Lemons

Lemons keep about a week on the counter and 3–4 weeks refrigerated. For longevity the fridge wins clearly.

The technique that works best: store them in a sealed bag or container of water in the refrigerator, which keeps them plump and juicy for a month or more. Otherwise, loose in the crisper is fine — better than a sealed dry bag, which traps humidity against the peel and encourages mold.

Cut lemons should be wrapped tightly, cut-side against plastic, and used within a few days.

Zest before you juice. Lemon zest freezes indefinitely and a spent lemon half cannot be zested.

Juice freezes perfectly in ice cube trays, and frozen lemon juice is far better than the bottled product.

Lemons are among the most acidic foods in a kitchen, at a pH of about 2.0–2.6. That is well below the threshold at which foodborne bacteria can grow, which is why lemon juice is used as a preservative and why lemons themselves are so stable.

Their limiting factor is therefore dehydration and mold rather than bacterial spoilage. The peel is a good moisture barrier but not a perfect one, and a lemon left on a warm counter steadily loses water — becoming light, hard, and disappointingly dry inside while still looking acceptable. Weight is a better guide than appearance: a good lemon feels heavy for its size.

Mold, when it appears, is usually Penicillium, blue-green and fuzzy, starting at the stem end or a bruise. As with all high-moisture fruit, a moldy lemon should be discarded whole.

Lemons are non-climacteric and do not ripen after picking, so there is nothing to gain by leaving them out.

One thing worth knowing: most commercial citrus is coated with a food-grade wax to replace the natural wax lost in washing and to slow moisture loss. It is safe, but if you are using the zest, scrub the fruit under warm water first.