Is It Safe To Put Softened Butter Back In The Refrigerator?

You're getting ready to bake cookies, so you pull the butter out of the fridge an hour ahead of time to soften it. Life happens, pushing your schedule back another thirty minutes. When you finally get around to making your dough, however, you realize that you've softened too much butter. By then, the extra amount will have been left unrefrigerated for more than two hours. Is it safe to pop it back in the fridge? The answer is a resounding yes.

Butter is typically softened at around room temperature, and according to the U.S. Department of Health and Human Services' (HHS) Foodkeeper app, it can keep at room temperature for up to two days. While different agencies have different specifications for what exactly room temperature is, they all tend to fall within the range of 68 to 77 degrees Fahrenheit. If you live somewhere where the average daily temperature is higher than that, it might be best to put that softened butter back in the refrigerator as soon as you can.

If you want to avoid keeping butter out for too long, you could try some of the faster ways of softening butter instead, like cubing it and putting it inside a warm — but not running — microwave for a few minutes. The most fun way to soften butter fast is to put it in a plastic bag and give it a few whacks with a rolling pin. (Might as well get a quick workout in before making those cookies.)

A 2014 study published in the Korean journal Food Science of Animal Resources suggests unrefrigerated butter could stay edible for much longer than the two days recommended by HHS. Researchers inoculated butter samples with listeria and E. coli, and found that both refrigerated and room temperature samples didn't show any bacterial growth. In fact, the amount of bacteria decreased by a small degree, suggesting butter doesn't support any growth at all. What did change, however, was the sensory qualities and acidity of the butter, with both measures scoring lower at higher storage temperatures.

Based on these findings, researchers determined that butter stored at 77 degrees Fahrenheit had a shelf life of 6.1 months. Shelf life was even longer at colder temperatures, reaching 17.18 months at 59 degrees and nearly 22 months at 50 degrees. It should be noted, however, that the experiment was done under highly controlled conditions; the butter casually sitting on your counter might still be at risk for contamination.

This is why those viral French butter bells from a few years ago may help keep butter safe and spreadable at room temperature. They create an airtight seal around the butter that prevents contaminants from getting in, while also blocking out odors that can make your butter taste strange. That said, it's still safest to refrigerate butter — you don't know how long it's actually been in storage before you bought it, or at what temperatures.