Is soy milk OK if left out overnight?

Soy milk has become a popular plant-based milk alternative for many people. But because it’s made from soybeans instead of dairy, some people wonder if the rules for storing soy milk are different than for regular milk. Specifically, is it safe to leave soy milk out on the counter overnight, or will it spoil?

The Short Answer

In general, it’s not recommended to leave soy milk out at room temperature overnight. Like dairy milk, soy milk can grow bacteria and spoil if left unrefrigerated for too long. For best quality and food safety, store soy milk in the refrigerator and use within about one week of opening.

Examining the Differences Between Soy Milk and Dairy Milk

To understand why soy milk shouldn’t sit out overnight, it helps to first examine the differences between soymilk and dairy milk:

• Soy milk is made from soaked, ground soybeans mixed with water. Cow’s milk comes from cows.
• Soy milk does not naturally contain lactose, the milk sugar found in dairy milk.
• Soymilk is naturally lactose-free, making it a popular choice for those with lactose intolerance.
• Soy milk is cholesterol-free and low in saturated fat, while whole dairy milk contains cholesterol and saturated fat.
• Both contain proteins, carbohydrates, vitamins and minerals, but in different amounts.

While they have their differences, soy milk and regular milk are nutritionally comparable. But when it comes to food safety, soy milk isn’t all that different from dairy milk. Both can spoil and host harmful bacteria when left out at room temperature.

Why Refrigeration is Important

Milk of any kind left out at room temperature provides the ideal breeding ground for bacteria. Here’s why:

• Bacteria thrive and multiply rapidly between 40°F and 140°F.
• Room temperature falls right in the middle of this “danger zone.”
• Cold refrigerator temperatures keep milk safely out of the danger zone.

Pasteurization is a process that heats milk to high temperatures to destroy pathogens. Both dairy milk and soy milk sold commercially are pasteurized to kill harmful bacteria for safety and extend shelf life. However, pasteurization doesn’t make milk shelf-stable. Refrigeration is still required to limit bacteria growth and keep it fresh.

How Long Can Soy Milk Sit Out?

Dairy milk and soy milk should spend minimal time at room temperature. Here are some guidelines:

• 1-2 hours: Best if refrigerated again quickly.
• 3-4 hours: Quality starts to decline as bacteria numbers increase.
• Over 4 hours: Discard milk; potential bacteria contamination unsafe.

Leaving soy milk out on the kitchen counter overnight puts it well over the 4-hour unsafe time limit. So regardless of whether it’s dairy or soy, milk should not be left unrefrigerated for long periods.

Signs Soy Milk Has Spoiled

If you’re unsure whether that soy milk left out is still good, check for the following signs of spoilage:

• Smell: Spoiled soy milk has a distinct sour, bitter odor.
• Taste: Bad or “off” flavors.
• Color: Normal is creamy white to light brown, but spoiled milk may look yellow or grey.
• Texture: Thick, chunky, gelatinous or curdled.
• Mold: Check bottom of container for fuzzy mold colonies.

If your soy milk exhibits any of those signs, err on the safe side and throw it out. Don’t risk getting sick by drinking spoiled milk.

Tips for Storing Opened Soy Milk

Once opened, soy milk should be stored in the refrigerator. Here are some tips for keeping it fresh and safe:

• Store in original container tightly sealed.
• Keep temperature at 40°F or below.
• Use within 5-7 days of opening.
• Don’t return soy milk to the fridge if left out more than 2 hours.
• Watch for expiration date and don’t use after.
• Check for signs of spoilage before drinking.
• Avoid repeated warm-ups that could promote bacteria growth.

Also, soy milk can absorb flavors and odors. Store it separately from strongly scented foods.

Can Soy Milk be Frozen?

Freezing is a great way to extend the shelf life of soy milk and have it ready to thaw and drink later.

