How to choose foods, interpret labels and quality signals, judge ripeness and understand origin or commercial categories.
Black or gray spots on tempeh are often normal Rhizopus spores from fermentation; unusual colors, slime, mushiness, or a strongly unpleasant odor point to a different problem.
A thin layer of oil or watery liquid can separate from hummus during storage and may be stirred back in, but refrigeration history, mold, gas, slime, and off odor matter more than separation alone.
Oil separation is normal in many natural peanut butters because they lack strong stabilizers; stir it back in unless the spread shows rancid odor, mold, contamination, or package damage.
Soft cereal often reflects absorbed humidity and a loss of quality; mold, rancid odor, wet clumps, stains, or insects indicate spoilage or infestation.
Salt usually cakes because it absorbs humidity and can still be used; dirt, insects, mold on contamination, or unusual odor are different problems.
Stale-oil, cardboard, paint, soapy, or old-nut odors can signal rancidity in oats; cooking does not reverse oxidation once the fats have deteriorated.
Milky or cloudy albumen usually points to a very fresh egg; pink or green colors, off odor, or poor storage call for a different assessment.
A yolk that breaks easily often reflects a weaker membrane from age or a shell-edge puncture; by itself, it does not prove the egg is spoiled.
A sulfur smell can be normal in an overcooked hard-boiled egg; putrid odor, slime, mold, or poor refrigeration point to a different problem.
Smooth white specks are often chalazae or dense albumen, normal egg structures. Unusual colors, fuzz, or bad odor call for a different assessment.
Dark yellow or translucent edges often come from oxidation, drying, or temperature changes; rancid odor, mold, or unusual stickiness are stronger reasons to discard butter.
Paint-like, cardboard, soapy, or stale-fat odors usually point to oxidative rancidity. Clearly rancid butter should be discarded even when no mold is visible.