If you’ve ever reached into your potato bin and noticed white spots on potatoes, you’re not alone. This is a very common storage condition issue that many gardeners and home cooks encounter. These spots can look a little strange, but understanding what causes them is the first step to preventing them and keeping your spuds in perfect shape.
This guide will explain exactly what those white spots are, whether they’re safe to eat, and how you can store your harvest to avoid them in the future. With a few simple changes, you can enjoy firm, spot-free potatoes for months.
White Spots On Potatoes
Those white spots you see are almost always a sign of moisture loss. They are not mold or a disease in the traditional sense. Instead, think of them as a kind of bruise or stress mark caused by less-than-ideal storage enviroments.
What Are These White Spots Exactly?
The white spots are areas where the potato has started to dehydrate. Potatoes are about 80% water. When they lose moisture from specific points, the starch and cells in that area collapse and form a dry, chalky spot. This is often called “pressure bruising” or “high sugar spot.”
- Pressure Bruising: Caused by potatoes being stacked to high or having heavy weight on top of them. The pressure damages cells, forcing moisture out.
- High Sugar Spots: Sometimes linked to temperature fluctuations, which cause sugars to concentrate in certain areas, leading to a dry, white patch.
Are Potatoes with White Spots Safe to Eat?
Yes, in the vast majority of cases, potatoes with these white spots are perfectly safe to eat. The affected area is simply dehydrated. Here’s what you should do:
- Feel the spot. If it’s dry and firm, it’s just a moisture bruise.
- Use a paring knife to gently scrape or cut away the spot. The potato underneath is usually normal.
- If the spot is soft, mushy, or has an odd smell, cut deeper to remove it, as it might be starting to decay.
Always cook potatoes thoroughly, as you normally would. The white spots themselfs won’t affect flavor in a significant way, though the texture might be slightly drier in that tiny area.
How to Tell White Spots from Other Problems
It’s important to distinguish these common white spots from actual rot or disease. Here’s a quick comparison:
- White Spots (Moisture Bruise): Dry, chalky, firm to the touch. Skin is intact but discolored.
- Mold or Fungus: Fuzzy, can be white, green, or blue. Often smells musty. Discard.
- Soft Rot: The area is wet, slimy, and often smells foul. The potato will be mushy. Compost it.
- Sprouting: Eyes growing long shoots. The potato may be wrinkled. You can cut sprouts away and eat it if still firm.
When You Should Definitely Throw a Potato Away
While white spots are harmless, some conditions mean the potato is past its prime. Toss it if you see:
- Widespread green skin (which indicates solanine, a mild toxin).
- Deep wrinkles or severe shriveling (all-over dehydration).
- Large areas of soft, liquid decay.
- A pervasive foul or chemical odor.
The Main Causes of White Spots in Storage
Prevention starts with knowing the cause. These white spots are a direct result of storage conditions. The four key factors are humidity, temperature, air flow, and pressure.
1. Incorrect Humidity Levels
Potatoes need a high-humidity environment to prevent moisture loss. The ideal relative humidity for potato storage is between 90-95%. In a typical dry home, humidity can be as low as 30-40%, which quickly pulls moisture from the tubers.
2. Temperature Fluctuations
Temperature is critical. The perfect storage temperature is cool, around 45-50°F (7-10°C). Warmer temperatures encourage sprouting and dehydration, while temperatures below 40°F (4°C) can cause cold-induced sweetening. Frequent changes force the potato to “breathe” faster, losing moisture.
3. Improper Airflow and Pressure
Potatoes need to breath, but too much direct airflow will dry them out. Also, storing them in a deep pile where the bottom layers bear significant weight is a common culprit. The pressure bruises the lower potatoes, creating those white spots.
4. Exposure to Light
While light doesn’t directly cause white spots, it triggers greening and sprouting, which weakens the potato and makes it more susceptible to moisture loss and bruising. Always store in complete darkness.
