How to Tell If Liver and Kidney (Offal) Have Spoiled

The quickest way to tell if offal such as liver and kidney has spoiled is a smell test: fresh liver has a mild iron-like smell, while spoiled liver has a sour or sharp, almost ammonia-like odor. This ammonia smell is more pronounced in kidneys because kidney tissue naturally contains urea, and the odor increases quickly when spoilage begins.

What should fresh liver and kidney look and feel like?
Fresh liver is dark red to burgundy, with a shiny, moist surface that is not sticky, and a mild metallic, iron-like smell. Fresh kidney is light reddish-brown and feels firm and elastic to the touch. In both, loss of surface shine, dark spots, or discoloration is an early sign of declining freshness; at this stage, there may not yet be a noticeable odor, but the texture may have started to change.

What are the signs of spoilage?
Spoiled liver turns gray or greenish, develops a sticky, slippery texture, and has a sour or sharp, almost ammonia-like smell. In kidney, spoilage is first noticeable in the smell: a mild ammonia odor is natural for kidney, but if it becomes sharp and strong enough to make your eyes water, the kidney should no longer be eaten. In both types of offal, a slippery film that transfers to your finger when touched may indicate that spoilage has begun even before it is visibly apparent.

Why does offal spoil faster than other meats, and how should it be stored?
Offal contains more enzymes and moisture than muscle meat, making it more favorable for bacterial growth. While red meat lasts 3–5 days in the refrigerator, liver and kidney should generally be consumed within 1–2 days. If they will not be used right away, freezing offal delays spoilage for 3–4 months. It is also important to check whether offal has been kept in a cold chain when buying it; liver left on a counter for a long time may already have begun to spoil before it reaches home.

Is there a difference between lamb and beef offal?
Lamb liver and kidney are generally more delicate in texture than beef offal and may begin to spoil sooner; for this reason, cooking lamb offal on the day of purchase is more critical than for beef offal. Beef liver has a somewhat denser texture, so signs of spoilage may appear about 1 day later. Kidney spoils faster than liver in both animals; therefore, if you buy both and will not cook them on the same day, consuming or freezing the kidney first is the safer order. When buying offal, also pay attention to the amount of bloody liquid collected under the package or display; more liquid than usual may indicate the product has been held longer than expected. The safest approach is to cook offal from a butcher the same day or, at the latest, the next day. Briefly soaking liver and kidney in cold water and changing the water before cooking reduces the slight blood odor that can be present even when fresh; this is an optional preparation step for a natural odor that is not a sign of spoilage, and it does not salvage spoiled offal. Pour out the soaking water without splashing, then wash the sink and surrounding surfaces with hot, soapy water and sanitize them. This small preparation step can also improve the overall flavor of the cooked offal.