Catching a whiff of spoiled milk is enough to ruin even the most voracious appetite, but if you find yourself stuck with a carton of it, you may want to think twice before pitching it.
Contrary to popular belief, spoiled milk may have a place in your next culinary pursuit. Not to mention, using spoiled milk in recipes is a great way to reduce food waste.
This article explains what spoiled milk is, whether it’s safe to drink, and ways you can use it.
What is spoiled milk?
Spoiled milk is the result of an overgrowth of bacteria that compromises the quality, flavor, and texture of milk.
Since the late 1800s, the vast majority of commercially produced milk is pasteurized. The pasteurization process kills many of the most harmful strains of bacteria known to cause foodborne illness, including E. coli, Listeria, and Salmonella.
However, pasteurization doesn’t eliminate all types of bacteria. Plus, once you open a carton of milk, it’s exposed to additional bacteria from the environment. Over time, these small bacterial communities can multiply and eventually cause your milk to spoil.
Signs your milk has spoiled
When milk begins to spoil, it develops an unpleasant, rancid odor. The scent is hard to miss and gets stronger with time.
The taste also begins to change, as the natural sweetness of fresh milk is quickly replaced by a somewhat acidic or sour flavor.
With enough time, the texture and color of milk that has spoiled will change as well. It may begin to develop a slimy, chunky texture and dingy, yellow color.
The rate at which milk spoils depends on many factors, including the number of spoilage bacteria present, temperature at which the milk has been stored, and light exposure (1).
If you’re unsure whether your milk has spoiled, start by sniffing it. If it doesn’t smell off, try a small sip before pouring a full glass or adding it to your cereal.
Milk spoils due to an overgrowth of bacteria that compromises its quality. You know your milk is spoiled if it has an unpleasant odor or taste or changes texture.
Slightly different from sour milk
The terms spoiled and sour are often used interchangeably to describe milk that has gone bad, but there may be a subtle difference between the two — depending on who you ask.
Spoiled milk usually refers to pasteurized milk that smells and tastes off due to the growth of bacteria that survived the pasteurization process. Most of these bacteria aren’t considered health-promoting and could make you sick (2).
On the other hand, sour milk often refers specifically to unpasteurized, raw milk that has begun to naturally ferment.
Much like spoiled milk, the fermentation of raw milk occurs due to various species of lactic-acid-forming bacteria, a small percentage of which are considered probiotics and may offer minor health benefits (
That said, the potential benefits of raw milk don’t outweigh its risks. It’s typically not recommended to consume raw milk in any form — fresh or sour — due to the high risk of foodborne illness (
Spoiled milk usually refers to pasteurized milk that has gone bad, while sour milk may refer to raw milk that has begun to ferment.
Risks of drinking spoiled milk
Most people are immediately turned off by the foul smell and taste of spoiled milk, which makes the decision about drinking it a relatively easy one.
However, even if you can get past the unpleasant taste, drinking spoiled milk isn’t a good idea. It can cause food poisoning that may result in uncomfortable digestive symptoms, such as stomach pain, nausea, vomiting, and diarrhea.
You don’t need to worry if you accidentally ingest a small sip of spoiled milk, but avoid drinking it in large — or even moderate — quantities.
Drinking spoiled milk can cause digestive distress, such as vomiting, abdominal cramping, and diarrhea.
Can still be useful in the kitchen
Though you shouldn’t drink spoiled milk, it’s far from useless.
If your milk is very old and has started to curdle, become slimy, or grow mold, it’s best to throw it out. Yet, if it’s just a little off and slightly acidic, there are several ways to use it.
Try using slightly spoiled milk in one of the following culinary applications:
- Baked goods. Substitute spoiled milk for regular milk, buttermilk, yogurt, or sour cream in recipes like biscuits, pancakes, scones, and cornbread.
- Soups and stews. A splash of spoiled milk can help thicken and add richness to soups, stews, and casseroles.
- Salad dressing. Use sour milk to make creamy dressings like ranch, Caesar, or blue cheese.
- Cheesemaking. Use sour milk to make homemade cottage or farmer’s cheese.
- Tenderize. Use sour milk to marinate and tenderize meat or fish. You can also soak uncooked, whole grains in it to soften them.
Additionally, you can add spoiled milk to homemade face masks or a bath to soften your skin. Still, you may want to mix it with essential oils or other fragrant ingredients if you find the smell overbearing.
Spoiled milk can replace buttermilk or sour cream in baked goods. It can also be used to tenderize meats or added to soups, casseroles, or salad dressings. You can likewise use it in certain cosmetic applications to soften your skin.
The bottom line
Spoiled milk is the result of an overgrowth of bacteria that causes changes in taste, smell, and texture.
Drinking it may make you sick, but cooking with it won’t, as long as it’s just a little off.
Using your slightly spoiled milk in innovative ways can also help you reduce food waste.
The next time you notice that the milk in your fridge is starting to go bad, don’t throw it out right away. Instead, try using it in pancakes, biscuits, or as a thickener for soups and stews.