Is It OK to Leave Butter Out?
Salted butter can safely sit at room temperature for 1-2 weeks in a covered butter dish. The salt and low moisture content inhibit bacterial growth. Unsalted butter should be refrigerated as it spoils faster. Keep butter away from light and heat, and use a butter dish with a lid to prevent oxidation.
Key Takeaways
- Butter is approximately 80% fat with very little water and protein - the components bacteria need to grow.
- Whipped butter and butter blends with oil should be refrigerated.
- If butter smells sour, cheesy, or looks darker yellow, it has gone rancid.
Explanation
Butter is approximately 80% fat with very little water and protein - the components bacteria need to grow. Salted butter has additional protection from salt, a natural preservative. At room temperature, salted butter stays soft and spreadable for up to two weeks.
The enemies of counter butter are light, heat, and air. Light and oxygen cause butter to oxidize and turn rancid, developing off flavors. A covered butter dish or butter crock protects against these. A French butter keeper (butter bell) uses water to create an airtight seal.
Unsalted butter lacks the preservative effect of salt and should be kept refrigerated, with small amounts brought to room temperature for spreading as needed. In hot climates or summer months, even salted butter may need refrigeration to prevent melting and faster spoilage.
The FDA considers butter safe at room temperature for short periods, and European countries routinely store butter on the counter. In France and Ireland, room-temperature butter is standard kitchen practice. The key threshold is ambient temperature: below 72°F (22°C), salted butter remains stable. Above 77°F (25°C), bacterial growth accelerates and the butter softens to the point of melting.
Only keep out what you will use within a day or two if you go through butter slowly. A full stick left out for two weeks in a warm kitchen will taste noticeably different from fresh. The best approach for infrequent butter users is to slice off a tablespoon or two and leave that amount in a small covered dish while the rest stays refrigerated at 35-38°F.
Things to Know
- Whipped butter and butter blends with oil should be refrigerated.
- If butter smells sour, cheesy, or looks darker yellow, it has gone rancid.
- Clarified butter (ghee) has even longer shelf life at room temperature because milk solids are removed.
- Butter with herb or garlic additions should always be refrigerated since the added ingredients introduce moisture and potential bacteria.