Equilibrium Journal of Chemical Engineering 7(1) (2023) 069–077 EQUILIBRIUM JOURNAL OF CHEMICAL ENGINEERING Homepage:https://jurnal.uns.ac.id/equilibrium Equilibrium Journal of Chemical Engineering, e-ISSN 2622-3430 69 Response Surface Methodology-Based Parameter Optimization of Candlenut Seeds (Aleurites moluccana Willd) Extraction Yeni Variyana a* , Dewi Ermaya a , Shintawati Shintawati a , Devy Cendekia a , Mahfud Mahfud b a Program Studi Teknologi Rekayasa Kimia Industri, Politeknik Negeri Lampung, Bandar Lampung, Indonesia 35144 b Department of Chemical Engineering, Institut Teknologi Sepuluh Nopember, Surabaya, Indonesia 60111 * Corresponding author: yenivariyana@polinela.ac.id DOI: https://dx.doi.org/10.20961/equilibrium.v7i1.72842 Article History Received: 05-04-2023, Accepted: 26-05-2023, Published: 28-05-2023 Keywords: candlenut, RSM, MHG, yield ABSTRACT. Aleurites moluccana Willd, a known candlenut plant, has the potential to be used for vegetable oil, pharmacological purposes, and biofuel. However, there is a lack of knowledge on the optimal extraction conditions for this extraction. The current study aimed to use response surface methodology (RSM) to optimize the Microwave Hydro-diffusion Gravity (MHG) conditions for extraction yield. A three-factor-three-level Box-Behnken design (BBD) was used to investigate the effects of three independent parameters: material size (A), microwave power (B), and extraction time (C). The experimental data for the candlenut seed extraction were analyzed to obtain quadratic polynomial equations. The effects of various parameters on the yield of extraction yield were then examined and analyzed using plots and contours. The results showing extraction yield significantly influenced all independent parameters were p < 0.0001. Further, The study predicted the optimum conditions for extracting candlenut seeds, which included using a material size of 1.378 cm, microwave power of 599.359 W, and extraction time of 66.076 min, resulting in a yield of 5.015%. Based on experimental data conditions, the highest extraction yield was 5.5% of 1 cm, 600 W, and 60 min, respectively, which were in good agreement with the predicted model. The study concluded that the optimization using MHG method could be useful in industrial extraction processes. Further, the statistical methods can optimize the extraction process and reduce the number of experiments required. 1. INTRODUCTION The candlenut plant (Aleurites moluccana Willd) is a plant that belongs to the Euphorbiceae family. Candlenut originally came from Hawaii and then spread to several countries, including Indonesia [1]. In Indonesia, this plant is widely distributed almost throughout the entire region. The growth of candlenut plants in various regions has increased its production from year to year, making candlenuts a leading spice commodity and export product in Indonesia. Generally, candlenuts are exported to Singapore, Hong Kong, the United States, Australia, and Europe. Furthermore, the candlenut seed is the most economically valuable part of the plant, but its use in Indonesia is still limited to seasoning and partially exported in the form of whole or peeled seeds. Its use as a raw material for vegetable oil industries has not developed as much as in Japan, the Philippines, and some other countries. Candlenut seeds, which contain a high oil content of about 30% to 60%, are composed mainly of this oil [2], [3]. The oil mainly consists of unsaturated fatty acids characterized by a greater proportion of polyunsaturated acids (>89%) and also contains a very small amount of aromatic oils, such as essential oils [4], [5]. This means that candlenut seeds are quite potential as raw material for vegetable oil industries. In addition, the oil contained in candlenut seeds has many benefits, such as being used as a material for making soap, medicines, paints, cosmetics, and biofuels [1], [2]. Nevertheless, the methods that have been experimented with by researchers to extract oil from candlenut seeds are limited to the mechanical press method [6], Soxhlet extraction technology [7], and supercritical carbon dioxide (CO 2 ) extraction technology [8]. Therefore, the application of technology for extraction using microwaves can be reported based on this research. The advantage of microwave-assisted extraction is the minimization of the use of organic solvents, time efficiency, and environmentally friendly technology [9]–[11]. Additionally, the combination of gravity force and microwave-assisted extraction can increase the yield of candlenut oil extraction as aromatic oil. The Microwave Hydro diffusion and Gravity (MHG) method is a novel extraction method without distillation and evaporation processes, resulting in lower energy consumption [12]–[15]. Furthermore, the extraction method of MHG demonstrated exceptional outcomes across