How To Tell If Milk Is Bad (5 Spoiled Signs)

We may earn affiliate fees for purchases using our links (at no additional cost to you). Learn More.

If you’ve ever had a carton of milk go bad on you before finishing it, you know that the smell can be pretty unpleasant. But what if your milk just tastes weird or looks not quite right? How do you tell if milk is bad?

The best way to tell that milk has gone bad is when it tastes or smells sour. If your milk becomes lumpy, turns yellow, or has mold growing on it, it is no longer safe to consume and should be discarded.

Here is a closer look at the signs that your milk has spoiled and is no longer safe to drink.

How To Know If Milk Is Bad

It Has A Rotten Or Sour Smell

Spoiled milk has a very pungent sour smell that you will notice immediately. This rotten smell is caused by lactic acid bacteria as they break down and ferment your milk.

Unfortunately, despite our best efforts in the pasteurization process, some bacteria may survive the high temperatures and flourish when conditions are best for them. When milk has sat out and warmed up into the danger zone, bacteria multiply like crazy!

Fresh milk should have almost no smell, but some people describe a very mild sweet smell to it. Of course, if you’re drinking flavored milk, such as strawberry or banana milk, then you can expect the ingredients to give off a slight smell.

So, in the case of bad smells, it’s always a good idea to give your milk a quick whiff before pouring it to check to see if it’s still good.

It Has A Sour Taste

The same spoilage bacteria responsible for creating a sour smell will also give your milk a sour taste.

What does sour milk taste like? The sour taste is not like yogurt, it’s much more intense in a bad way, and your body will tell you something is off, so listen to it.

There is nothing you can do to save soured milk. It should be disposed of in the toilet or down the sink while running water. If you don’t run water while pouring it out, it’s possible some of the sour milk remains in your drain and will start to smell in your kitchen.

On the same note, pouring liquids into the trash is a bad idea. One small tear in the bag and you’re going to regret the decision instantly.

It Is Lumpy

Unlike heavy cream, where fats can separate easily, lumpy milk indicates that it has gone bad. You will notice that your milk is no longer smooth and may either have a grainy texture to it or large lumps.

The lumpiness is caused by the curdling of the milk proteins as they start to break down. When you see lumps in your milk, it’s best to just discard it and get a new carton.

It’s Turning Yellow

The interesting thing about milk that’s turning yellow is that it could be caused by fats in the milk if it was previously frozen. But if your milk has never been in a freezer, there’s a good chance that it has spoiled.

The yellow color in fresh milk indicates that it is separating as it decomposes. That creamy white liquid breaks down into previously unseen nutrients in the mixture.

I don’t recommend using yellow-tinted milk at all, not even for cooking. At this point, there could be a lot of nasty bacteria that could make you sick.

It Has Mold

Like most perishable food products, milk will grow mold on the surface and the inside walls of your milk container if given a chance.

No brainer here, if you see any signs of mold, do not use it for anything.

To prevent mold spores from spreading around your kitchen, place the entire container in two plastic bags, seal it, and freeze it until garbage day. The reason for two plastic bags is so that if the container bursts while freezing, which is likely, it should hold any liquid that escapes the container.

Bad Milk FAQs

Does Milk Expire On The Date?

The date labeled on milk is often not an expiration date but rather a “sell by” or “best before” date. The milk may be safe to drink after this date, but it may not taste as fresh. You should pay close attention, and if you notice any signs of spoilage, do not consume it.

Will Spoiled Milk Make You Sick?

Yes, spoiled milk can make you very sick. It’s important to realize that milk is a perfect breeding ground for harmful bacteria, such as listeria, salmonella, and E. coli. These bacteria can cause serious food poisoning.

What Are The Symptoms Of Drinking Spoiled Milk?

You may experience nausea, stomach cramping, and vomiting if you accidentally drink spoiled milk. However, these symptoms are also common when you have lactose intolerance. If you are unsure if your symptoms are due to spoiled milk or lactose intolerance, it’s always best to speak with a doctor.

Written By Justin Micheal

Justin is not just the creator but also an author and editor for KitchenSanity. He does the majority of the cooking at home with his wife. His friends and family look forward to eating his delicious creations, which often leads to many questions about how they can replicate his meals at home. In his writing, he shares his passion and knowledge as a home chef from his kitchen to yours.