Thin layer drying model of local rice grain Siam mutiara variety from tidal swamp land in South Kalimantan

Abstract

As staple food in many countries, rice is one of the most important cultivated plant. Indonesia is the third largest rice producer in the world with annual production of 54,65 million tons. South Kalimantan province has 191,740 ha of tidal swamp land, which equivalent to 30% of its total area. Paddy rice variety planted in this region is dominated by local varieties, such as Siam Mutiara. Local farmers prefer this variety due to its high demand and high selling price than other local rice varieties. This variety produces soft textured rice which is preferred by the people of South Kalimantan. In addition to the taste and texture, physical aspects such as wholeness of the grain is also important for consumers, and this aspect is affected by post-harvest processed such as drying. In this study, drying characteristics of Siam Mutiara variety was studied. Samples of Siam Mutiara from Jelapat 1 village, Barito Kuala district were dried using a Fixed Bed Dryer at three temperatures (40, 50, and 60°C) and an airflow rate of 1 m/s. The samples were dried in five trays made of PVC pipes (5” diameter and 1” length) which arranged vertically. The first four trays were used to dry paddy rice sample with a layer of 1 cm thick, and the lowest tray were used to dry the sample in a single layer grain (with average thickness of grain width 1,66 mm). The temperature and humidity at each tray monitored continuously, and the weight of the sample in each tray was measured every 30 minutes. The results of this study indicate that the temperature and humidity varied among the trays, where the lowest tray had the highest temperature and the lowest air humidity. However, moisture content of the samples in all of the trays are relatively similar for both the top four trays (with total of 4 cm) and the lowest tray (single layer). This result indicates that for Siam Mutiara variety, a total of 4 cm thick layer can still be considered as a thin layer drying. It also found that the effect of drying temperature on drying rate is significant. In addition, the drying characteristic of this rice variety can be best modelled using Page Model.