Roasted sweet potatoes are a beloved winter snack for many, thanks to their nutty aroma and sweet flavor. However, have you ever encountered a bitter taste while enjoying one? If the bitterness isn’t just from burnt skin, it could be due to a diseased sweet potato. Particularly, black spots or an unpleasant taste can indicate a problem. Eating a diseased sweet potato may pose health risks as it might contain toxins. Knowing how to identify such potatoes and store them safely is essential. This guide explains the warning signs to watch for and proper storage techniques to enjoy sweet potatoes safely.

Bitter Taste in Sweet Potatoes: Could It Be Black Rot?

A bitter taste in sweet potatoes isn’t always from burnt skin—it could be a sign of black rot. Caused by the fungal pathogen Ceratocystis fimbriata, black rot enters through surface wounds. Affected sweet potatoes develop black spots on the surface and may also turn dark inside. Consuming such potatoes, even in small amounts, can be hazardous. If you taste bitterness, stop eating immediately and discard the potato.

Risks of Black Rot and Its Toxic Effects

Sweet potatoes with black rot produce a toxin called ipomeamarone, which can cause various symptoms such as:

• Loss of appetite
• Difficulty breathing
• Abdominal pain and diarrhea
• Severe cases may result in lung or liver damage

Removing the discolored parts is not enough, as the toxin may have already spread. It’s best to avoid eating infected sweet potatoes altogether.

How to Identify Sweet Potatoes Affected by Black Rot

Identifying diseased sweet potatoes can prevent accidental consumption. Key indicators include:

• Surface black spots: Small black dots or streaks appear, disrupting the smooth surface of a healthy potato.
• Dark discoloration inside: Cutting the potato reveals darkened areas, a clear sign of fungal infiltration.
• Bitter taste: A noticeably bitter flavor when chewing indicates possible contamination.

Even if only part of a potato appears diseased, it’s safest to discard it entirely. Check all nearby stored sweet potatoes for signs of infection.

Proper Storage Methods for Sweet Potatoes

Choosing the Right Sweet Potatoes

• Select unblemished potatoes: Avoid ones with visible cuts or injuries, as these allow pathogens to enter.
• Inspect the surface: Steer clear of sweet potatoes with black spots or unusual marks.
• Check for freshness: Choose firm, evenly colored sweet potatoes.

Optimal Storage Conditions

• Avoid refrigeration: Cold temperatures can damage the texture and reduce sweetness, increasing spoilage risks.
• Wrap in newspaper: Pack 2–3 sweet potatoes per bundle to maintain proper humidity and prevent fungal spread.
• Store in a cool, dark place: A well-ventilated area at 12–15°C is ideal. Keep away from direct sunlight.

Additional Tips for Safe Consumption

• Rotate sweet potatoes during roasting to ensure even cooking.
• Take a small bite to taste before fully eating—discard if bitterness is detected.
• Regularly inspect stored potatoes for signs of rot or infection, separating affected ones immediately.