How Long Can Yogurt Sit Out?
It's a critical component of the morning rush routine: packing lunch. And if the mid-day meal (or late-morning snack) consists of yogurt, you typically want to fortify that little cup with ice packs. But inevitably, they get lost at school, left behind at work, or just go MIA in general. So when that happens, can you safely bring yogurt with you and consume it later, despite the lack of refrigeration? If you eat it within two hours, then yes.
According to the U.S. Department of Agriculture (USDA), any perishable items, like sandwiches layered with deli meat and cheese, or yogurt, will remain safe for up to two hours at room temperature. The window shrinks to one hour when the temperature is 90 degrees Fahrenheit or higher. Any longer and the risk of bacteria growth climbs significantly. The farmer-founded nonprofit U.S. Dairy adds that microorganisms tend to form more easily in yogurt with added fruit or sugar (which seems to be the majority of yogurts on the market these days). That means you should also consider how many errands you need to run on grocery shopping day — you don't want your dairy supply to spoil in the trunk before making it home.
Pack it up
The USDA recommends always packing a minimum of "two cold sources" with perishable food when you need to take it to go — think re-freezable hard plastic ice blocks or soft gel packs. Also, it's far past time to kick the brown bag habit. Insulated boxes or thermal sacks are better at ensuring your lunch stays at a safe temperature (40 degrees or below) until it's break time. If those aren't handy, you could freeze a single-serve container of yogurt overnight and rely on it to thaw by lunch — just keep in mind that the consistency might be somewhat off.
There are several key signs that it's time to chuck your yogurt because of spoilage. The most obvious might be evidence of mold growth, which would produce coloring you wouldn't expect to see in the cup, like green, gray, or blue. A very thin, clear film at the top is harmless (that's the whey), but if it's more like an opaque pool, that's another indication yogurt has gone bad. Finally, any dairy product with a rancid aroma should immediately be off-putting and prompt a trip to the trash can. Keep those signals in mind when it comes to eating yogurt past its stamped sell-by date, which is generally safe if the package hasn't been opened. Once the seal has been broken, the clock starts ticking, however. You've got about one to two weeks.