Why it's (almost) impossible to make Crispy Sweet Potato Fries in the oven.

Summary by Krater

This video explains the science behind why sweet potatoes are difficult to crisp up in the oven and demonstrates a technique involving boiling with vinegar and tossing in a cornstarch slurry to achieve crispy oven-baked sweet potato fries.

From the video

Answers: How do you make crispy sweet potato fries in the oven?

• Sweet potato chemistry
• Starch vs sugar in potatoes
• Amylase enzyme activity
• Pectin and boiling in vinegar
• Cornstarch slurry technique
• Low-oil oven baking

Ingredients

• 4 sweet potatoes
• salt
• vinegar
• 50 g cornstarch
• 80 g cold water
• peanut oil
• black pepper

What it concludes

• Sweet potatoes contain much more sugar than regular russet potatoes, and their high sugar content prevents them from crisping up.
• The amylase enzyme in sweet potatoes converts up to 75% of starch into sugar when heated between 135 and 170 degrees Fahrenheit.
• Boiling sweet potato fries in water with a splash of vinegar limits starch breakdown by slowing down pectin degradation and gelatinizing surface starches.
• Tossing boiled sweet potato fries in a cornstarch slurry before baking creates a gelled coating that results in a crispy crust using very little oil.