Bioactive and functional properties of purple sweetpotato (Ipomoea batatas (L.) Lam)

Antioxidant activity, antimicrobial effect, color potential, anthocyanin and phenolic content of purple sweetpotato and its sections were evaluated. Due to its high phenolic and anthocyanin content, sweetpotato has a high antioxidant activity. Antioxidant activity and total phenolic content were 3.2 and 2.5 times higher, respectively, than that of a blueberry variety assayed. Antioxidant activity in sweet potato skin was found to be almost 3 times higher than in the rest of the tissue. Sweetpotato extract at the tested concentration caused 40% inhibition on the growth of Salmonella Enteritidis, but no inhibition against Escherichia coli O157:H7. In the sweetpotato colorant preparation process, 99% of peroxidase activity was lost after 2 minutes of steam blanching. Colorant analysis indicates initial stability up to pH 5, even in the presence of oxygen. A pH 3 extract after 2 hours of exposure to 98degreesC was able to retain its intense monomeric anthocyanin color. Commercial red grape colorant was studied and found to be much less stable than the sweet potato extract analyzed. Characterization of bioactive and functional properties of novel crops opens the possibility to introduce new products into the market. The high phenolic content of purple sweetpotato seems to contribute to most of the bioactive and functional properties of this novel product. The high amount of anthocyanins in this crop makes it a healthier choice and an alternative for synthetic colorants, due to its high antioxidant activity and color stability.