Step-by-Step Guide to Perfect Potato Storage
Follow these steps from harvest to storage to minimize white spots and maximize shelf life.
Step 1: Cure Your Potatoes After Harvest
If you grow your own, never skip curing. This process heals minor wounds and toughens the skin.
- Gently brush off excess soil (do not wash).
- Place them in a single layer in a dark, well-ventilated area.
- Keep at 55-60°F (13-15°C) with high humidity for 10-14 days.
- After curing, the skins will be firm and dry to the touch.
Step 2: Choose the Right Storage Container
Avoid plastic bags and airtight containers. They trap moisture and promote rot. Instead, use:
- Burlap or paper bags: These allow for breathability.
- Cardboard boxes with ventilation holes.
- Wooden crates or baskets.
- You can line containers with newspaper to help buffer humidity.
Step 3: Prepare the Storage Location
Finding the right spot is half the battle. Ideal locations include:
- A root cellar (the traditional best option).
- A cool, dark basement corner.
- An unheated garage or shed (insulate if freezing is a risk).
- A dark cabinet in the coolest part of your home.
Avoid storing near heat sources like furnances, water heaters, or under the sink.
Step 4: Pack and Layer Correctly
How you place potatoes in there container matters greatly.
- Place a layer of dry straw, newspaper, or breathable fabric at the bottom of your container.
- Add a single layer of potatoes, ensuring they are not touching each other too much if possible.
- Separate layers with more newspaper or straw to cushion them and absorb excess moisture.
- Never stack potatoes more than 2 feet deep. Shallow containers are better than deep piles.
Step 5: Monitor and Maintain Conditions
Check on your stored potatoes every few weeks. Remove any that are sprouting, softening, or showing signs of rot immediately. One bad potato can spoil the bunch. If potatoes seem to be drying out, you can add a slightly damp cloth to the storage area to raise humidity, but ensure it doesn’t touch the potatoes directly.
Bonus Tips for Long-Term Storage
- Store Separately: Never store potatoes and onions together. Onions release gases and moisture that cause potatoes to spoil faster.
- Keep Away from Fruit: Apples, bananas, and other ripening fruit emit ethylene gas, which encourages potatoes to sprout.
- Don’t Wash Until Use: The dirt on homegrown potatoes actually provides a protective layer. Washing removes this and introduces moisture.
- Sort Regularly: Always use potatoes showing any damage or softness first, saving the perfect ones for later.
Frequently Asked Questions (FAQ)
Can I eat a potato that has a white spot inside?
Yes. If the white spot is dry and firm, it is simply a moisture bruise. Just cut it away and use the rest of the potato.
Are white spots on potatoes mold?
Typically, no. True mold is fuzzy and may be green, blue, or black. The common dry white spot is dehydration, not mold growth.
How do I prevent white spots on my stored potatoes?
Control humidity (aim for 90-95%), maintain a cool, stable temperature (45-50°F), store in breathable containers in the dark, and avoid piling them to deep to prevent pressure bruising.
Do white spots affect the taste?
Not significantly. The texture of the spot itself may be slightly drier or chalkier, but once removed, the rest of the potato tastes normal.
What is the difference between white spots and potato scab?
Potato scab is a soil-borne disease that causes rough, corky patches on the skin. It’s a surface issue and the potato is safe to eat after peeling. White spots from storage are often smoother and caused by internal moisture loss.
Why are my store-bought potatoes developing white spots?
Commercial potatoes are often stored in perfect conditions, but your home environment is different. The dry air in most houses, especially during winter, quickly pulls moisture from the tubers, leading to these spots.
Seeing white spots on your potatoes is simply a sign that they need a better storage setup. By focusing on humidity, temperature, and gentle handling, you can greatly reduce this common storage condition issue. Remember to cure homegrown harvests, choose breathable containers, and find that cool, dark, and slightly humid spot in your home. With these practices, you’ll be able to enjoy your potatoes at their best for much longer, minimizing waste and maximizing flavor from your garden or market.