How to Store Potatoes and Onions (And Why They Hate Each Other)
They are the foundation of hearty cooking, but storing them together is a recipe for rapid spoilage. Learn the rules of the dark pantry.
The Classic Pantry Mistake
Potatoes and onions are often sold near each other in the grocery store, and they are cooked together in countless stews, hashes, and roasts. Because they are both robust root vegetables, it seems entirely logical to store them together in the same basket at the bottom of the pantry.
This is a massive storage error. If you store potatoes and onions in close proximity, you will find that your potatoes rapidly sprout long, alien-like green tendrils, and your onions turn to mush in a matter of weeks.
The Chemical Warfare
While they pair beautifully in a hot skillet, they are bitter enemies in storage.
- Onions naturally emit high levels of ethylene gas (the same ripening hormone produced by bananas and apples).
- Potatoes are incredibly sensitive to ethylene gas. When exposed to it, the potato believes it is time to reproduce. It rapidly breaks down its starches into sugars to fuel the growth of sprouts (the "eyes").
- Conversely, potatoes naturally emit moisture. Onions require a completely dry environment to prevent rot. The moisture from the potatoes will cause the papery skin of the onions to become damp, leading to rapid mold and spoilage.
How to Store Potatoes Properly
Potatoes are living organisms that want to grow into new potato plants.
- The Three Rules: They require complete darkness, cool temperatures (but not freezing), and moderate ventilation.
- The Refrigerator Danger: Never put raw potatoes in the fridge. The cold temperatures trigger an enzyme that rapidly converts the potato's starches into sugar. The potato will taste unpleasantly sweet and will burn instantly when fried due to the high sugar content.
- The Solanine Warning: If potatoes are exposed to sunlight, they will turn green. This green color indicates the presence of solanine, a bitter and mildly toxic compound. Store them in a dark cabinet, a paper bag, or a cardboard box in a cool pantry or basement.
How to Store Onions Properly
Onions simply want to stay dry.
- They require excellent air circulation and low humidity. The mesh bags they are often sold in are ideal.
- Keep them in a cool, dark pantry, completely separated from your potatoes (preferably on opposite sides of the kitchen).
- Do not put whole, uncut onions in the fridge, as the humidity will make them soft and moldy.
By giving these two kitchen workhorses their own separate, dark, dry territories, you can extend their shelf life for months.