Experimental study on the drying process characteristics of alfalfa

Both alfalfa drying property and constant K involving drying parameters of the alfalfa were studied. Due to the difference in physical structure and chemical characteristics of fresh alfalfa component, the leaf, fine stem and coarse stem show different drying rates under the same drying condition.The higher the heated air temperature is, the higher the drying speeds of the drying speeds of the stems and leaf are. As drying temperature is over 120℃, the drying rate was found to increase significantly with initial alfalfa moisture content. This may be attributed to thermal damage to waxy surface, which helps moisture retention in the plant, thereby increasing drying rate up to a critical level. The changes of the stem, the leaf and the whole stalk drying rates with the heated air temperature were obtained. In order to reduce the moisture difference between the stems and leaf of the post-drying alfalfa, it is necessary to crush the stems through mechanical treatment. The dimensional analysis method was used to establish an empirical equation involving the drying kinetic constant K and the initial moisture content, heated air velocity and temperature etc. The equation is useful to feasibly determine the drying parameters, which may better preserve the shape, color and flavor of the post-drying alfalfa, and reduce its nutritional component loss such as protein, vitamin etc.