Beef kidney has a strong, unpleasant smell that can be off-putting. But why does it smell so bad? There are a few reasons that contribute to the foul odor of beef kidney.
The Concentration of Waste Products
One of the main reasons beef kidney smells so terrible is that kidneys filter waste from the blood. They contain high concentrations of urea and uric acid, which are waste products excreted from the body. When kidneys are cooked, these waste products break down, releasing ammonia and causing a strong urine-like odor.
The job of the kidneys is to filter the blood and remove toxins, excess minerals, and other impurities. All of this waste collects in the kidneys before being excreted through urine. So while the kidneys play an important role in the body, they also end up containing a high concentration of smelly metabolic waste products. No wonder they make such a stink when cooked!
Odor Causing Compounds in Beef Kidney
In addition to urea and uric acid beef kidneys contain other odor-causing compounds
- Creatinine – a chemical waste product of creatine metabolism in muscles
- Sulphur-containing amino acids like cysteine and methionine – these contain sulphur which gives a foul, rotten egg-like smell when cooked
- Indoxyl sulfate – a metabolite of tryptophan breakdown that gives an unpleasant faecal odor
Some of the volatile organic compounds found in cooked beef kidneys have been identified as:
- Ammonia
- Hydrogen sulphide
- Methyl mercaptan – commonly associated with the smell of faeces
- Dimethyl sulphide – associated with cabbage-like smell
When all these smelly compounds are released during cooking, it creates an overpowering stench that many find nauseating The high concentrations of waste products in the kidneys are the main source of the objectionable odors
Blood and Fat Content
Beef kidneys are very high in blood content This gives them a distinct bloody, metallic smell. They are also moderately high in fat When the fat renders during cooking, it produces a greasy smell. The combination of the bloody and fatty odor contributes to the overall strong smell.
Cooking Method
How beef kidneys are cooked also affects their smell. Dry heat cooking methods like grilling, frying or roasting tend to produce stronger odors than moist heat methods like stewing or boiling. This is because the proteins and other compounds degrade more rapidly at higher temperatures, quickly releasing stinky volatile compounds.
Slow cooking methods like stewing for a long time can help reduce the odor by breaking down some of the harsher volatile compounds. However, the smell can never be fully eliminated given the kidney’s high waste content.
Storage and Freshness
Like any meat, how fresh the kidneys are and how they are stored affects the smell. Kidneys are very perishable organs, so they spoil rapidly if not stored properly. If the kidneys have been sitting around in warm temperatures or stored in plastic packaging that causes condensation, bacteria growth and spoilage happen quicker, creating extremely foul odors.
Kidneys need to be very fresh, ideally used within a couple days of slaughter. Freezing can help prolong their freshness. Thoroughly rinsing and soaking kidneys in cold water, milk, or vinegar solutions may also help reduce some residual odors. But at the end of the day, the fundamental composition of the kidneys leads to a persistent foul smell when cooked.
Tips to Reduce the Odor of Cooked Kidneys
Here are some tips that may help decrease the stench of cooked kidneys:
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Purchase kidneys as fresh as possible, within 2 days of slaughter. Avoid old, slimy looking kidneys.
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Store kidneys well wrapped in freezer bags in the coldest part of the freezer, use within 2-3 months.
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Rinse kidneys well under cold running water before cooking. Soak in milk or vinegar solution for 30 mins.
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Simmer kidneys in milk, broth or water rather than dry roasting or grilling them.
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Add spices and acidic ingredients like vinegar, tomato, lemon juice to cooking liquid.
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Cook kidneys partially submerged in liquid rather than openly exposed.
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Cook outdoors or under a vent hood to allow smells to disperse. Use exhaust fans.
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Cook kidneys just before serving rather than letting them sit. The smell dissipates faster when hot.
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Soak cookware in baking soda solution after cooking kidneys to remove clinging odors.
Why Some People Are More Sensitive to the Smell
While most people find the smell of cooked kidneys offensive, some seem to be much more sensitive than others. There are a few reasons for this:
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Genetic differences in odor receptors – Some people have more odor receptors or receptors that are more sensitive to certain compounds. This makes them better smellers.
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Damage to olfactory senses – Injury, aging, viruses, sinus issues can damage smell receptors, making some people less sensitive.
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Exposure – People used to the smell of organ meats and who eat them more regularly can become desensitized. Less exposure can mean more sensitivity.
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Associations – If the smell triggers memories of foul odors, reminds them of urine/faeces, or if they’ve become sick from the smell before, people can develop strong aversions.
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Disgust response – Some have an inherent heightened disgust response to the meat and odor that causes them to have a more intense reaction.
So genetics, olfactory damage, lack of exposure, and psychological/instinctual factors can all play a role in why some people seem to find the smell especially revolting and intolerable.
Coping With the Odor of Cooked Kidneys
If you find the odor of cooked kidneys particularly disgusting and intolerable, then it’s best to avoid cooking them. With a very sensitive nose and strong aversion to the smell, cooking kidneys is likely to always be an unpleasant experience. You can still obtain the nutritional benefits by having someone else prepare them for you. Here are some other tips:
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Wear a nose clip when handling raw kidneys to block the smell.
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Cook kidneys when you can ventilate the kitchen well, turn on fans and open windows.
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Use odor eliminating candles, sprays or diffusers during and after cooking.
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Cook a small amount well diluted in liquid until you become desensitized.
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Hold your breath when checking on cooking kidneys, breathe through mouth.
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Have someone else handle the prepping and cooking completely if smell is too intolerable.
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Explore taking kidneys in capsule form or grinding into supplement powder to avoid smell.
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Switch to less odorous organ meats like liver, heart or pancreas instead.
Some people have no choice but to tolerate the bad smell and cook kidneys for their pets’ food or for cultural reasons. For those with an extreme aversion, the best solution may be avoiding direct contact and having support. With time, the nose can adapt, but the odor can be challenging especially at first. Finding ways to manage exposure can make cooking the smelly kidneys more bearable.
The Bottom Line
Beef kidney has an exceptionally strong, urine-like smell when cooked due to its high concentration of metabolic waste products and odor causing compounds. How fresh the kidneys are and how they are cooked also affects the smell. For those highly sensitive to the odor, it can be extremely nauseating and intolerable. However, there are ways to reduce the odor and cope with cooking kidneys if you are determined to eat them for their nutritional content. Being aware of the reasons kidneys smell so ghastly can help those offended by the odor understand where that distinctive stench comes from. Holding your nose and getting used to the stink may be necessary if kidneys are going to be a part of your diet.