Why are sweet potatoes more fragrant and sweeter when roasted?

Wang Wenjie, intern reporter of Popular Science Times

On a cold winter day, eating a piece of hot roasted sweet potato warms your body and heart and is nutritious. Netizens exclaimed that "roasted sweet potatoes are simply a winter staple" and the topic "Why are roasted sweet potatoes tastier than steamed sweet potatoes" has also frequently appeared on the hot search list on Weibo. What is the secret of roasted sweet potatoes being sweeter than steamed sweet potatoes?

Wang Yanli, a weight management coach and registered dietitian of the Chinese Nutrition Society, said that the sweetness of sweet potatoes is directly related to the soluble sugar content. Studies have shown that baking sweet potatoes increases the soluble sugar content from 9.12% to 36.65%. Among them, maltose increases by 200 times, which may be the reason why baked sweet potatoes are sweeter.

Compared with steaming and boiling sweet potatoes, roasting sweet potatoes is more delicious because a large amount of furan and terpenoid compounds are produced during the roasting process. The production of furan is inseparable from the Maillard reaction. The reason why grilled meat, baked bread and pastries are delicious is also related to the Maillard reaction.

The reason why baked sweet potatoes are delicious is inseparable from the caramelization reaction. Wang Yanli explained that caramelization is a heat-induced chemical reaction that mainly involves the decomposition and reorganization of sugar substances when heated. This process is usually carried out at a relatively high temperature (160℃ to 210℃), and ultimately produces a variety of compounds, making the baked sweet potatoes ooze dark red sugar juice and more delicious. In life, caramel candies, baked goods, barbecued and fried foods, etc. also have caramelization reactions.

As for which way of eating is healthier? Wang Yanli said that both baked and steamed sweet potatoes have their own advantages. From a nutritional point of view, studies have shown that steamed sweet potatoes have an advantage in retaining carotenoids. From the perspective of the glycemic index (GI), steamed sweet potatoes have a lower glycemic index (GI is 44), while baked sweet potatoes have a higher glycemic index (GI is 94), which means that they can be quickly broken down into sugars, which may cause a short-term increase in blood sugar levels.

In terms of protein and fat content, there is no significant difference between the two.

Therefore, if you are concerned about the nutritional content, both cooking methods are acceptable and you can choose the specific method according to your taste and needs.