Abstract:

Ultrasonic-assisted extraction was used to extract essential oil from millet bran. The effects of extraction solvents,
solid-to-liquid ratio, extraction temperature and repeated extraction cycles and extraction duration, ultrasonic frequency and
ultrasonic power on the yield of millet bran oil were investigated by using one-factor-at-a-time and orthogonal array designs.
The results showed that the optimal extraction conditions were determined as follows: n-butyl alcohol as extraction solvent,
solid-to-liquid ratio of 1:10 (g/mL), two repeated cycles of extraction at 60 ℃ for 20 min, ultrasonic frequency of 40 kHz
and ultrasonic power of 300 W. Under these conditions, the yield of millet bran oil was 87.68%. The major fatty acids of
millet bran oil were 13.08% hexadecanoic acid, 56.73% 9,12-octadecadienoic acid, 19.78% 9-octadecenoic acid, and 5.41%
octadecanoic acid, as demonstrated by GC-MS analysis. Additionally, 0.8% β-sitosterol was also detected. These results
indicate that the millet bran oil is a healthy and nutritional cooking oil.

Key words: millet bran oil, ultrasonic-assisted extraction, process, orthogonal array design, gas chromatography-mass spectrometry