World Journal of Agricultural Sciences 4 (4): 409-415, 2008 ISSN 1817-3047 © IDOSI Publications, 2008 Corresponding Author: S. Siriamornpun, Department of Food Technology and Nutrition, Faculty of Technology, Mahasarakham University, Mahasarakham, 44000, Thailand 409 Effect of Soaking Temperature on Physical, Chemical and Cooking Properties of Parboiled Fragrant Rice K. Sareepuang, S. Siriamornpun, L. Wiset and N. Meeso 1 1,2 2 2 Department of Food Technology and Nutrition, Faculty of Technology, 1 Mahasarakham University, Mahasarakham, 44000, Thailand Research Unit of Drying Technology for Agricultural Products, 2 Faculty of Engineering Mahasarakham University, Khantharawichai, Mahasarakham 44150, Thailand Abstract: KDML 105 is the most popular fragrant rice for export and consumption in Thailand but it has poor milling yield. To solve this problem, parboiling has been used for improving milling quality of damaged rice. Our present study investigated the effect of soaking temperature on physical, chemical and cooking properties of parboiled rice. The 12-month stored KDML 105 paddy samples were soaked at 40, 50 and 60°C for 3 h, then autoclaved with steam at 121°C 15 min and dried by cabinet tray dryer at 60°C to reach the moisture content of 23 g/100 g dry matter. Head milling yield was significantly increased from 51% in brown rice to 60-80% in parboiled rice. The results also showed that parboiling process significantly (p<0.05) increased protein, lipid and ash contents. Overall, soaking at 50°C for 3 h prior to steaming and drying was found to provide the most desirable quality of parboiled rice in our study in terms of nutritional quality and sensory properties. Key words: Soaking temperature Parboiled rice Physical properties Chemical properties Cooking quality INTRODUCTION Several studies have reported on parboiling Khao Dawk Mali 105 (KDML 105) is the most popular Traditionally, parboiling consists of steeping rough rice aromatic rice variety in Thailand, in terms of production, in water at room temperature followed by steaming or consumption and export. Because of its famous reputation boiling at 100°C and sun-drying. Recently, more in appearance, cooking quality and high aroma level, the sophisticated procedures such as dry-heat parboiling and rice has gained an increasing popularity throughout the pressure parboiling have been applied [5]. Soaking at world food market. However it is sensitive to heat and room temperature (traditional method of parboiling) is fragile during handling, causing poor milling yield. slow and that causes microbial contamination while hot Therefore, improvement of milling quality of damaged soaking (CFTRI method) requires precise control and grain is needed. special care because a steep temperature and moisture Parboiling is a process developed for improving rice gradient develops and may cause sloughing-off of the quality. It consists of soaking, steaming and drying of the surfaces before hydration up to the core of the kernel is rough rice. The major reasons for parboiling rice include achieved. It has been suggested that starting soaking of higher milling yields, higher nutritional value and paddy at 75°C and allowing the batch to cool naturally resistance to spoilage by insects and mold [1, 2]. The ensures the fastest possible hydration without parboiling process is applied to rice with a preliminary complication [2]. However, such hot soaking requires objective of hardening the kernel in order to maximize precise control [6]. head rice yield in milling. Besides milling yield, it was also Therefore this study aimed to investigate the effect of the realization of the nutritional and health benefits of soaking temperature on cooking quality physicals, parboiled brown rice [3] compared to raw brown rice that chemicals and cooking properties of parboiled rice. We created the awareness and importance of parboiling were especially interested in parboiling of fragrant rice among consumers and manufacturers. which was quite fragile and kept for a long period of time. processes as reviewed by Luh and Mickus [4].