In winter, everyone will fall in love with hot roasted sweet potatoes. It's fragrant, sweet and irresistibly delicious. However, when it comes to sweet potatoes, everyone still has some questions. Common ones are: Will roasting sweet potatoes produce a large amount of acrylamide ? Will using air fryer to cook roasted sweet potatoes cause burns? What is the difference between purple potatoes and sweet potatoes? Can raw sweet potatoes be digested? Is it better to eat it steamed or grilled? Can people with diabetes eat roasted sweet potatoes? Will eating roasted sweet potatoes make you gain weight? I heard that sweet potatoes cannot be eaten on an empty stomach? Here I will tell you all the food knowledge related to sweet potatoes.
Knowledge point 1:
What pigment brings the color of sweet potatoes?
Sweet potato is a type of sweet potato. Sweet potatoes come in various skin and flesh colors, ranging from pure white, light yellow, orange to purple varieties, and are called white potatoes, yellow potatoes, sweet potatoes, purple potatoes, and even purple and white flower potatoes. Yellow and orange come from carotenoids , especially β-carotene ; while purple comes from anthocyanins , and the majority of anthocyanins are cornflower pigments.
Knowledge Point 2:
How much starch and sugar are there in sweet potatoes?
There are many varieties of sweet potatoes, some are particularly rich in starch, with a starch content as high as nearly 30%, but relatively little reducing sugar, which is suitable for extracting starch and making vermicelli; some have a starch content between 10% and 20%, but a relatively high reducing sugar content of 10%-20%, and have a sweet taste. Such sweet potatoes are suitable for fresh eating.
Knowledge Point 3:
Why are sweet potatoes sweeter in winter?
Soluble sugars are those sugars that can be dissolved in water, including glucose , fructose , sucrose, maltose , lactose and other small molecule sugars, and even fructooligosaccharides . All sugars that make people feel sweet are soluble in water. For fruits, vegetables and potatoes, the higher the soluble sugar content, the more delicious they are.
In winter, due to the lower temperature, plants will decompose part of the starch into soluble sugar in order to increase the osmotic pressure and resist the harm of low temperature and freezing. Therefore, after sweet potatoes are stored for a period of time in autumn and winter, the sugar content will increase significantly compared to when they were first harvested, making roasted sweet potatoes sweeter.
Knowledge Point 4:
Can sweet potatoes be eaten raw? Is it easy to digest?
The carbohydrates in sweet potatoes include, in addition to sugar, starch. From a digestion perspective, starch is usually divided into three parts: fast-digestible starch, slow-digestible starch and resistant starch .
Quickly digestible starch can be digested by the human body and can quickly increase blood sugar. For people with indigestion, quickly digestible starch can reduce the burden on the digestive system and provide them with energy faster. But for people who need to control blood sugar, eating too much quickly digestible starch at once will be a big test for their ability to control blood sugar.
Slowly digested starch can also be digested and can release energy slowly. However, because the digestion speed is slow, the rate of raising blood sugar is also slow, which is helpful for stabilizing blood sugar after meals.
Resistant starch has a high probability of not being digested and absorbed in the small intestine and will hardly increase blood sugar. Instead, it enters the large intestine and is decomposed and utilized by microorganisms to produce gas and short-chain fatty acids . A small amount of resistant starch has the benefit of improving intestinal flora and helping to control blood lipids . A large amount of resistant starch may cause gas production, bloating and indigestion problems.
You can also eat raw sweet potatoes. The reducing sugars in them can be digested. However, because of the high content of resistant starch, the proportion of ingredients that are difficult to digest is relatively high. It will raise blood sugar less after a meal. Eating too much will cause abdominal distension.
Knowledge Point 5:
Different cooking methods of sweet potatoes, will the speed of raising blood sugar and nutritional content be different?
A study found that steaming yellow-fleshed sweet potatoes in a pot for 35 minutes will slightly reduce the sugar content; while heating them in the microwave for 5 minutes will increase the sugar content. Boiling also increases the sugar content, but because some of the sugar dissolves into the water, it doesn't feel as sweet. Researchers believe that microwave heating may promote the degradation of starch and produce more glucose and maltose.
Therefore, when sweet potatoes are eaten cooked, most of the starch can be digested by humans, and the reducing sugar in them will increase the blood sugar response. In comparison, cooking and microwave cooking may raise blood sugar faster.
However, microwave cooking also has an unexpected benefit. After cooking, the content of carotene nearly doubled. In fact, this is not surprising, because it may be because the combination of carotene and protein is decomposed after microwave cooking and can be better released from the cells, so the actual amount obtained will increase.
Knowledge Point 6:
What are the nutritional differences between sweet potatoes of different colors?
