 的水分含量 (wb) 收获并干燥以降低水分含量，以确保安全、延长保质期并进一步用于食品应用。使用微波真空干燥将萨斯卡通浆果从 75.5% 的初始水分含量干燥至约 25% (wb)。在这项研究中，萨斯卡通浆果在不同的微波功率水平 P10 (745 W)、P7 (514 W) 和 P5 (374 W) 以及真空压力水平 V20 (67.0 kPa) 和 V10 (33.5 kPa) 下干燥。与微波功率水平相比，真空压力水平对萨斯卡通浆果的干燥时间没有太大影响。增加微波功率水平会使样品的干燥时间更快。在功率水平 P10 下干燥 12 分钟后，在真空压力为 33.5 kPa 和 67.0 kPa 时，样品的水分含量分别为 29.74% 和 31.24%。然而，在33.5 kPa的真空压力下干燥12分钟后，功率水平P10、P7和P5的水分含量分别为29.74、51.41和61.95%。多项式和指数模型拟合干燥数据。与多项式模型相比，指数模型更好地拟合了较低真空压力下的干燥数据，具有更高的 R2 和更低的 SE。另一方面，多项式模型在较高真空压力下为干燥数据提供了更好的拟合。真空压力和微波功率水平没有显着改变样品在 Ab 值所指示的黄度。然而，微波真空干燥在 L（白色 = 100 到黑色 = 0）和 a（绿色 = -a 到红色 = +a）值中产生显着的颜色变化，如 AL 和 Aa 所示。总色差取决于微波功率和真空压力水平。干燥后样品的水分活度为 0.61 至 0.75，水分含量范围为 15.68 至 29.03%。