How Long Can You Leave Milk Out of the Fridge?

It’s a busy morning – getting ready, eating breakfast, fixing lunch, checking email, grabbing homework. Then you notice something out of place. A carton of milk is sitting on the counter.

We’ve probably all had this happen and, at that point, three questions run through our minds: How long has the milk been out? Is it still safe? And who left it out?

Our very own registered dietitian Sarah Downs stepped in to help us find some answers.

Okay, Sarah, bottom line: How long can milk be kept out of the refrigerator before it starts to spoil?

Sarah Downs, RD: “Milk should never be left out at room temperature.

Refrigeration is the single most important factor in maintaining the safety of milk. Milk should be stored at 40° F or below. If stored above 40° F, milk will begin to develop signs of spoilage, including sour odor, off-flavor and curdled consistency.”

What if you’re not sure how long the milk has been left out? Is there a way to tell if it’s still safe to use?

Sarah Downs, RD: “When in doubt, throw it out. The general rule of thumb is to discard any perishables that have been stored above the “Danger Zone” of 40° F for more than two hours, no matter what their appearance or odor (and never taste the food to try and determine whether it’s still safe).”

What about ultra-pasteurized milk?

Sarah Downs, RD: “Ultra-pasteurized milk is heated to 280° F for a minimum of two seconds. This temperature and time combination is much more lethal to bacteria, killing virtually all of concern in milk. Ultra-pasteurized milk is also packaged under near sterile conditions, which makes recontamination with spoilage bacteria unlikely and rare. The average shelf-life of ultra-pasteurized milk products is 30 to 90 days when held under refrigeration, but only until the product is opened. Then it should be consumed within seven to 10 days to avoid spoilage.”

What’s different about the milk you see sitting at room temperature on the grocery store shelves?

Sarah Downs, RD: “Shelf stable milk has been ultra-pasteurized (UHT) and is packaged in aseptic cartons. This allows the milk to sit at room temperature in the grocery stores. However, it must be refrigerated after being opened and consumed within seven to 10 days to maintain quality and food safety.”

What advice do you have for parents to safely pack milk for their little ones in a sippy cup or lunch box?

Sarah Downs, RD: “For parents on the go, I would recommend the following options:

1. Pack milk in a lunch box or cooler with an ice pack to ensure it stays cool.
2. Purchase shelf-safe milk (make sure it has the UHT label on the package too!). Also, remember that after this milk is opened it should be treated like regular milk and kept cool at 40° F or cooler.
3. It’s important to remember that opened milk, regardless of the type, should never be left in temperatures above 40° F for more than two hours.”

Although we may not figure out who was responsible for leaving the milk on the counter, these guidelines will help us stay safe and enjoy nutritious milk!