Advance Journal of Food Science and Technology 4(4): 199-206, 2012 ISSN: 2042-4876 © Maxwell Scientific Organization, 2012 Submitted: May 30, 2012 Accepted: July 02, 2012 Published: August 20, 2012 Corresponding Author: Tajul A. Yang, Food Technology Division, School of Industrial Technology, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia, Tel.: +6019 456 3688 199 The Physical Properties of N. lappaceum Seed as a Function of Moisture Content Nor Syafarah Zakariya and Tajul A. Yang Food Technology Division, School of Industrial Technology, Universiti Sains Malaysia, 11800 Pulau Pinang, Malaysia Abstract: This study studies the effect of 4 level of moisture content; 12.2333, 11.7133, 10.8167 and 10.3133% on physical properties (geometrical, gravimetrical and frictional properties). The results show that width, height and length were in negative linear relationship with moisture content as shown by the regression equation. Whereas sphericity, true density and static coefficient for all surfaces investigated exhibited negative quadratic model relationship, except for sphericity which positively correlate with moisture content. Cubic relationship were signified by arithmetic mean diameter, geometric mean diameter, surface area, mass, bulk density, porosity, filling and emptying angle of repose. Thus, by investigating the effect of moisture content on these physical properties, one can determine the most suitable condition for processing, transporting and storing of N. lappaceum seed. Keywords: Frictional properties, geometrical, gravimetrical, N. lappaceum, physical, rambutan INTRODUCTION The centre of origin of Nephelium lappaceum or generally known as rambutan was possibly the Malay Archipelago and belongs in the same family (Sapindacae) as the subtropical fruits; lychee and longan (Ong et al., 1998). This seasonal fruit grows in Asia countries such as Malaysia, Thailand, Indonesia and others. In Malaysia, it covered 26, 946 hectare and able to produce 86, 085 metric tons of fruits in 2011 at Kelantan, Johor, Terengganu, Pahang and Kedah (Norlia et al., 2011). There are a total of 62 clones of rambutan were registered by 1986. Only 7 of these clones were recommended for general planting due to many of the original clones yield only under specific environmental conditions. These includes R3 (‘Peng Thing Cheng’), R134, R156 (‘Muar Gading’), R160 (‘Khaw Tow Bak’), R161 (‘Lee Long’), R162 (‘Daun Hijau’) and R170 (‘Deli Cheng’) (Tindall, 1994). Generally, N. lappaceum is consumed fresh and in certain places, it is processed in the industry as juices, jams, jellies and marmalades. In some Asian countries, the residues left from these processes; N. lappaceum seeds were considered as an edible food after went through certain process (Solís-Fuentes et al., 2010). Prior to utilizing N. lappaceum seed as food, it is important for it to be dried before further processed. The drying operation affects the quality and nutritious level by stabilizing the storage condition, undesirable chemical reaction, longer shelf life and retards or eliminates the growth of microorganism thus preventing rot (Nejad et al., 2003; Kashaninejad and Tabil, 2009; Abano and Amoah, 2011). After drying to certain level of moisture content, the seeds will be stored or packaged for allocation. There are 3 types of physical properties of N. lappaceum seed as a function of moisture content to be analyzed. Those are geometrical properties, gravimetrical properties and frictional properties. Geometrical properties include length, wide, height, sphericity and surface area (Razavi et al., 2007a). It is essential to obtain the information on the geometrical properties of the seeds at different moisture level for the accurate equipment design for structural, processing, cleaning, grading, separation and storing as well practical utility in control engineering (Amin et al., 2004; Milani et al., 2007; Gharibzahedi et al., 2010). To design such equipment that responsible in aeration, drying, storage and transport, gravimetrical properties is important to be considered. True density, bulk density and porosity have their own specific role; designing separating equipment (separation of desirable materials and impurities), capacity of storage and transport systems and determination of the resistance of air flow during aeration and drying of seeds are their roles respectively (Altuntas and Yıldız, 2007; Tavakoli et al., 2009; Gharibzahedi et al., 2010) The volume and density are significant as they play a major role in numerous technological processes as well as in the evaluation of product quality (Ozguven and Vursavus, 2005). From the data acquired for porosity, one can design the force ventilation system for drying and cooling the stored bulk as the resistance to airflow through the seed is an important parameter