International Journal of Scientific Engineering and Technology (ISSN : 2277-1581) Volume No.4 Issue No.2, pp : 40-44 01 Feb. 2015 IJSET@2015 Page 40 Mathematical Modeling of Equilibrium Moisture Content of Local Cardamom (Amomum cardamomum Wild) Sigit Triwahyudi 1 , Budi Rahardjo 2 , Leopold O. Nelwan 3 and Dyah Wulandani 3 1 Indonesian Center for Agricultural Engineering Research and Development, Tromol Pos 2, Serpong, Tangerang, Banten 15310 Indonesia 2 Department of Agricultural Engineering, Faculty of Agricultural Technology, Gadjah Mada University, Jl. Sosio Justisia, Bulaksumur, Yogyakarta - 55281, Indonesia 3 Department of Agricultural Engineering, Bogor Agricultural University, PO Box 220 Bogor16002, Indonesia E-mail : sigittriwahyudi@yahoo.com Abstract: The objective of this work was done to investigate the effect of temperature and relative humidity on the equilibrium moisture content (EMC) of local cardamom (Amomum cardamomum Wild) and to get the appropriate mathematical models. The EMC of local cardamom were determined by dynamic method using laboratory air dryer at the temperature of 40, 50 and 60 0 C and at the relative humidity of 20, 40 and 60%. Four widely used three parameters sorption isotherms equations such as modified Henderson, modified Chung–Pfost, modified Oswin and modified Halsey were used to fit the experimental data. The accuracy of the model was evaluated by comparing the value of the coefficient of determination (R 2 ) and the value of the root mean square error (RMSE) between the experimental and the predicted value of EMC by using nonlinear regression analysis. The effects of relative humidity were found to significantly influence the EMC. Based on statistical analysis the modified Chung-Pfost equation have the highest value of R 2 = 0.979 and the lowest value of RMSE = 0.758, it can be seen that the modified Chung-Pfost equation has the ability to properly describe EMC of local cardamom on a selected range of temperature and relative humidity. Keywords: Equilibrium moisture content; dynamic methode; mathematical modelling; local cardamom I. Introduction Local cardamom (Amomum cardamomum Wild or Amomum compactum soland ex Maton) is native to Indonesia and endemic plants in hilly area in western Java. Now grown and may be wilder in various places, Local cardamom mainly produced commercially from West Java and southern Sumatra. Cardamom is a fruit that is often used as spices (seasonings) for certain dishes and also for a mixture of herbs. Local cardamom was reported contains 2 – 5% of essential oil comprising mainly 1,8% cineol (up to 70%) and -pinene (16%) (Lim, 2013), -pinene, -terpineol and humulene were also found. During heating these components will evaporate along with the water vapour at a temperature below the boiling point. According to Ketaren (1985) the recommended temperature for drying spices was maximum of 60 0 C, while drying temperature for cardamom was not above 50 0 C (Ali, 2007). The fresh local cardamom capsules contain about 70 – 80% moisture (on wet basis) depending upon the maturity level of the capsules at time of plucking (Rao et al., 2001). Because of high water content, local cardamom should be quickly processed to reduce the risk of damage. Dehydration of foods is one of the most common processes used to improve food stability, since it decreases considerably the microbiological activity and minimizes physical and chemical changes during it storage (Babetto et al., 2011). Also, it extends the shelf-life with sensorial characteristics similar to those of fresh products (Sacilik & Unai, 2005). The concept of equilibrium moisture content is an important factor in the process of drying of agricultural products. Equilibrium moisture content can be used to determine the drying time for these commodities, structures and components for the dryer, and the cost required for the drying process (Akanbi et al,. 2006; Chowdhury et al., 2006) According to Bala (1997), there are two ways or methods to determine the equilibrium moisture content is a static method and dynamic method. In the static method the sample is allowed to come to equilibrium in still moist air, usually a chemical solution used to maintain a stable RH environmental. In order to achieve equilibrium may take several days. In the dynamic method requires a mechanism movement of air flow, this way is faster, but has disadvantage in its RH control. Dynamic methods commonly used in the analysis of drying process while the static method for the analysis of storage. Many researchers have developed a mathematical equation, theoretical, semi-theoretical and empirical sorption isotherm to describe the groceries. Four commonly used equation is modified Henderson, modified Chung-Pfost, modified Halsey and modified Oswin (Chowdhury et al., 2006; Aviara et al., 2006; Arabhosseini et al., 2010; Raji and Ojediran, 2011, Argyropoulos et al., 2012; Chenarbon et al., 2012) as shown in Table 1. The equation has been adopted as standard equations by the American Society of Agricultural Engineers (ASAE) to describe the sorption isotherms (ASAE, 1999). According to the Sun and Woods (1997), modified Chung- Pfost equation and modified Oswin equation is most suitable for grain products. Meanwhile, according to Sitompul et al.