Some scholars have found that the texture and taste of sweet potatoes are positively related to the content of β-carotene, protein and starch. In other words, for yellow-fleshed sweet potatoes, the more orange the color, the more delicious they are; for purple-fleshed sweet potatoes, the higher the anthocyanin content, the less delicious it is; the higher the sugar content, the more delicious it is.
analyzed the color and composition of 28 kinds of raw sweet potatoes and found that the total polyphenol content of purple sweet potatoes was significantly higher than that of yellow-fleshed varieties. Eating orange-fleshed sweet potatoes, like eating carrots, is a good way to supplement carotene. The
test also found that purple sweet potato has a strong inhibitory effect on the activity of trypsin , and the higher the content of polyphenol , the more effective it is in inhibiting protease . This can explain why purple sweet potatoes are prone to gastric congestion and bloating after eating too much, which is quite unfriendly to people with indigestion and gastrointestinal diseases.
Knowledge Point 7:
Do roasted sweet potatoes produce carcinogens? How much acrylamide does it contain?
Baked sweet potatoes, like baked potatoes , fried potatoes, etc., will produce acrylamide during cooking and processing above 120 degrees Celsius, with the largest acrylamide production at 160-180 degrees Celsius. This temperature range is exactly the temperature used when food is baked and fried. However, compared to French fries, the acrylamide content in baked sweet potatoes is still much lower.
Generally speaking, for the same food, if the degree of Maillard reaction is relatively high, the brown color will be heavier after cooking, and the texture will be crispier, the production of acrylamide will also be greater. Whether it's deep frying, oven, frying pan or air fryer, the principle is the same.
Acrylamide is not a highly toxic substance and will not significantly affect health when present in small amounts. Most residents in our country do not eat baked and fried dishes every day, nor do they eat bread, biscuits, cakes and other baked pasta every day. There is no need to worry about eating a roasted sweet potato occasionally.
Knowledge point 8:
Why do I feel dry in the mouth and sore in the throat after eating sweet potato chips baked in the air fryer? There may be two main reasons for this "fire reaction": First, baked food (including those cooked in an air fryer) has low moisture content. When eating, chewed dry food will absorb a large amount of moisture from saliva, oral mucosa and throat, causing local dehydration of the mucous membrane, dryness and discomfort. Dry and hard food fragments can easily cause small wounds to the mucous membrane. In addition, the resistance of the mucous membrane is reduced after dehydration, which can easily lead to bacterial infection and inflammation, resulting in pain and discomfort in the mouth and throat.
Second, grilled food will produce substances that promote inflammatory reactions during the high-temperature heating process, referred to as "pro-inflammatory ingredients." The crispier and browner the grilled food, the higher the content of these pro-inflammatory substances. If the temperature is too high, polycyclic aromatic hydrocarbons and substances and lipid oxidation polymerization products will also be produced, which are all things that promote inflammatory reactions. Eating too much pro-inflammatory ingredients can also induce acne or make acne more serious.
Finally, let me tell you how to make a quick, delicious and healthy roasted sweet potato, as well as some precautions:
1. Roast the sweet potato until it produces aroma and the surface turns yellow. Do not roast until it is brown, crispy and hard.
2. Sweet potatoes are harmless when cooked in a microwave oven. Cut the sweet potatoes into thick slices, place them in a microwaveable covered glass, ceramic, plastic box, or other container, add a spoonful of water to generate steam, and then heat over high heat for 6-8 minutes to steam. It is much faster than an ordinary steamer, and it operates on a regular basis, so no one needs to take care of it.
3. Steam the sweet potatoes first (either in a regular pot or in the microwave as above), then put them in an air fryer or a baking pan in the oven, spread them out and bake them. Air fryer at 180-200 degrees Celsius for 15-20 minutes, or oven for 30-45 minutes. In this way, you can quickly eat roasted sweet potatoes, which are sweeter and more delicious than traditional roasting methods.
4. For people who need to control blood sugar, steaming may be better. Compared with steamed sweet potatoes, roasted sweet potatoes require a longer heating time, are softer in texture, and have a high starch content that is quickly digested, which is not conducive to blood sugar control.
5. The softer, sweeter the texture, and the higher the sugar content, the sweeter and softer the roasted variety, the faster the blood sugar will rise after eating it. Baked sweet potatoes cannot be substituted for whole-grain beans.
6. People with hyperacidity should pay attention to eating less sweet potatoes, especially avoid eating large amounts before meals. Paired with other staple foods and vegetables, it is still okay to eat a small amount at a time.
In short, every food has its own advantages and disadvantages, and sweet potatoes are no exception. What impact does eating have on your health? As long as you experience it carefully, your body will naturally tell you.
Text/Fan Zhihong (Director of the Chinese Nutrition Society, chief scientific communication expert employed by the China Association for Science and Technology)
