Abstract
Different-colored sweet potatoes have different contents of pigments and phenolic compounds in their root tubers, which influence the isolation of starch. It is important to justify the identification of the most suitable isolation medium of starch from different colored root tubers. In this study, starches were isolated from root tubers of purple, yellow and white sweet potatoes using four different extraction media, including H2O, 0.5% Na2S2O5, 0.2% NaOH, and both 0.5% Na2S2O5 and 0.2% NaOH. Their structural and functional properties were investigated and compared among different extraction media. The results showed that the granule size, apparent amylose content, lamellar peak intensity, thermal properties, and pasting properties were different among different-colored sweet potatoes due to their different genotype backgrounds. The four extraction media had no significant effects on starch structural properties, including apparent amylose content, crystalline structure, ordered degree, and lamellar peak intensity, except that the NaOH and Na2S2O5 treatment were able to increase the whiteness of purple and yellow sweet potato starches. The different extraction media had some effects on starch functional properties, including thermal properties, swelling power, water solubility, and pasting properties. The above results indicated that the H2O was the most suitable extraction medium to simply and fast isolate starch from root tubers of different-colored sweet potatoes.
Highlights
Sweet potato [Ipomoea batatas (L.) Lam.] is one of the world’s important starch-producing crops.Its dry root tuber contains 50 to 80% starch, and is rich in dietary fiber, vitamin C, provitaminA, iron, and minerals [1,2]
For starches extracted with H2 O, the color was significantly different among the three varieties
Starches were isolated from root tubers of purple, yellow and white sweet potatoes using H2 O, 0.5% Na2 S2 O5, 0.2% NaOH, and both 0.5% Na2 S2 O5 and 0.2% NaOH extraction media
Summary
Sweet potato [Ipomoea batatas (L.) Lam.] is one of the world’s important starch-producing crops.Its dry root tuber contains 50 to 80% starch, and is rich in dietary fiber, vitamin C, provitaminA, iron, and minerals [1,2]. Sweet potato [Ipomoea batatas (L.) Lam.] is one of the world’s important starch-producing crops. Its dry root tuber contains 50 to 80% starch, and is rich in dietary fiber, vitamin C, provitamin. Three commonly available sweet potato varieties have purple, yellow and white root tubers due to the different contents of phenolic compounds and pigments in their root tubers [3,4,5]. The purple sweet potato has a deep purple color due to the accumulation of anthocyanin. The anthocyanin produced in cytosol, a group of water-soluble flavonoids, is transported. The yellow sweet potato has a yellow color due to the accumulation of lipid-soluble β-carotene, which serves as the source of provitamin A showing vitamin A activity [5]
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