Broccoli

Broccoli keeps 3–5 days refrigerated, and it wants cold, moisture, and airflow all at once.

Store it in the crisper in a perforated or loosely open bag. Broccoli respires vigorously and needs oxygen; sealed airtight it suffocates and develops strong sulfurous odors.

The method that works best is to treat it like a bouquet: stand the stalk in an inch of water in a container, cover the head loosely with a bag, and refrigerate. It stays firm noticeably longer.

Do not wash it until you use it. Moisture trapped in the dense florets is exactly where rot starts.

Keep it away from apples and other ethylene producers — broccoli is highly ethylene-sensitive and yellows quickly near them.

Broccoli freezes well once blanched, for about 12 months. Unblanched it develops off flavors.

Broccoli is an immature flower head, harvested before the buds open, and it is doing its best to keep developing after you buy it. That is why it fails faster than a root or a bulb — it is metabolically active tissue in the middle of a project.

The yellowing you see is the buds beginning to open and the chlorophyll degrading. It is accelerated dramatically by ethylene and by warmth. Yellow broccoli is safe but bitter and past its best; open yellow flowers mean it has bolted well beyond usefulness.

Broccoli's smell tells you a great deal. It is a brassica, rich in sulfur-containing glucosinolates. As the tissue breaks down, enzymes convert these into sulfur compounds — the same family responsible for the smell of cooked cabbage. A faint sulfurous note in aging broccoli is normal chemistry; a strong, sharp, rotten-egg smell means it should go.

Because the head is dense and the florets trap moisture, soft rot takes hold readily: bacteria producing pectin-degrading enzymes turn the florets slimy and brown-black.

Discard on sliminess, blackened or mushy florets, or a strong sulfurous smell. Slight yellowing alone is a quality matter and the broccoli is still edible.