Fresh butter is usually a light yellow color, but as it begins to spoil, it may turn a darker shade of yellow or even beige. Venae Watts, a butter maker at Minerva Dairy, told Reader's Digest that spoiled butter will also show mold or other colored spots.
Any sour or off-putting smell means it's a goner. Same goes for taste: If it tastes sour or off, toss it out. 5 And don't worry, a small taste of rancid butter won't hurt you. Of course any visible mold, discoloration, and changes in texture are visible cues that it's time to throw the butter in the trash.
Q: When I cut through some blocks of butter there is a darker yellow layer around the outside. Is the butter still OK to use in my baking? A: If you also take a whiff you may also notice it has a slightly sour smell. Both this and the darker yellow layer are both signs that the butter has started to go rancid.
Discoloration is a sign of rancid butter. Good butter has an even yellow color from inside out. Slice a small portion of your butter, if the inside looks brighter or lighter, then it has gone bad. Black spots on butter are signs of mold formation.
A little brown butter is a good thing, but too hot and the solids will start to blacken and then you'll be in trouble. They'll be bitter, the pan will smoke, and your pancakes will take on the blackened solids. No good.
Browning butter is one example of the Maillard reaction. As butter heats up, the water in the butter evaporates and sugars and amino acids in the butter react to create new flavor compounds and turn from white to brown.
Since butter contains quite a lot of fat, it's prone to oxidation. I'm sure you've seen butter with its surface oxidized before. Any time you cut a slice of butter and the inside is brighter than the outside, it's the result of oxidation.
It should be pointed out that rancid butter can't make you sick, but it won't taste or smell very good. Rancidity is caused by exposure to oxygen, light and heat. So, to prevent rancidity, keep your butter in an opaque butter dish with a lid.
When milk or cream is churned, as is required when making butter, the membrane is broken and beta-carotene is released, turning the butter solid yellow. Interestingly, other animals don't store beta-carotene in the same way that cows do, so butter made from sheep's milk or goat's milk is white.
Essentially, a natural grass-fed diet will result in a yellow coloured butter while cows that are fed mostly grains will produce a lighter coloured butter.
Butter has a natural pale-yellow color but can range from deep yellow to white depending on feed used and the breed of cow the milk originates from.
Left unwrapped, either salted or unsalted butter will keep in the refrigerator for at least 8 weeks. Salted butter, in fact, will last an additional 4 weeks, since salt acts as a preservative. Once you open the wrap, however, butter should be used with in 3 weeks.
Unless you can see any visible signs of expiration or notice a sour, unpleasant smell, it's generally safe to use expired butter.
Butter is perfectly safe to eat even after the expiration date has passed, so long as it still looks and tastes normal. Butter can last a longer period of time than, say, yogurt, milk, or sour cream because butter is made up mostly of fat, which makes it hard for harmful bacteria to form on the surface.
The U.S. Department of Agriculture recommends leaving butter at room temperature no more than two days. After that period of time, the butter can turn rancid. This will cause off flavors and unpleasant texture. However, if you follow the butter storage tips above, butter can stay fresh up to two weeks on the counter.
You can keep it in the fridge for 10 days or two weeks if the box of butter is open. Also, make sure you store it in an airtight container. If the box is unopened, you can store it for up to a month.
If your butter smells or tastes sour or rancid, it's time to toss it.
The science behind this is the beta-carotene (yellow pigment) found in the grass eaten by cows; which is stored in the cows' fat and carried into the milk. Because the milk is mostly water the yellow color doesn't come through with the milk and instead is carried with the fat which produces the butter.
Butter that has begun to go rancid and develop mold will become discolored. Butter typically has an even yellowish color. When butter develops mold, it will become discolored. You will likely be able to see mold starting to grow in it.
You can tell your browned butter is burnt by using a light colored stainless steel pan to monitor the changing color of the milk solids in the butter. If the color of the solids change from dark brown to black you've gone too far. You will also notice a loss of nutty aroma.
You might think the blackened butter is definitely burnt and is a toss away, actually that is not so. It has a very intense nutty smell, but still sweet, not bitter-burnt, and can still be used for baking. You can strain out the burnt milk solid to save it.
Brown butter has a deep golden brown, caramely color. As soon as you begin to see this color in your butter, remove it from the heat because it'll continue to brown a bit. Burnt butter will be darker and begin to have a burnt smell.
What are those brown specks in the butter? Those brown specks are actually toasted milk solids. But, for all intents and purposes, they might as well be gold! They have so much flavor, so do not throw them away!
You will be surprised to know that even if you store butter at room temperature, it's safe to consume it a week after the expiry date. You can even consume it after a month of its expiry date, but for that you have to store it correctly.