Sweet potatoes are a popular root vegetable known for their sweet, starchy flavor and bright orange flesh. However, when cutting open a sweet potato, you may notice some brown spots or streaks on the interior of the root. What causes these brown spots and are they safe to eat? Here’s a closer look at the brown spots inside sweet potatoes.
What Causes the Brown Spots?
The brown spots or streaks found inside sweet potatoes are caused by the accumulation of chlorogenic acid. Chlorogenic acid is a natural compound found in sweet potatoes that acts as an antioxidant. It is one of the main phenolic acids found in sweet potatoes and is thought to contribute to some of their health benefits.
Chlorogenic acid tends to accumulate in small pockets throughout the sweet potato, leading to the development of brown spots or streaks on the interior flesh. This buildup occurs more frequently in certain varieties of sweet potato.
For example, orange-fleshed sweet potato varieties tend to have more noticeable brown spotting than white-fleshed or yellow-fleshed varieties. The Bronzed Garnet and Hernandez sweet potato varieties are two types that frequently have abundant interior brown spotting.
The development of these chlorogenic acid-rich spots is not an indication that the sweet potato is spoiled or defective in any way. It is a natural part of the sweet potato root as it matures.
Are the Brown Spots Safe to Eat?
The brown spots inside of sweet potatoes are completely safe and edible. The chlorogenic acid that accumulates in these regions does not pose any health risks.
Chlorogenic acid is found throughout the sweet potato root, but simply builds up in higher concentrations in some areas leading to visible spotting. It does not affect the flavor or texture of the sweet potato flesh.
In fact, chlorogenic acid is linked to some potential health benefits. As an antioxidant, chlorogenic acid may help protect cells against oxidative damage. It also has anti-inflammatory effects and may play a role in stabilizing blood sugar levels.
Eating the brown spots along with the rest of the sweet potato will provide all the nutritional benefits that this root vegetable has to offer. The spots can be eaten raw or cooked.
Do the Brown Spots Affect Sweet Potato Quality?
The presence of interior brown spots does not indicate anything about the quality or freshness of a sweet potato. These harmless spots have no impact on the taste, texture, or nutrition of the root.
Sweet potatoes that are moldy, shrivelled, discolored on the surface, or showing signs of sprouting should be avoided. However, smooth, firm sweet potatoes with brown spotting inside are perfectly fine to purchase and eat.
If anything, the abundance of chlorogenic acid in these spotted regions may provide an extra boost of antioxidants when consuming the entire root.
How to Store Sweet Potatoes with Brown Spots
Sweet potatoes with brown spots can be stored just like any other fresh sweet potato:
- Store whole, unwashed sweet potatoes in a cool, dark place. The ideal storage temperature is between 55-60°F.
- Do not refrigerate raw sweet potatoes. The cold air can negatively affect the flavor and texture.
- Place sweet potatoes in a basket or perforated plastic bag. Avoid sealing them in an airtight container.
- Cooked mashed sweet potatoes can be refrigerated for 3-5 days.
Proper curing after harvest extends the shelf life of fresh sweet potatoes. Well-cured, whole sweet potatoes can last 2-3 months when stored correctly.
Signs that a sweet potato has gone bad include mold growth, wrinkling, sprouting, and dark or soft surface spots. At the first signs of spoilage, cook the sweet potato right away or discard it if the decay is too advanced.
Uses for Sweet Potatoes with Brown Spots
Sweet potatoes exhibiting internal brown spots can be used in any recipe calling for fresh sweet potatoes. The spots do not affect the flavor or texture once cooked.
Here are some delicious ways to use sweet potatoes with spots:
- Roasted: Cut into wedges, toss with oil and seasonings, and roast at 400°F until tender.
- Pureed: Boil and mash with butter, milk, cinnamon, and maple syrup.
- Baked: Pierce whole sweet potato, bake at 375°F, and serve with butter.
- Fried: Cut into spears or rounds, coat in batter, and fry until crispy.
- In soup: Dice and add to chicken, squash, or bean-based soups.
- As chips: Slice very thinly, coat with oil, and bake until crispy.
The brown spots are not visible once the interior flesh is exposed and cooked. The chlorogenic acid also breaks down with heat, so any impact on flavor or color dissipates with cooking.
Are Brown Spots More Nutritious?
Since the brown spots contain a higher concentration of chlorogenic acid, they may pack a more concentrated dose of antioxidants. However, the levels of other nutrients in the spots versus the surrounding flesh are likely minimal.
Overall, sweet potatoes with and without abundant brown spotting have very similar nutritional profiles. They are both excellent sources of:
- Vitamin A: Needed for immune function and vision.
- Vitamin C: An antioxidant that supports immune health.
- Potassium: Helps regulate fluid balance and heart function.
- Fiber: Promotes digestive and heart health.
Some early studies suggest the antioxidant activity of chlorogenic acid may help reduce oxidative stress in the body. More research is needed to determine if this translates to any significant health impacts for humans.
For now, it is safe to say that brown spots do not reduce the nutritional quality of a sweet potato. Their presence simply provides a small boost in one particular antioxidant compound.
How to Prevent Brown Spots in Sweet Potatoes
Since the brown spots are natural rather than detrimental, there is no need to try to prevent their development in sweet potatoes. However, some steps may result in fewer spots:
- Select other varieties. Yellow and white sweet potato varieties show less spotting.
- Grow your own. Homegrown sweet potatoes tend to have fewer spots.
- Cure properly after harvest. Well-cured sweet potatoes resist spotting during storage.
- Avoid injury and bruising. Damage can increase spotting over time.
Keep in mind even with these preventative measures, some brown spots may still develop. This is perfectly normal for healthy, mature sweet potato roots.
What About Other Color Spots?
While small brown spots are normal for sweet potatoes, spots of other colors may be a sign of underlying issues:
- Dark brown or black spots – These very dark, sunken spots can indicate fungal decay or chilling injury.
- Soft, mushy spots – Indicative of bacterial or fungal rot setting in.
- White spots – Can develop after harvest due to calcium deficiency.
- Dark purple spots – Related to low temperatures or incorrect curing.
Spots that are discolored, sunken in, or accompanied by soft, mushy areas suggest the sweet potato is past its prime. Unless these issues are very minimal, it is safest to discard damaged sweet potatoes.
Conclusion
The development of small brown spots or streaks inside a sweet potato root is completely normal. These spots are caused by an accumulation of chlorogenic acid and do not negatively impact the flavor, texture, or nutrition of the sweet potato flesh. The brown spots can be eaten along with the rest of the sweet potato. Storing, cooking, and consuming sweet potatoes with interior brown spotting is perfectly safe and provides all the nutritional benefits you would expect from this versatile root vegetable.