What pots and containers can be used to bake delicious sweet potatoes?

Imagine that when we get off work and walk out of the subway entrance, the winter wind blows in our faces, but in this cold wind, because of the aroma of roasted sweet potatoes, the cold air seems to become sweet. Holding the hot roasted sweet potato in your hand, you can instantly dispel the coldness in your hand. After biting it open, the soft, sweet taste fills your mouth. Every bite is a love and enjoyment of this season.

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However, the "sweet potato assassin" that costs more than ten or twenty yuan always discourages us from buying it. So how can we bake sweet potatoes at home to make them fragrant and sweet?

01Microwave oven, oven, air fryer, who is the "king of baked sweet potatoes"?

Microwave ovens, ovens and air fryers are common small heating devices in our homes. Which one should we choose for baking sweet potatoes? Let's first understand how each of them works.

Microwave ovens transmit microwaves through food, causing the water molecules in the food to vibrate and generate heat . The heating speed is fast and relatively uniform, and the food can be heated in a short time with little water loss. Sweet potatoes baked in a microwave oven have a naturally cooked color, without obvious burn marks, and are soft and glutinous, with a delicate taste and high moisture content.

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The oven generates heat through heating elements (such as electric heating wires or heat pipes) , and then heats up the food through heat radiation and heat conduction . The temperature is high and the action time is long. The hot air circulation can make the temperature evenly distributed. The sweet potatoes baked in the oven are golden in color, with burnt spots on the skin and plenty of sugar caramel aroma. They taste crispy on the skin, soft and glutinous on the inside, and rich in layers.

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The air fryer heats food through the heating tube on the top and the high-speed circulating hot air, which generates hot air circulation and convection . The high-temperature hot air will dehydrate the surface of the food to form a crispy feeling, and the heating efficiency is high. The sweet potatoes baked in the air fryer have a golden and crispy surface, bright color inside, and taste both crispy and glutinous.

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02How to choose baking container?

Are there any particular containers for baking sweet potatoes? Not all the common plastic, ceramic and metal bowls in our homes can be used for high-temperature baking.

Different types of plastics have different heat resistance. Generally speaking, plastic bowls marked with "PS" (polystyrene) are prone to releasing toxic substances such as styrene monomer when heated at high temperatures for baking sweet potatoes . If these substances enter the human body, they may cause harm to our health, such as affecting the nervous system and endocrine system. Plastic bowls marked with "PP" (polypropylene) are more heat-resistant. Edible-grade PP can directly contact food and will not deform at high temperatures . However, although PP is relatively heat-resistant, it may also decompose small molecules when baked at high temperatures for a long time. Therefore, when buying plastic bowls, you should check whether the packaging is marked with "microwave safe" or "suitable for microwave ovens", indicating that the bowl has been specially treated and can be used in microwave ovens.

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According to different production processes, ceramic bowls can be divided into overglaze, in-glaze and underglaze. Overglaze is painted on the surface of ceramics, with bright colors and patterns protruding from the glaze. It usually feels less smooth and even has a convex feel on the edge of the picture; in-glaze is painted on the glaze after applying special glaze on the surface of ceramic vessels. The color is inside the glaze layer and there is no obvious concave and convex feeling; underglaze is painted on the unsintered porcelain blank and then glaze is applied. Finally, it is sintered at high temperature. The pattern is covered by a layer of transparent glaze film underneath, and the surface is bright, soft, smooth and not protruding. Overglaze and in-glaze ceramic bowls need to avoid hot food and heating appliances to prevent the release of toxic substances in high temperature environments. Underglaze ceramic bowls can withstand a certain high temperature. At normal baking sweet potato temperature, no harmful substances will be produced, but if they are suddenly transferred from a high temperature environment to a low temperature environment, there is a risk of cracking .

