53. Roasted Sweet Potato (군고구마)


Roasted sweet potatoes, also known as “gun-goguma” in Korean, hold a special place in many people’s hearts for their delicious taste and nostalgic appeal. Despite the changing times, the tradition of roasting sweet potatoes lives on, with vendors selling them on small, round stones at convenience stores, reminiscent of the past when they were roasted in large drums with ear-covering hats. But what makes roasted sweet potatoes tastier than their steamed counterparts? Beyond nostalgia, the answer lies in science.

Sweet Potato
Barrel of baked sweet potatoes


1. Sweet Potato Chemical Process:

Sweet potatoes primarily consist of carbohydrates, with starch being the main component. Starch, composed of multiple glucose units, does not provide a sweet taste due to its large size. However, when sweet potatoes are roasted or cooked, an enzyme called beta-amylase is released, breaking down starch into maltose, a disaccharide form of glucose. Maltose contributes to the sweetness of roasted sweet potatoes, similar to the sweetness found in traditional Korean beverages like sikhye and malt syrup.

Roasted Sweet Potato
Roasted Sweet Potato

2. β-Amylase Activity:

To maximize the sweetness of sweet potatoes, it’s essential to generate a significant amount of maltose. For starch to be efficiently converted into maltose, beta-amylase needs to remain active for an extended period. Roasting sweet potatoes allows beta-amylase to function for a longer duration compared to steaming. The optimal temperature for beta-amylase activity ranges from 55 to 65 degrees Celsius. Roasting sweet potatoes slowly raises the internal temperature, maintaining it around 60 degrees Celsius for an extended period. In contrast, steaming sweet potatoes accelerates the process, leading to the rapid degradation of beta-amylase.

3. Roasting Methods:

Roasting sweet potatoes at home can be achieved using various methods. Setting an oven to around 60 degrees Celsius and slowly roasting them is one option. Alternatively, placing clean small stones in a pot or kettle, then roasting sweet potatoes on top, can also yield delicious results.

Setting an oven to around 60 degrees
Setting an oven to around 60 degrees

4. Health Considerations:

While roasted sweet potatoes are undeniably delicious, it’s essential to consume them in moderation, considering their impact on blood sugar levels. Roasted sweet potatoes, with their higher maltose content, have a significantly higher glycemic index compared to steamed sweet potatoes. According to a joint publication by the Rural Development Administration and Kyung Hee University, the glycemic index of roasted sweet potatoes is 90.9, much higher than the 70.8 of steamed sweet potatoes. The glycemic index measures how quickly a particular food raises blood sugar levels, taking into account the amount consumed.

5. Balanced Consumption:

Enjoying roasted sweet potatoes as part of a balanced diet can provide a delightful indulgence without compromising health. Pairing them with protein or fiber-rich foods can help mitigate their impact on blood sugar levels and ensure a more balanced meal.

6. Cultural Significance:

Beyond their taste and nutritional value, roasted sweet potatoes hold cultural significance, evoking memories of simpler times and cherished traditions. They serve as a reminder of the importance of preserving culinary heritage and passing it down through generations.

7. Nutritional Profile:

Sweet potatoes, whether roasted or steamed, offer a host of nutrients, including vitamins A and C, potassium, and fiber. Despite the differences in sweetness, both forms provide valuable micronutrients that contribute to overall health and well-being.

8. Variety and Preparation:

Roasted sweet potatoes come in various shapes, sizes, and varieties, each offering a unique flavor profile. Experimenting with different types of sweet potatoes and preparation methods allows for culinary exploration and enjoyment.

9. Sustainability:

Supporting local farmers and choosing sustainably sourced sweet potatoes can contribute to environmental conservation efforts and promote eco-friendly practices. By opting for locally grown produce, consumers can reduce their carbon footprint and support community livelihoods.

10. Enjoying the Experience:

Whether enjoyed alone on a crisp autumn day or shared with loved ones around a bonfire, the experience of roasting and savoring sweet potatoes goes beyond mere consumption. It encompasses moments of joy, connection, and appreciation for nature’s bounty.


In conclusion, the appeal of roasted sweet potatoes lies not only in their delicious taste but also in the scientific processes that enhance their sweetness. Understanding the chemical reactions that occur during roasting sheds light on why roasted sweet potatoes are favored over steamed ones. While indulging in this beloved treat, it’s essential to be mindful of portion sizes and balance them with other nutritious foods to maintain overall health and well-being.


What is the optimal temperature for roasting sweet potatoes?
The optimal temperature for roasting sweet potatoes is around 60 degrees Celsius, allowing for prolonged beta-amylase activity and the conversion of starch into maltose.

Are roasted sweet potatoes healthier than steamed ones?
While both roasted and steamed sweet potatoes offer nutritional benefits, roasted sweet potatoes have a higher glycemic index due to their increased maltose content, which may impact blood sugar levels more significantly.

Can roasted sweet potatoes be part of a balanced diet?
Yes, roasted sweet potatoes can be enjoyed as part of a balanced diet when consumed in moderation and paired with protein or fiber-rich foods to mitigate their impact on blood sugar levels.

Are there different varieties of sweet potatoes suitable for roasting?
Yes, various varieties of sweet potatoes are suitable for roasting, each offering unique flavors and textures. Experimenting with different types can enhance culinary experiences.

How can I ensure the sustainability of sweet potatoes?
Choosing locally grown sweet potatoes from sustainable sources supports environmental conservation efforts and promotes eco-friendly practices in agriculture.

Can roasted sweet potatoes be enjoyed year-round?
Yes, roasted sweet potatoes can be enjoyed year-round, providing a versatile and nutritious option for meals and snacks.

Are there any cultural traditions associated with roasting sweet potatoes?
Yes, roasting sweet potatoes holds cultural significance in many societies, often evoking memories of family gatherings, festivals, and cherished traditions.

What are the key nutrients found in sweet potatoes?
Sweet potatoes are rich in vitamins A and C, potassium, fiber, and other essential nutrients, making them a valuable addition to a healthy diet.

Can roasted sweet potatoes be included in weight management plans?
Yes, when consumed in moderation as part of a balanced diet, roasted sweet potatoes can contribute to weight management goals due to their fiber content and satiating properties.

Are there any alternative methods for roasting sweet potatoes at home?
Yes, besides using an oven, sweet potatoes can be roasted on clean stones placed in a pot or kettle, offering a traditional and flavorful cooking method.

Today’s Quiz

What enzyme is responsible for breaking down starch into maltose during the roasting of sweet potatoes?
a) Alpha-amylase
b) Beta-amylase
c) Amylase
d) Maltase

Answer: b) Beta-amylase


Rural Development Administration (RDA)
Kyung Hee University
Harvard T.H. Chan School of Public Health
American Diabetes Association
Food and Agriculture Organization of the United Nations (FAO)

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