Abstract:

In this paper, the extraction of anthocyanins from purple yam using acidified ethanol was optimized by response
surface methodology with Box-Behnken design. A quadratic polynomial model was established with Design-Expert 8.0.6
analysis software. At the same time, the ability of purple yam anthocyanins to scavenge hydroxyl and superoxide anion free
radicals was studied. Results indicated that the extraction yield of anthocyanins was influenced in decreasing order by the
following parameters: hydrochloric acid concentration, extraction time, ethanol concentration, solvent-to-solid ratio, and
temperature. Under the optimal conditions: 80 ℃, 3.5 h, a solvent-to-solid ratio of 25:1 (mL/g), and 70% ethanol with 18‰
hydrochloric acid at a volume ratio of 15:85, experiments led to an average extraction yield of 4.966 mg/g with a relative
standard deviation (RSD) of 0.29%, showing a relative error below 1.0% compared to the expected value. Purple yam
anthocyanins had a stronger free radical scavenging activity than vitamin C.

Key words: purple yam, anthocyanins, response surface methodology, extraction process, antioxidant