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Metal bowls or tin foil bowls made of food-grade metals such as stainless steel usually do not produce harmful substances during the baking process of sweet potatoes. The baking tray that comes with the oven is usually also made of metal, but metal has strong thermal conductivity and is easy to burn when taking it, so remember to wear heat-insulating gloves. It should also be noted that metal bowls cannot be used for microwave heating , because microwaves cannot penetrate metal and will be reflected back when encountering metal objects, thus blocking microwaves from heating food; and metal bowls will also absorb microwaves, excite electronic oscillations to generate large currents, which may cause electric sparks between the metal vessel and the furnace body. In severe cases, it may even damage the magnetron and other components of the microwave oven, causing the microwave oven to fail to work properly.

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03How to choose baking paper?

In addition to using bowls as baking containers, disposable food baking papers such as tin foil, aluminum foil, and silicone paper are becoming more and more popular among (lazy) people.

The main component of most tinfoil and aluminum foil on the market is aluminum. Since aluminum is a good conductor of electricity, when used in a microwave oven, microwaves will cause arcing on the metal surface, which may cause sparks, leading to fire or damage to the microwave oven. Therefore, tinfoil and aluminum foil are not recommended for use in microwave ovens , but they are fine for use in air fryers and ovens.

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Silicone oil paper is also a commonly used baking paper. It has a special three-layer structure: the first layer of base paper provides the basic physical strength and structural support of the paper; the second layer of solvent, the main components of which include polyethylene and modified polyolefin, plays a key role in connecting the base paper and silicone oil (in the regular production process, the solvent will be fully evaporated in two drying processes to ensure the safety of the final product); the third layer of silicone oil gives silicone oil paper unique anti-stick and high temperature resistance properties. Food-grade silicone oil is still stable at high temperatures, which can ensure the safety and effectiveness of paper during use. However, most silicone oil paper products are recommended to be used below 230 degrees and within 20 minutes . Within this temperature and time range, the various properties of silicone oil paper are best, and the migration of harmful substances can also be controlled within a safe range. When silicone oil paper exceeds its temperature resistance limit, carbonization reaction may occur to generate harmful substances such as polycyclic aromatic hydrocarbons.

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04DIY baked sweet potato strategy (stream saving version)

The microwave oven can bake sweet potatoes quickly, which is very suitable for busy office workers or students; the oven is suitable for people who like traditional baking methods; and the air fryer is more suitable for people who pursue a crispy taste. If you want the sweet potatoes to keep a soft and glutinous taste, you can use tin foil or aluminum foil to wrap the sweet potatoes to lock in the moisture of the sweet potatoes; if you like the sweet potatoes to have a caramelized taste on the surface, you can use silicone oil paper to evaporate the moisture on the surface of the sweet potatoes to form a crispy skin.

Finally, here is a super simple baked sweet potato tutorial:

Microwave sweet potatoes: Wash the sweet potatoes and wrap them in wet kitchen paper. Heat on high heat for 5-6 minutes, turn over and heat for another 5-6 minutes. Heat until the sweet potatoes are soft and cooked through.

Oven-baked sweet potatoes: Wash the sweet potatoes and preheat the oven to 200 degrees. Put the sweet potatoes in the oven and bake for 45-60 minutes, turning the sweet potatoes during the baking process. Bake until the surface of the sweet potatoes is golden and the inside is soft and glutinous.

Air fryer baked sweet potatoes: Wash the sweet potatoes, put them into the air fryer, and bake them at 200 degrees for 30-40 minutes, turning the sweet potatoes during the baking process. Bake until the surface of the sweet potatoes is golden and the inside is soft and glutinous.

No matter which method you choose, be sure to adjust the baking time appropriately according to the size of the sweet potatoes to bake fragrant and sweet sweet potatoes!

I wish everyone can eat hot baked sweet potatoes in this winter~

References
[1] Patent: Zhejiang Guanghe New Materials Co., Ltd. A silicone oil paper and its production process: CN202410662527.4[P]. 2024-07-26.

Author: Xu Yan, PhD candidate in Materials Science at Fudan University

Planning & Editing: Rain

Acknowledgements: Professor Ma Ruguang from the School of Materials Science and Engineering at Suzhou University of Science and Technology provided scientific guidance for this article.

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