18B-21 |
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C. C. TEOW, Dept. of Food Science, North Carolina State Univ., Box 7624, Raleigh, NC 27695-7624, V. -D. Truong, USDA-ARS and North Carolina State Univ., Dept. of Food Science, Box 7624, Raleigh, NC 27695-7624, R. F. McFeeters, USDA-ARS and NC State University, Department of Food Science, Box 7624, Raleigh, NC 27695-7624, and G. C. Yencho, Dept. of Horticultural Science, North Carolina State Univ., Box 7609, Raleigh, NC 27695-7609. Depending on the flesh colors (white, yellow, orange, purple), sweet potatoes can be a rich source of carotene, anthocyanins, and other phenolic compounds which are solubilized in lipophilic or hydrophilic solvents. However, most of the reported antioxidant activities in sweetpotatoes were only based on the hydrophilic fraction. In order to obtain the total antioxidant activity (TAA), the lipophilic fraction should also be considered. The objectives of this study were to determine the hydrophilic and lipophilic antioxidant activity of sweetpotatoes and their correlations with total phenolic and Β-carotene contents in different cultivars of sweetpotatoes. Freeze-dried powders of 5 sweet potato cultivars with varying flesh colors were extracted with hexane and acidified methanol. Antioxidant activity (trolox equivalent, TE 然/g fwb) was measured using three methods: oxygen radical absorbance capacity (ORAC), 2,2 diphenyl-1-picrylhydrazyl (DPPH), and 2,2'-azinobis(3-ethyl-benzothiazoline-6-sulfonic acid (ABTS). Total phenolics were measured using the Folin-Ciocalteau method, total anthocyanins by the pH-differential method, and Β-carotene by HPLC. The TAA value was highest (14.2 TE 然/g) for the purple-fleshed sweetpotato (FFP1), and lowest (1.6 TE 然/g) for Xushu18 (white-fleshed). The orange-fleshed lines (Hernandez, Beauregard, and NC98-608) had the TAA values of 5.4, 4.2 and 4.6 TE 然/g, respectively. The hydrophilic antioxidant activities (1.1 to 13.5 TE 然/g) were correlated with the total phenolic contents (r=0.98), and the lipophilic antioxidant activities (0.53 to 1.44 TE 然/g) were highly correlated with the Β-carotene contents, r=0.99. There were good correlations between ORAC and ABTS (r=0.96), as well as ORAC and DPPH (r=0.98), indicating that these methods have similar predictive capacity on sweetpotato antioxidant activities. Purple-fleshed sweetpotatoes have high total antioxidant activity, 80 mg/100 g fwb anthocyanins, and other phenolic compounds. These characteristics suggest that they are a healthy food for consumers, as well as a potential source for natural food colorants.
Session 18B, Food Chemistry: Antioxidant and bioactive agents
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |