Food Sci. Biotechnol. 20(6): 1525-1531 (2011) DOI 10.1007/s10068-011-0211-6 Optimization of Isoflavone Production from Fermented Soybean Using Response Surface Methodology Harisun Yaakob, Roslinda Abd Malek, Mailin Misson, Muhammad Fauzi Abdul Jalil, Mohd Roji Sarmidi, and Ramlan Aziz Received: 21 April 2011 / Revised: 6 September 2011 / Accepted: 6 September 2011 / Published Online: 31 December 2011 © KoSFoST and Springer 2011 Abstract This study was conducted to investigate the interaction effects among process variables during isoflavone production and optimized the yield of isoflavone. A response surface methodology (RSM) was employed to study the relationships of fermentation temperature, time, and starter culture on daidzin and daidzein as an isoflavone product. The experiments were designed using central composite by applying 2 4 factorial designs with 2 center points. Fermented soybean produced a maximum of 1,284.14 μg/g daidzin at an optimum temperature of 29.39 o C, fermentation duration at 32.06 h and starter culture content of 0.96%(w/w). Meanwhile, an optimum daidzein (1,663.85 μg/g) was obtained at 35 o C and 48 h fermentation process with 0.5%(w/w) starter culture. Validation study showed the observed and predicted values were in compliance with 5% level of significance. The RSM was successful in identifying the optimum conditions for the isoflavone production. Keywords: isoflavone, response surface methodology (RSM), daidzin, daidzein Introduction Soybean has been used for a long time and has becoming an increasingly important source of nutrients and phytochemicals (1). The essential phytochemicals include isoflavones, tocopherols, saponins, anthocyanins, and phenolic acids (2,3). Isoflavone from soybean is classified as phytoestrogen due to its estrogenic activity in mammals. Estrogenic activity of isoflavone is similar to stilbestrol, which is commonly used in hormone replacement therapy (4). A diet rich with isoflavones is associated with the variety health-related benefits. Isoflavones have been investigated in a number of clinical and in animal studies to determine their health protective effects. Isoflavones was reported to reduce the risk of cardiovascular disease due to the metabolism of lipids such as cholesterol (5). In addition, isoflavone improves bone health by alleviating symptoms of osteoporosis occurring after menopause (6). To date, 12 chemical forms of isoflavone have been found in soybeans, including 3 aglycones (i.e. daidzein, genistein, and glycitein) and their glycosides, acetyl-, malonyl-, and β-glycosides (7). For example, daidzein which is present as an aglycone, can be further metabolized to equol, a compound with greater estrogenic activity and more bioavailable than other isoflavones (8,9). Soybeans and soy foods are the major components of dietary sources of these substances. Daidzein glycosides are the second most abundant isoflavones in soybeans and soy foods. Nonfermented soy foods, such as tofu, contain daidzein, principally in its glycoside form is daidzin. Tempe and miso are the examples of fermented soy foods, which contain significant levels of the aglycone. With regards to the awareness on the role of isoflavone from fermented food in health maintenance, the processing techniques of soy products that retain their biological activity of the product are important. The research in the extraction of phytoestrogen from fermented soybean is expected to contribute valuable experimental data for the phytochemical research and the appropriate processing technology for functional soybean foods. Processing is known to affect the characteristics of the products such as Harisun Yaakob ( ), Roslinda Abd Malek, Mailin Misson, Muhammad Fauzi Abdul Jalil, Mohd Roji Sarmidi, Ramlan Aziz Institute of Bioproduct Development, University Teknologi Malaysia, Skudai, Johor, Malaysia Tel: +6075532502; Fax: +6075569706 E-mail: harisun@ibd.utm.my RESEARCH ARTICLE