Vegetables and mushrooms: seasonality, freshness, storage, safety, nutrition and cooking.
Small dry spots on an otherwise firm head are usually a quality problem you can trim. Dark areas that are wet, sunken, fuzzy, widespread, slimy, or bad-smelling are signs to toss the cauliflower.
Light yellowing is usually a freshness and quality change, not a safety problem by itself. Firm, dry cauliflower without mold or off odors can still be cooked; wet softness and decay change the answer.
A bitter eggplant is often simply overmature. Large seeds, spongy flesh, and dull skin support that explanation; discard it if bitterness comes with wet rot, slime, mold, or an off odor.
Dark seeds alone do not mean an eggplant has spoiled. They often show that the fruit is more mature, and cold storage can also brown seeds; judge the flesh for firmness, wet decay, mold, and off odors.
Cutting an onion ruptures cells that normally keep enzymes and sulfur-containing precursors separate. The reaction produces syn-propanethial-S-oxide, the onion’s lachrymatory factor, which reaches the eyes as vapor and stimulates sensory nerves, triggering tears.
Lettuce can turn brown for several reasons. Cutting and bruising stimulate phenolic metabolism that produces dark pigments, while ethylene from apples, pears, and other ripe fruit can trigger brown russet spotting. These physiological defects are different from bacterial rot or mold.
Among common vegetables, raw spinach provides about 2.7 mg iron per 100 g, beet greens about 2.6 mg, asparagus near 2.1 mg, and Swiss chard around 1.8 mg. These are total-iron numbers; vegetable iron is nonheme and is generally absorbed less efficiently than heme iron.
There is no universal winner. Cooking can reduce heat- and water-sensitive nutrients such as vitamin C and folate, while also breaking cell walls and increasing the availability of carotenoids such as lycopene in tomatoes and beta-carotene in carrots and spinach.
Broccoli yellowing usually signals senescence: chlorophyll breaks down as the florets age, especially with prolonged storage, warm temperatures, or ethylene exposure. UC Davis considers yellow florets the end of commercial shelf life, but yellow alone is not a safety diagnosis; mold, slime, rot, and off odors are different signals.
Fresh mushrooms deteriorate quickly. Slight drying, wrinkling, or darkening can simply mean age, while a slippery slime, sour or strong off odor, visible mold, and watery breakdown are clear reasons to discard them.
Pink or reddish ribs do not automatically mean lettuce is bad. UC Davis describes pink rib as a postharvest physiological disorder associated with overmaturity, long storage, or warmer-than-recommended conditions. If leaves remain reasonably crisp with no mold, slime, or off odor, the discoloration is usually a quality issue.
A cut onion can generally be kept about 7–10 days in the refrigerator when stored at 40°F (4°C) or below in a sealed container. That range is a storage guideline, not a guarantee: mold, slime, watery breakdown, or a clearly abnormal odor are reasons to discard it sooner.