Is It Safe To Eat 2-Year-Old Frozen Butter?

You're scrambling around your kitchen hoping to whip up a comforting batch of cookies, but the recipe calls for butter. Determined, you search the bowels of your refrigerator for a stray bar or tub of something leftover from the last time you baked. But wait — did you freeze a stick sometime last year? Sure enough, there's frozen butter waiting for use, but the expiration date is long past: Two years, in fact. You're desperate, however, and can't be bothered to run to the store or order instant delivery. 

According to the American Butter Institute, butter is around 80% butterfat and made with water and milk proteins. Cultures and natural flavorings are often added to the dairy product to help preserve creamy freshness (via Cooks Illustrated). Yet butter expires, and it's usually easy to tell when a bar is rancid: Mold, discolorations, or an "off" smell present (per Spoon University). So how long does frozen butter stay fresh?

As with most frozen food items, the length of freshness depends on how you store the product. Foods Guy recommends wrapping your butter in foil and covering it with plastic wrap or placing the foiled mass into an airtight container or bag. Research has supported this suggestion, with a study published in the Journal of Agricultural and Food Chemistry proving that wrapping butter in foil (not parchment paper) minimizes the aging process and helps keep butter usable for a longer time frame.

When stored properly, butter frozen in bulk can last up to 18 months, according to a study published in the Journal of Dairy Science. Individual sticks, however, begin to decrease in quality around the year mark (via Still Tasty). Depending on how you store your butter and what kind of butter it is, chances are high that any two-year-old batch has aged, and not in the way you'd like. Opt for a cooking substitute or save your baking for another day.