Abstract—A herb, Orthosiphon stamineus is a popular traditional medicine for centuries to treat many human illness especially diseases of urinary tract and kidney stones. Moisture adsorption study of O. stamineus leaves is important because this herb is stored and consumed in its dried form. The behavior of dried leaves under different conditions during storage can have an impact on the final quality of end product. In this research, moisture adsorption isotherms were developed at 2 different temperatures of 5 ^oC and at ambient (30 ^oC) and at 6 levels of relative humidity (RH) ranging from 11.3 % to 98.5 % by using the static gravimetric method. Microbial growth on the samples were also observed. The moisture adsorption of O. stamineus was found to be of type III isotherm (J-shaped). The equilibrium moisture content (EMC) is higher at low temperature compared to the higher temperature at all RH levels. For example, at RH level of 98.5 % the EMC is 0.58 g water/g dry matter (dry basis- d.b) and 0.48 g water/g dry matter (d.b) at 5 ^oC and 30 ^oC respectively. Microbial growth was observed to present for samples at RH more than 75 % as early as day 6th of experiment at ambient temperature (30 ^oC) whereas for samples at 5 ^oC microbial growth was observed to present at RH of 98.5 % after 54 days of experiment.

Index Terms—Equilibrium moisture content, isotherm, microbial growth, moisture adsorption.

Sriyana Abdullah, Abd Razak Shaari, Muhammad Syarhabil Ahmad, Rashidah Ruslan, and Ibni Hajar Rukunudin are with the School of Bioprocess Engineering, University Malaysia Perlis, 02600 Arau Perlis Malaysia (e-mail: sriyana@unimap.edu.my, ibnihajar@unimap.edu.my, razakshaari@unimap.edu.my, syarhabil@unimap.edu.my, rashidahruslan@unimap.edu.my).

 

Cite:Sriyana Abdullah, Ibni Hajar Rukunudin, Abd Razak Shaari, Muhammad Syarhabil Ahmad, and Rashidah Ruslan, "Moisture Adsorption Isotherms of Orthosiphon Stamineus Leaves," International Journal of Bioscience, Biochemistry and Bioinformatics vol. 3, no. 4, pp. 357-359, 2013.