The reason why it is not recommended to eat too many baked sweet potatoes in winter is probably unexpected (not to make you fat)

Walking on the street in winter, as long as you pass by a place with roasted sweet potatoes, the smell is really "sweet". Although the winter in the north is very cold, as long as you eat a hot roasted sweet potato, it is really "warm in the body and sweet in the heart". The key is the unique fragrance that makes people drool along the nose.

If there is anything wrong with it, it is that you can't stop eating it once you start, and if you eat too much, you will easily fart. This is because sweet potatoes have a high dietary fiber content, which will be fermented by large intestine microorganisms to produce gas, causing bloating. Therefore, don't eat too much during work or at parties. Otherwise, it may be a little embarrassing.

Why are roasted sweet potatoes so fragrant?

A small oven can make sweet potatoes fragrant. Many people are curious about why sweet potatoes baked on the roadside are more "tempting" than those steamed in a steamer at home. The color, aroma and taste are a hundred times better than steamed sweet potatoes.

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Someone did do such a study. A total of 12 medium-sized sweet potatoes were prepared and randomly divided into four groups. One group was used as a control group and no treatment was given; the steaming group steamed the whole sweet potato in a dish for 40 minutes; the baking group baked the sweet potato in an oven at 200°C for 90 minutes; and the boiling group boiled the sweet potato in boiling water for 30 minutes. Then 10 people were invited to conduct sensory evaluations of each group. The results unanimously agreed that the baked sweet potato had the strongest aroma, the best taste, and the sweetest taste; the boiled sweet potato had a lower sweetness and aroma, and the worst overall taste.

In terms of sweet potato cooking methods, the types and concentrations of aromatic substances in roasted sweet potatoes are higher than those in steaming and microwaving. The color of the sweet potatoes will become darker, the tubers will lose more water, and the aroma will be richer.

The main reason is attributed to the wonderful reaction that occurs during the baking process of sweet potatoes. Sweet potatoes contain a large amount of carbohydrates. Thermal degradation of carbohydrates is the main way for cooked foods to form a large number of volatile aroma components, and the Maillard reaction and caramelization reaction are important reactions of thermal degradation. At the same time, it is also accompanied by some fat oxidation products, thermal release of glycoside terpenes, lipid and carotenoid degradation and some enzymatic reactions, etc., which makes the baked sweet potatoes produce a large amount of flavor substances, which is the main reason for the formation of its aroma.

1

Maillard reaction

During the process of roasting sweet potatoes, sweet potato starch is hydrolyzed into reducing sugars through the action of α-amylase and β-amylase. With the participation of protein and/or amino acids, the Maillard reaction will occur, giving the roasted sweet potatoes an attractive color. At the same time, a large amount of aldehydes, ketones, oxygen-containing heterocyclic compounds and other substances, such as furans, aromatic compounds, etc., will be produced.

2

Caramelization reaction

Due to the caramelization reaction, the color of the sweet potato skin and sweet potato flesh will gradually darken, producing a caramel flavor. The main types of sugars in sweet potatoes are fructose, sucrose, glucose, and maltose. The melting point of glucose is 146°C, fructose is 95°C, and maltose is 103°C, so fructose causes the fastest caramelization reaction.

3

Thermal degradation of fat

When heated above 150°C, most of the products are aldehydes and methyl ketones, while a certain amount of alkanes, fatty acids, alcohols and esters are also generated.

The flavor substances produced by these chemical changes play an important role in the formation of the aroma of roasted sweet potatoes. During the Maillard reaction and caramelization reaction, the content of heterocyclic aroma components produced accounts for a large proportion, mainly including cyclopentenones, furans, pyrans, etc., which give roasted sweet potatoes a roasted sweet aroma and a burnt sweet aroma.

In addition, when sweet potatoes are baked, the temperature is high, the starch granules in the cells gelatinize, expand in volume, exert pressure on the cell wall, destroy the cell wall structure, and gradually loosen the intercellular layer, which will cause the sweet potatoes to become soft and sticky. This is why baked sweet potatoes are more fragrant and softer than steamed sweet potatoes (click here for details → Why are baked sweet potatoes more delicious than steamed sweet potatoes? Someone has actually studied it).

Baked Sweet Potato Serving Guide

Whether baked sweet potatoes are delicious depends not only on the baking time and temperature, but also on the choice of the right sweet potato variety. Sweet potatoes with moderate starch content, high water content, and high sugar content taste better after baking. If you really can't tell the variety apart, choose those with yellow or orange flesh, which generally have lower starch content and taste sweeter than white flesh.

In addition, we have prepared a guide to eating baked sweet potatoes.

1

Street roasted sweet potatoes

Most of them are grilled over charcoal fire, which has an attractive aroma, but there are also safety issues. Traditional coal-baked sweet potatoes will produce sulfur dioxide and sulfur trioxide, which may cause sulfur and heavy metal pollution in the baked sweet potatoes. Studies have shown that in coal-baked sweet potatoes, both the sweet potato skin, the subcutaneous meat layer and the middle meat layer are contaminated by heavy metals, among which the sweet potato skin is the most polluted, followed by the subcutaneous meat layer, and the middle meat layer is the least polluted.

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Therefore, if you really can't resist the temptation of roasted sweet potatoes on the street, then choose roasted sweet potatoes with relatively intact skin and peel them before eating.