Here are some freezing tips for soy milk:

• Freeze in original container or covered freezer-safe container.
• Leave room for expansion as contents freeze.
• Agitate gently after thawing for even consistency.
• Use within 1 week after thawing in refrigerator.
• Don’t refreeze thawed soy milk.

Freezing can cause some separation, so shake containers gently before use. Soy milk can be frozen for 2-3 months.

The Bottom Line

Soy milk should not sit at room temperature overnight. Like dairy milk, leftover soy milk should be properly refrigerated. Close the container tightly, store at 40°F or below, and use within a week of opening. Discard any spoiled milk that smells bad or looks curdled. For maximum freshness and food safety, soy milk is best kept chilled in the fridge or freezer.

Nutrition Comparison of Soy Milk and Dairy Milk

Here is a nutritional comparison between 1 cup of soy milk and 1 cup of 2% fat cow’s milk:

Nutrient	Soy Milk	Cow’s Milk (2%)
Calories	80	122
Fat	4g	5g
Saturated Fat	0.5g	3g
Carbs	4g	12g
Protein	7g	8g
Calcium	301mg (30% DV)	293mg (29% DV)
Vitamin D	101 IU (25% DV)	124 IU (31% DV)

DV = Daily Value. Data from FDA Nutrition Facts labels.

While cow’s milk naturally contains more protein, calcium and vitamins D and B12, many brands of soy milk are fortified to provide comparable nutrient levels to dairy milk. Both can provide important nutrients, though soy milk has less saturated fat.

Using Soy Milk in Cooking and Baking

Soy milk can be used as a substitute for cow’s milk in many recipes. Here are some tips:

• Use plain, unsweetened soy milk.
• 1 cup soy milk substitutes for 1 cup dairy milk.
• Reduce baking powder or soda by 1/4 tsp per cup of soy milk.
• Add 1-2 tsp oil per cup soy milk in baked goods recipes.
• Soy milk thickens at higher temperatures, so adjust for sauces.
• Mix soy milk with non-dairy yogurt or smoothies.
• Use in cream soups, pancakes, oatmeal, etc.

Soy milk’s natural sweetness and creamy texture work well in coffee drinks, smoothies, desserts, cream sauces and more. Adjust recipes when necessary to reach optimal results.

Potential Health Benefits of Soy Milk

Soy milk may offer some health benefits:

• Heart health: Soy protein lowers LDL cholesterol levels, reducing heart disease risk.
• Cancer prevention: Soy isoflavones may block tumor growth and inhibit cancer cell progression.
• Bone health: Soy isoflavones help maintain bone density and may reduce osteoporosis risk.
• Menopausal symptoms: Soy isoflavones act as weak estrogen to help relieve hot flashes, vaginal dryness.
• Brain function: Soy isoflavones may improve memory and cognition for menopausal women.

However, more research is needed to confirm some of these proposed health benefits in humans. But soy milk can be part of a healthy diet, in moderation.

Possible Concerns About Drinking Soy Milk

Soy milk is safe for most people, but there are some considerations:

• Due to estrogen-like effects, soy may be contraindicated for breast cancer patients or survivors.
• Soy allergies or sensitivities can cause stomach issues after consuming soy milk.
• Soy milk lacks vitamin B12 naturally, so opt for fortified brands.
• Phytates in soy can hinder mineral absorption. Most soy milk is fortified to compensate.
• Drink in moderation. Too much soy may impact hormones, thyroid function.

Those with soy allergies, breast cancer, thyroid issues or other concerns should speak to a doctor before adding soy milk to their diet.

The Bottom Line

Soy milk offers a tasty plant-based alternative to dairy milk. But whether you opt for soy, almond, coconut or dairy milk, they all require refrigeration after opening. Leaving soy milk out overnight can allow bacteria to multiply to dangerous levels that may cause food poisoning. For food safety and optimal quality, drink refrigerated soy milk within a week and don’t leave it sitting out for more than 2 hours.