Abstract:

Objective: To explore the optimal ultrasonic-assisted extraction conditions of pigment from sorghum flour and
evaluate the antioxidant activity of the extracted pigment. Methods: Based on the single-factor designs, the ultrasonicassisted
extraction conditions of pigment from sorghum flour were optimized by response surface methodology with Box-
Behnken design in order to increase the extraction yield of pigment. Meanwhile, the in vitro antioxidant activity of pigment
from sorghum flour was also studied. Results: The optimal extraction conditions were 50.76%, 500.64 W and 1:16.72 (g/mL)
for ethanol concentration, ultrasonic power and material/liquid ratio, respectively. Under these conditions, the maximum
predicted extraction yield of pigment was 54.26%. When the ethanol concentration, ultrasonic power and material/liquid
ratio were 51%, 504 W and 1:17 (g/mL), respectively, the experimentally observed extraction yield of pigment was
(53.99 ± 0.26)%. Sorghum pigment showed significant scavenging effects on 1,1-diphenyl-2-picryl-hydrazy (DPPH·) and
hydroxyl free radicals (·OH) and excellent reducing power. Conclusion: Response surface methodology with Box-Behnken
design is applicable for the optimization of the ultrasonic-assisted extraction of pigment from sorghum flour. The pigment
from sorghum flour has strong antioxidant capacity.

Key words: sorghum pigment, ultrasonic-assisted extraction, response surface methodology, antioxidant activity