The reaction efficiency of soybean oil transesterification in supercritical ethanol in a continuous catalyst-free process was investigated under different water concentrations. Experiments were performed at 350 °C and 20 MPa, with an oil/ethanol ratio of 1:40. A fatty acid ethyl ester content of 77.5% was obtained at a flow rate of 1.5 mL/min in a water-free system, while the maximum concentration of ethyl esters reached for a water content of 10 wt % was 68.1% at a flow rate of 1.0 mL/min. Decomposition and trans-isomerization of unsaturated fatty acids were significantly affected by the flow rate, with a pronounced reduction in the ratio of C18:2/C16:0 in the final product compared to the starting oil.

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This work investigated the effect of temperature on the reaction efficiency of soybean oil transesterification in supercritical ethanol in a continuous catalyst-free process under different water concentrations and at varying substrate flow rates. Experiments were performed in the temperature range from 250 to 325 °C, at 20 MPa, with an oil to ethanol molar ratio of 1:40. Results showed that temperature and substrate flow rates strongly affected the reaction conversion to fatty acid ethyl esters, decomposition, and trans-isomerization of unsaturated fatty acids, mainly for C18:2 and C18:3. It is shown that the synthesis of esters was favored by the addition of water to the reaction medium and the degradation phenomenon decreased as water concentration increased from 0 to 10 wt %.

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The objective of the present study was to evaluate ultrasound-assisted extraction (UAE) to obtain oil from chia seeds (Salvia hispânica L.). A Box-Behnken design was applied to investigate and optimize the process variables (temperature, solvent to seed ratio and time) for oil yield. The solvent to seed ratio and temperature had the greatest influence on oil yield, followed by the extraction time (P < 0.05). An extraction temperature of 50C, a solvent to seed ratio of 12 mL/g and 40 min of extraction were identified as the optimal conditions, with 27.24% oil yield. The application of ultrasound resulted in higher oil yield when compared with the process without ultrasound (P < 0.05). The fatty acid composition extracted by UAE was similar to that of oil extracted using other extraction methods. Linolenic acid (∼66%) and linoleic acid (∼20%) were the main fatty acid constituents of chia seed oil. The quantity of unsaturated fatty acids was higher than saturated fatty acids.