What are the nutritional benefits of yellow, white and purple sweet potatoes? A detailed explanation of the differences in their nutritional composition
What are the nutritional differences between yellow, white and purple sweet potatoes, and which is better? Sweet potato planting time and methods - you can also look into it yourself! Divided by the color of the flesh inside the root, sweet potatoes can be roughly classified into three types: white-fleshed, yellow-fleshed (orange, red)
What are the nutritional differences between yellow, white and purple sweet potatoes, and which is better? Sweet potato planting time and methods, you can also look into it yourself!
Divided by the color of the flesh inside the root, sweet potatoes can be roughly classified into three types: white-fleshed, yellow-fleshed (orange, red) and purple-fleshed. The white type has a very low pigment content; the yellow type contains varying amounts of carotenoids, including β-carotene; the purple type contains anthocyanins, but basically no carotenoids.
So, what exactly are the nutritional differences between sweet potatoes of different colors?
1. White-fleshed sweet potato —— the "champion" of starch
The characteristics of white-fleshed sweet potatoes are:
—— The root has a high starch content, reaching about 25% of fresh weight, while the content of fructose, glucose, sucrose and crude protein is relatively low. Precisely because the starch content is especially high, it is very suitable as a starch raw material for industrial alcohol fermentation (because calculated by starch content, it is even cheaper than rice and white flour).
—— The content of phytochemicals such as flavonoids and polyphenols is relatively low (about 50% and 20% of that in yellow-fleshed and purple-fleshed roots, respectively). The anthocyanin content is basically zero, the total carotene content is significantly lower than that of yellow-fleshed varieties, and the contents of Fe, Zn, Ca and K are all relatively low.
Overall, compared with varieties of other colors, the health advantages of white-fleshed sweet potatoes are not so obvious. A friendly reminder: because of its high starch content, when converting it into rice you cannot use a 4:1 ratio; it should be 3:1.
2. Yellow-fleshed sweet potato —— the "queen" of carotenoids
The characteristics of yellow-fleshed sweet potato roots are:
—— Higher sugar content and greater sweetness. Because yellow-fleshed sweet potatoes are high in sugar, roasted sweet potatoes taste sweeter; because they have less starch, the texture is not so dry and is relatively soft. At the same time, because the soluble sugars and a small amount of protein in them can take part in the Maillard reaction and caramelization reaction, the roasted sweet potato has a rich aroma, giving off an alluring caramelized fragrance.
—— High carotenoid content. The yellow and orange colors of yellow-fleshed sweet potatoes come from carotene; the deeper and more intense the color, the higher the carotene content. Researchers at the Sweet Potato Research Institute found that the variety "Zheshu 255" has the highest total carotene content, reaching 46.1mg/100g dry weight (converted to fresh weight it is also as high as 10mg/100g, no less than carrots!).
Among carotenoids, β-carotene can be converted into vitamin A in the human body and plays an important role in preventing vitamin A deficiency and protecting eyesight. α-carotene is beneficial for the prevention of cardiovascular and cerebrovascular diseases and cancer, while carotenoids such as lutein that cannot be converted into vitamin A are beneficial for the health of the retina and the heart.
3. Purple-fleshed sweet potato —— the "king" of anthocyanins
The characteristics of purple-fleshed sweet potato roots are:
—— Less starch and more protein. Compared with white-fleshed and yellow-fleshed sweet potato varieties, purple sweet potatoes have a slightly lower starch content, but a higher protein content (calculated by dry weight, 2.3 times that of yellow-fleshed and 6.6 times that of white-fleshed). Their sugar content varies by variety; some are very sweet and soft, while others are relatively more mealy.
—— Richer in antioxidants and trace elements. As introduced in a previous WeChat article, the purple color of purple sweet potatoes is not caused by genetic modification or dyeing, but by their relatively high anthocyanin content, so purple sweet potatoes are a rich and inexpensive source of anthocyanins (their cost-effectiveness for anthocyanins is more than 5 times that of blueberries). Anthocyanins have antioxidant effects, protect the liver, improve gut microbiota and more, and are especially beneficial for the health of the skin and eyes.
In addition, compared with white and yellow sweet potatoes, purple sweet potatoes have an advantage in the content of trace elements such as Fe, Zn and Mg, and their total content of flavonoids and polyphenols is significantly higher than that of white-fleshed and yellow-fleshed varieties. Because of these advantages, purple sweet potatoes have gradually become popular in the market in recent years.
In short, white sweet potatoes, yellow sweet potatoes and purple sweet potatoes, the members of the sweet potato family, each have their own characteristics and strengths. For everyday diet, whether yellow-fleshed or red-fleshed sweet potatoes, they are very suitable for regular consumption in daily meals. Being rich in dietary fiber and potassium and containing vitamin C are also advantages they share. According to the 2016 edition of the Chinese Dietary Guidelines, the recommended daily intake of grains and potatoes is 250-400g, of which whole grains and mixed beans are 50-150g, and potatoes are 50-100g.
