Yes, butter should generally be refrigerated for long-term freshness, but salted butter can be kept on the counter for a few days to a week in a covered dish, while unsalted, whipped, or cultured butter should always be refrigerated, as it spoils faster without salt. The fridge keeps it fresh longer (months), while room temp is for quick use, protecting from heat, light, and air in a covered container to slow spoilage.
Unsalted, whipped or raw, unpasteurized butter is best kept in the fridge to minimize the chances of bacterial growth (4). Salted butter does not need to be stored in the fridge since the risk of bacterial growth is so low.
In Europe, people often keep butter at room temperature. This keeps it soft and easy to spread. European butter has a rich flavor because of its higher fat content and traditional methods.
(As a fellow food writer often says to me, “It's food—do whatever you want with it!”) Your mileage may vary, but the US Department of Agriculture recommends that you leave butter unrefrigerated for no more than two days, after which its fat content can turn rancid and take on unpleasant flavors.
Butter can absolutely be kept out on the counter, but only under the right conditions. If you're storing salted butter, a couple of days at room temperature is usually safe. Unsalted butter is best left out only briefly, and garlic herb butter should always be refrigerated after two hours.
Not enough to promote significant bacteria growth. This is especially the case with salted butter, since salt inhibits the growth of bacteria. Salted butter will keep for weeks at room temperature.
How long can butter sit out? Butter, like all food products, will spoil eventually. There is still a debate as to how long butter can sit on the counter before going bad. For best quality, keep butter in a covered dish and use it within two days.
Since butter is mostly fat, it creates a barrier that makes it almost impenetrable to bacteria. Another factor determining how long butter is safe to be left on the counter is the presence of salt. Salt acts as a preservative because it reduces the activity of water in food.
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).
Salted butter is less prone to going bad on the counter than unsalted butter. If you're a serious supporter of leaving butter out, go with the salted kind. It's important to note, however, that the amount of salt in different brands of butter can vary.
Many Italians use UHT (ultra-high temperature) processed milk, which is heated to a high temperature to kill bacteria and can be stored without refrigeration until opened.
The higher fat content results in a richer flavor and a softer texture, which is particularly great in pastries, and even things like cookies and cakes! With less water content and higher fat, French butter is more pliable while it's cold making it easier to work into crusts for better results.
Italian eggs are gently wiped clean from debris before they're packaged and ready for sale, but never washed. Because they have this protective outer layer they don't need to be refrigerated and can stay at room temperature for a week or two without any deleterious effect.
Everyone knows you need to keep dairy products like milk and cheese stored in the refrigerator, or they'll spoil. Butter, on the other hand, is a little different. Some people keep it in the fridge, but others store it on the counter so it's always ready to spread across toast or a crusty piece of bread.
If you buy butter far in advance of use, store butter in the freezer. This is the best way, as freezing butter does not alter the taste or texture of butter. If you use butter frequently, keep it in the refrigerator away from aromatic foods (such as garlic or onions) because butter absorbs odors easily.
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.
If your butter tastes sour, chances are it's definitely past its sell-by date. “Rancidity has nothing to do with microbes or safety,” Chapman says. “What's happening is oxygen is binding to the fat and changing the chemical components, which can lead to a terrible taste, but it won't make you sick.”
A better indicator of true expiration is the appearance, smell, and taste of butter. Spoiled butter can smell (or taste) sour or tangy, and can change in color and texture.
As time went along, earthenware containers, which allowed evaporation of moisture, thus facilitating, cooling, became popular for both the storage of water and butter. Earthenware maintained its popularity until refrigeration came along in the mid-20th century.
Best to keep it at room temp. I keep my butter out once I remove the wrapper. I would leave it at room temp unless you rarely use butter. It stays safe for quite a while and if it is not good anymore, you will know immediately because it smells wrong.
While it may be tempting to scrape off the offensive fuzz and eat the food anyway, that might not be the best course of action. There's no way of knowing by sight whether a mould is safe or harmful. Some moulds can actually be very, very toxic to human beings.
Fresh butter smells clean and slightly sweet. If it starts to smell sour, metallic, or like the inside of your refrigerator, there's a good chance it's spoiled." In general, we recommend that if your butter doesn't smell right, it's best to avoid it.