2

Baking sweet potatoes at home

If you are concerned about the safety of roasted sweet potatoes on the street, you can roast them at home in an oven or air fryer, which is just as delicious. The total content of aroma components in roasted sweet potatoes increases first and then decreases, and generally reaches the highest value after 45 minutes.

Oven: 200℃, 25 minutes, turn over and continue baking for 20 minutes; or bake directly at 180℃ for 45~60 minutes.

Air fryer: 200°C, bake for 35-45 minutes.

Taking into account that different ovens and air fryers have different tempers and sweet potatoes are of different sizes, you can observe more and adjust according to the situation.

3

Control eating

Although eating sweet potatoes regularly is good for health, the high dietary fiber content of sweet potatoes will be fermented by large intestine microorganisms to produce gas, causing bloating. In addition, eating too many sweet potatoes will also stimulate gastric acid secretion, and people with poor gastrointestinal function may have an uncomfortable reaction.

According to the recommendations of the "Dietary Guidelines for Chinese Residents", it is recommended that each person eat 50 to 100 grams of potatoes per day. If you choose to eat sweet potatoes, 100 grams of sweet potatoes is about the amount of one fist of an average woman, see the figure below.

Picture: About 100 grams of sweet potato (taken by myself)

4

This is a better match

Baked sweet potatoes have a high GI value. In order to stabilize blood sugar after a meal, it is recommended to eat them with vegetables and protein foods. Vegetables include tomatoes, cherry tomatoes, lettuce, fruit cucumbers, and Chinese cabbage; protein foods include egg custard, fried tofu, chicken legs, chicken breasts, and braised beef.

With the company of roasted sweet potatoes, I hope everyone can have a sweet and warm winter.

Tips:

Although baked sweet potatoes are "very delicious", they are actually a "blood sugar bomb". If you are not careful, your blood sugar will soar after eating them. This is mainly because during the baking process, the water content of the sweet potatoes will decrease, the total starch content will decrease, and gradually convert into monosaccharides and disaccharides, and the maltose content, which raises blood sugar faster, will increase rapidly.

Therefore, for people who want to lose weight and control blood sugar, not only should they eat less baked sweet potatoes, but it is also best not to eat baked sweet potatoes alone. Eating them with vegetables and protein foods is more conducive to stabilizing blood sugar after meals.

References

[1] Zhang, Rong, etal. "Impact of different cooking methodsson the flavor and chemical profile of yellow-fleshedtable-stocksweetpotatoes(IpomoeabatatasL.)." FoodChemistry:X 17(2023):100542.

[2] Tian Qing. Evaluation of aroma components and texture characteristics of baked sweet potatoes[D]. Hebei University of Science and Technology, 2021. DOI: 10.27107/d.cnki.ghbku.2021.000721.

[3] Zheng Meiling, Zhang Wenjie, Zhu Yuanyang, Feng Yanchuang, Xu Ruyan, Zhang Junsong. Dynamic changes in the content of main components and aroma components of Maillard reaction during sweet potato baking[J]. Freshness and Processing, 2021, 21(6): 85-92

[4] Zhao Junmei, Gao Xiaokuan, Hu Yaya, Han Meikun, Ma Zhimin, Mou Dehua. Research on the quality of fresh sweet potato varieties after baking[J]. Food Research and Development, 2021, 42(20): 1-7

[5]Bahado-Singh,PercevalSetal."RelationshipbetweenProcessingMethodandtheGlycemicIndicesofTenSweetPotato(Ipomoeabata tas)CultivarsCommonlyConsumedinJamaica."Journalofnutritionandmetabolismvol.2011(2011):584832.doi:10.1155/2011/584832

[6]https://glycemicindex.com/gi-search/?food_name=sweet+potato&product_category=&country=&gi=&gi_filter=&serving_size_(g)=&serving_size_(g)_filter=&carbs_per_serve_(g)=&carbs_per_serve_(g)_filter=&gl=&gl_filter=

[7]TsaiYJ,LinLY,YangKM,ChiangYC,ChenMH,ChiangPY.Effects of RoastingSweetPotato(IpomoeabatatasL.Lam.):Quality,Vola tileCompoundComposition,andSensoryEvaluation.Foods.2021;10(11):2602.Published2021Oct27.doi:10.3390/foods10112602

[8] Zhao Junmei, Wang Xueqing, Han Meikun, Hu Yaya, Gao Zhiyuan, Jiao Weijing, Liu Lanfu, Xin Guosheng, Yang Xue, Ma Zhimin, Mou Dehua. Evaluation of the best cooking methods for different types of sweet potatoes[J]. Journal of the Chinese Cereals and Oils Association, 2022, 37(8): 102-110

[9] Zhao Junmei, Gao Xiaokuan, Hu Yaya, Han Meikun, Ma Zhimin, Mou Dehua. Research on the quality of different varieties of fresh sweet potatoes after baking[J]. Food Research and Development, 2021, 42(20): 1-7

[10] Lu Haibo, Zhang Ling, Yin Lifang, Chi Meili, Chen Chuanqi, Ma Guifu. Contamination analysis and safety evaluation of baked sweet potatoes[J]. Food Science, 2011, 32(1): 229-231

Planning and production

Author: Xue Qingxin, registered nutritionist

Review丨Zhong Kai, Director of Kexin Food and Health Information Exchange Center