The white stuff on your butter is usually harmless milk solids (proteins and water) that separate during melting, but if it's fuzzy or discolored, it's likely mold, which means you should discard the butter, as mold can have deep roots and produce toxins. Normal white specks are fine, especially after melting or partial thawing, but fuzzy spots indicate spoilage.
At the bottom there is a thick white layer. That's whey, or more correctly, it's the remains of the buttermilk. It's mostly water mixed with proteins, it is this part that makes the butter splatter and burn.
Spoiled butter can smell (or taste) sour or tangy, and can change in color and texture. Mold or colored spots are a clear indication that butter has gone bad, but even a subtle shift from pale yellow to dark is a sign that it's time to throw it out.
Molds are fungi, some of which can trigger allergies and cause breathing problems. Certain molds can release harmful toxins (many of these don't affect butter, though). And although accidentally eating a little mold is unlikely to cause serious harm, it's safest to throw out moldy butter.
Butter molds had fancy designs carved into the press so that the impression was left on top of the butter. Common designs were a sheaf of wheat, pineapple, thistle, cow, rooster and geometric designs. Butter would have been filled into the mold and then the plunger pressed to form a tight shape of butter.
Nope toss it. The mold spore will be inoculated through out the butter. Once mold shows up it is too late in stuff full of moisture. You can only cut mold off cheese if the cheese is aged or dry.
Efflorescence, a crystalline growth, has a white, almost fluffy appearance and is often mistaken for white mold. It typically grows on brick, concrete, and stucco and is caused by salt deposits. Efflorescence does not pose the same health threats as mold.
An easy way to tell if your butter has started to go bad is by looking at it. Butter going rancid will change color from off-white to yellow and brown. It will also have a change in texture. If you see mold, you should immediately throw it out.
Most people will be just fine but watch for any symptoms. “Having shortness of breath or trouble breathing, nausea, vomiting and diarrhea within a day or so of eating moldy food could be a sign of food poisoning or an allergic reaction,” Spina said.
To simplify, the straight answer: Yes, heat can kill mold spores, but cooking moldy food doesn't make it safe to eat.
TRUST YOUR SENSES: LOOK, SMELL, AND TASTE BEFORE YOU WASTE
Look at it: if you notice any mold or discoloration, it's best to throw it out. Next, smell it. Fresh butter has a mild, creamy scent. If it smells sour or rancid, it's time to discard it.
Unsalted butter can last up to three months in the fridge. (If the butter is unwrapped, shorten those projections to about two months in the fridge.) And in a cabinet or on the counter, you can leave butter out for a few days to a week without it spoiling.
If you're unsure if your butter is OK to eat, simply give it a smell. If it's rancid it will most definitely smell off, and if you're willing to give it a taste, it should taste unpleasantly sour. At that point it's time to reach for fresh butter. Another factor to consider is whether or not its salted.
Natural butter can range from creamy white to pale yellow to saffron yellow. Color differences in milk and butter are primarily due to the breed of cattle producing the milk. Some breeds produce white butter; others, yellow. The most popular breed of dairy cow in the United States, the Holstein, produces white butter.
Smell: If butter smells sour, cheesy, or otherwise off, discard. Taste: If you notice a sour, bitter, or off flavor, discard. If the butter simply absorbed flavors from nearby garlic or onions in the refrigerator, it's still safe to use in cooking (although you might want to avoid using it for baking applications).
Although the butter is not a highly perishable food, it does undergo spoilage by bacteria and molds. The main source of microorganisms of butter is cream, whether sweet or sour, raw or pasteurized1. Yeast and molds are important spoilage microorganisms of butter and can result in surface discoloration and off-flavor.
If it's covered in mold, toss out the entire food.
What are symptoms and effects of mold exposure?
The butter industry has constantly faced the possi- bility that mold might appear on butter, wrappe'rs, or packages before the butter reached the consumer. The molding of butter is by no means a new problem, nor is there any reason to believe that it is more common today than it was fifty years ago.
The solid, white stuff is the milk proteins. The sizzle of the heated butter was the water boiling away. The foam which forms on top of the butter is mostly due to air that is trapped in the butter during processing.
Eating rancid butter is unlikely to lead to serious illness, but it might cause an upset stomach or mild digestive issues, such as nausea. If you suspect butter is spoiled, it's best to err on the side of caution and toss it.
Is White Mold Dangerous? Make no mistake, white mold has its health risks, but it's just as dangerous as any other color of mold. Continued exposure to any kind of mold can pose a serious threat to your health with symptoms including headaches, nausea, dizziness, allergies, and respiratory infections.
The easiest way to differentiate between the two is via a water test. Spray a small quantity of water on the suspected substance. Efflorescence will quickly dissolve, while mold growth will remain. The mold growth will likely mat down a bit, so look carefully for lingering material.
What Does White Mold Look Like? White mold typically appears as a fuzzy or powdery texture. It can look fluffy and sometimes produces a light, feathery layer over an area. It is usually white early in its growth, but it can develop into gray, black, or green shades over time.
The average person likely won't get sick from ingesting small amounts of mold, the experts note. However, eating larger quantities of mold may result in nausea or stomach upset. Chances are you won't be able to eat very much mold because humans have a natural aversion to spoiled foods, Wee notes.