Here's How Long Soy Milk Lasts After Opening

Soy milk rose in popularity in the 20th century after manufacturers in the good old U.S.A. figured out how to produce this beverage — which hails from China — in such a way so that the actual soy bean flavor isn't as pronounced. Now it's everywhere (unfortunately, for the rain forests), sold in grocery stores across the country (so you can easily make kong-guksu at home) and ultimately triggering the on-going milk wars with the dairy industry. But if you have a carton of soy milk in your fridge, you might be wondering exactly how long you have to finish an open container of the stuff before it starts to go bad.

Soy milk that has been properly refrigerated and handled can last up to 10 days once opened. If it has been refrigerated at the store it must continue to be kept cold at home. But the shelf-stable variety, which is sold in cartons on regular supermarket shelves, can be stored in a cool, dark pantry for three to four weeks after the date printed on the label. Once opened, however, it must be refrigerated and the clock will start ticking on the 10 days you have to finish it.

As mentioned, whether or not it was purchased as a shelf-stable product, soy milk must be refrigerated once it's been opened and it shouldn't be left out on the counter for more than two hours at a time. Nor should your soy milk be stashed just anywhere in the fridge. While it would be convenient to keep it in the fridge door, fluctuations in temperature that occur every time the refrigerator is opened could cause early spoilage.

You could freeze soy milk, but it will change the texture and consistency of the liquid, causing separation. It's not the most appetizing transformation, but the milk will still be safe to consume so you could still use it for cooking or pour it into your morning coffee. You will likely have to transfer the milk to an airtight, freezer-safe vessel, like these plastic freezer containers with twist top lids.

Soy milk can start to spoil even before the 10-day timeframe is up, so here are some signs to look out for once the end is nigh. First, the carton might start to bulge as a result of bacteria that has worked its way into the container and begun emitting gas. If you go to pour yourself a glass and notice that the soy milk has turned lumpy, that's another indication that the contents have gone bad. Also, if it smells rancid and sour, the spoilage process has already begun.

There is also the color and texture to contend with. Fresh soy milk is smooth, creamy, and just off-white. If you notice any changes to these factors, like curdling, or a darkening of the color, it might be best to err on the side of caution and dump it down the drain. Finally, if you see mold floating in your milk, that's a definite sign that it has reached the end of its shelf life.