Effect of acid-catalyzed methanolysis on the bioactive components of rice bran oil

The change in bioactive components in oil derived from rice bran oil after acid-catalyzed methanolysis was investigated in this study. The effects of catalyst amount, molar ratio of methanol to oil, reaction time, and nitrogen purging on acid-catalyzed methanolysis were investigated to find the optimum condition in converting all free fatty acids and acylglycerides into biodiesel with minimum loss of bioactive components. Acid-catalyzed esterification at 60 °C using 5 wt% of sulphuric acid as the catalyst can convert all free fatty acids (initial content = 59.19%) and acylglycerides (initial content = 19.31%) into fatty acid methyl esters in 5 h with a molar ratio of methanol to oil = 40. After the reaction, the losses of squalene, α-tocopherol, γ-tocotrienol, campesterol, stigmasterol, β-sitosterol, and γ-oryzanol are 50.07%, 18.06%, 63.09%, 21.68%, 28.74%, 25.42%, and 35.43%, respectively. When nitrogen purging was applied during the reaction, the losses of the aforementioned bioactive components became 42.54%, 0.00%, 43.47%, 23.47%, 26.66%, 24.07%, and 29.76%, respectively. In addition, oxidation products were not detected by GC-MS during acid-catalyzed methanolysis. From the present investigation, loss of bioactive components can be mitigated by carried out the reaction under nitrogen atmosphere.