For open sun drying experiments samples were simply laid on a mesh under direct sun light. For each run, 250 g of samples were weighted with an electronic balance (AND EK-3000i, Japan). In order to avoid environmental influences, it was put in a cage placed parallel to solar collector. Weight change and outside temperature were recorded for every half hour. Dried samples were stored in closed plastic bags to avoid change in moisture content for further analysis. Drying experiments were repeated 3 times.