Conventional and ultrasound-assisted extraction of rice bran oil with isopropanol as solvent

After cereal harvesting, rice is subjected to several milling processes to remove hull, germ, and bran and produce the final white rice. The bran represents around 10% of total grain weight and is usually considered as waste material. One of the most common rice bran applications is the extraction of rice bran oil, rich in γ-oryzanol, which has shown many health benefits including antioxidant, anti-inflammatory, and anti-hypercholesterolemic properties. Rice bran oil is usually extracted by organic solvents, which are toxic for health and the environment. In this work, rice bran oil was extracted through isopropanol extraction, and the best-operating temperature and bran to solvent ratio have been identified. After that, an ultrasound-assisted extraction was conducted at room temperature and with the same rice bran to solvent ratio of the isopropanol extraction. The kinetics evaluation through Peleg's model showed that the solvent extraction reaches the steady-state after 15 min while the ultrasound-assisted extraction reaches the steady-state after only 1 min producing very similar yields in rice bran oil and γ-oryzanol. Comparing these two green extraction techniques through a life cycle assessment, it has emerged that with the same amount of rice bran oil produced, the ultrasound-assisted extraction is the less environmentally impacting process. The room temperature ultrasound-assisted extraction allows minimizing the energy and time consumption demonstrating to be a sustainable process in line with the principles of green chemistry.