Extraction of seed oil from Diospyros lotus optimized using response surface methodology

Oil from seeds of Diospyros lotus was extracted using a conventional method with two different solvents: hexane and petroleum ether. A central composite design with response surface methodology were used to optimize the process. A second-order polynomial equation was employed, and ANOVA was applied to evaluate the impact of various operating parameters including extraction temperature (x1; 44.9–70.1 °C), extraction time (x2; 5.0–10.0 h) and solvent to solid ratio (x3; 11.6–28.4 mL g−1), on oil yield. Experiments to validate the model showed decent conformity between predicted and actual values. Extraction conditions for optimal oil yield were 61 °C, 8.75 h extraction duration and 19.25 mL g−1 solvent to solid ratio. Under these conditions, the oil yield was predicted to be 5.1340%. Oil samples obtained were then analyzed using gas chromatography. The fatty acid composition revealed the major fatty acids to be oleic acid (C18:1) and linoleic acid (C18:2). The analysis of oil also demonstrated a decent ratio between omega-3 and omega-6 fatty acids. The structure of seeds was imaged using scanning electron microscopy. Oil quality was analyzed thermogravimetrically and by Fourier transform infrared spectroscopy. The assigned nutritional features of the D. lotus oil suggested that it can be used as an edible oil in pharmaceutical and food industry in the future.