In this study, the effects of ethanolic KOH concentration, reaction temperature, and reaction time to free fatty acid (FFA) percentage were investigated. D-optimal design was employed to study significance of these factors and optimum condition for the technique predicted and evaluated. The optimum conditions for maximum FFA% were achieved when 1.75？M ethanolic KOH concentration was used as the catalyst, reaction temperature of and reaction time of 2.0？h. This study showed that ethanolic KOH concentration was significant variable for saponification of J. curcas seed oil. In an 18-point experimental design, percentage of FFA for saponification of J. curcas seed oil can be raised from 1.89% to 102.2%. 1. Introduction Saponification of oils is the applied term to the operation in which ethanolic KOH reacts with oil to form glycerol and fatty acids. Production of fatty acid and glycerol from oils is important especially in oleochemical industries. Glycerol and fatty acids are widely used as raw materials in food, cosmetics, pharmaceutical industries [1, 2], soap production, synthetic detergents, greases, cosmetics, and several other products [3]. The soap production starting from triglycerides and alkalis is accomplished for more than 2000 years by [4]. These reactions produce the fatty acids that are the starting point for most oleochemicals production. As the primary feedstocks are oils and fats, glycerol is produced as a valuable byproduct. Reaction routes and conditions with efficient glycerol recovery are required to maximize the economics of large-scale production [5]. Lipid saponification is usually carried out in the laboratory by refluxing oils and fats with different catalysts [6]. The reaction can be catalyzed by acid, base, or lipase, but it also occurs as an uncatalyzed reaction between fats and water dissolved in the fat phase at suitable temperatures and pressures [7]. Researchers have used several methods to saponify oils such as enzymatic saponification using lipases from Aspergillus niger, Rhizopus javanicus, and Penicillium solitum [8], C. rugosa [1], and subcritical water [3]. Historically, soaps were produced by alkaline saponification of oils and fats, and this process is still referred to as saponification. Soaps are now produced by neutralization of fatty acids produced by fat splitting, but alkaline saponification may still be preferred for heat-sensitive fatty acids [9]. Nowadays, researchers have used potassium hydroxide-catalyzed hydrolysis of esters which is sometimes known as saponification because of its relationship with soap
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