Abstract:

The objective of this study was to explore the simultaneous preparation of anthocyanins as well as the byproducts
starch, cellulose and protein from purple sweet potato. ‘Violet’ purple sweet potato was mixed with acid ethanol (pH 2)
and then crushed. After filtration of the mixture, the filtrate was precipitated to obtain starch, and the filtration residue
was combined with the supernatant left after starch precipitation and extracted by a microwave-assisted solvent extraction
technique to obtain anthocyanins. Purple sweet potato protein was precipitated from the extract and cellulose was obtained
from the extraction residue. The optimal conditions for microwave-assisted extraction of anthocyanins were determined as
microwave irradiation for 4 min, extraction at 52 ℃, and 62% aqueous ethanol adjusted to pH 2 as the extraction solvent at a solidto-
solvent ratio 1:22.40 (g/mL), leading to an extraction yield of (93.64±0.69)% and an anthocyanins content of (9.58±0.20) mg/g
in the extract. The purity of the starch product was (95.77±0.41)% and (73.06±1.03)% of the total starch was obtained. The dried
filtration residue contained (117.11±2.69) mg/g cellulose. The purity of the protein product was (524.78±24.84) mg/g. With this
preparation technique, better utilization of purple sweet potato could be achieved at lower costs.

Key words: purple sweet potato, microwave, anthocyanins, starch, protein