Unless you are drinking flavored milk, you always expect milk to be white. For that reason, it usually becomes a sign that any milk that isn’t white must be out of date or contaminated. That leads to the question, of course, of why is milk white?

The answer is simple and has everything to do with the way light is reflected off the milk while absorbing no light. Milk is mostly water, approximately 87% water. Although water is colorless, the other parts that make up the milk (fat, protein, lactose, minerals and vitamins) help influence the color being white. Fat and protein reflect light wavelengths, without absorbing the wavelengths, thus making the milk white in color.

When you drink skim milk, you may notice that it has a blue hue to it that most kinds of milk do not have. This is for the same reason, as skim milk has less fat in it than whole and 2% milk, it absorbs a little more light and thus looks bluer than the other kinds of milk.

However, the color of your milk can indicate whether or not the milk has gone bad and is safe to drink. There are a few ways you can use your senses, sight included, to test whether or not your milk has gone bad easily.

Related: What Milk Tastes the Best?

How to Tell if Your Milk Has Gone Bad

If milk should be white, then can you tell if it’s gone bad based on its color? As it has become more widely known that “best before” dates should be taken as estimates and not as law, learning to tell if your milk has gone bad is essential. Milk can grow bacteria and cause illness when it goes bad from either expiry or being kept in a warmer temperature that allows it to grow bacteria.

Keeping an eye on your milk is essential to ensuring that you don’t end up getting sick from spoiled milk. There are a few ways to tell if your milk has gone bad or not.

● What Color is the Milk?

As discussed, milk should be a pure and clean white color. When the color of the milk changes to a more pale/faded white or yellowish color, there is a strong chance the milk is not safe to consume. You do not want to drink milk that is no longer the pure white color you expect it to be.

The best way to test this is to pour some of the milk into a clear glass and inspect it in a brightly lit room. Anything but white? It’s gone bad and isn’t safe to drink.

● What Does it Smell Like?

This way is by far the easiest way to tell if your milk has gone bad. The smell of spoiled milk is unmistakable, and any unusual odor from the milk is a tell-tale sign that the milk has gone bad. Often, all you need to do is just open the carton or jug, and you can tell right away. Milk shouldn’t have an unpleasant smell.

● What is the Consistency and Texture of the Milk?

Milk should always be a smooth and thin liquid, free of any chunks if your milk has any lumps or is a yellowish color than it’s more than likely gone bad. Just like color, testing the consistency is incredibly easy. Pour some of the milk into a clear glass, and if it takes on the consistency of yogurt or cottage cheese, or if it begins to curdle at all, the milk is not safe to consume.

● How Long Has it Been Sitting at Room Temperature?

Milk is not a shelf-stable food or beverage. Aside from powdered milk, most kinds of milk shouldn’t be kept at room temperature for any length of time. This is because milk can very quickly grow bacteria that can cause illness and isn’t safe to consume. If you were thawing milk on the counter or forgot it overnight outside of the fridge, it’s more than likely not safe to drink.

Any one of these can be a sign that your milk has spoiled. Ensuring that you keep an eye on the color, consistency, and smell of your milk is the best way to avoid consuming spoiled milk. The “best before” date is not an exact science, but a couple of simple tests can determine the safety of the milk before you consume it. Ensuring that your milk is stored properly and kept at the proper temperature is the best way to keep your milk from spoiling earlier than it needs to.

If you have spoiled milk, you don’t have to throw it away! There are some ways that you can use sour milk in baking, cooking and in other ways that are easy to find online. Some recipes even call for “soured milk.” However, be careful to read the instructions on the recipe, and once the milk starts to stink and separate, it’s unsafe to use, and there is nothing else you can do with it.

What Can Happen if You Drink Spoiled Milk?

Drinking spoiled milk is incredibly ill-advised, as it can and often does cause food poisoning. Signs that you got food poising can be symptoms such as,

  • Stomach pain
  • Nausea
  • Vomiting
  • Diarrhea

A single accidental sip is incredibly unlikely to cause you to get food poisoning. However, if you drink even moderate amounts of spoiled milk you are incredibly likely to get sick because of it.

What Does the Milk Lable Colors Mean?

The colors on the labels of your milk aren’t completely meaningless, though the answer is a lot simpler than it may first appear. These labels may be the actual carton color or the cap on the jug, but akin to the clips on bread, all have different meanings corresponding to their colors.

Each different color represents a different percentage of fat in the milk, and it’s that simple. The breakdown often looks like this.

  • 2% Milk is Labelled Blue (and sometimes yellow)
    • For the most part, a blue cap or label indicates 2% milk, but certain brands use yellow instead to represent 2%
  • 1% Milk is Green
  • Whole Milk is Labelled Red
  • Skim Milk is Labelled Purple

This is only true for cow’s milk, as milk substitutes come in an array of colors without the cap/label distinguisher. This coloring system is the most common among nearly all milk brands and makes for easy spotting at the grocery store for your preferred milk. Additionally, this system helps grocery store employees stock the refrigerator much quicker than having to read each label individually. However, this is not a uniform system, and thus, you should always double-check before you purchase.

Milk should always be white unless it is flavored, of course. Grey or yellowing milk is obviously dangerous and unsafe to drink. Telling if the color of your milk indicates that it has spoiled is incredibly easy for this reason as the simple test is, if the milk isn’t white, then it’s likely spoiled. Though soured milk can be used for baking, actually spoiled milk will cause illness, and it is advised you avoid ingesting milk that has gone bad.

Finally, the reason kinds of milk have different colors for their labels has all to do with the fat percentage. Though alternatives don’t follow any color code, and some brands may break the pattern. Usually, though, milk label colors can help you find your preferred kind of milk quickly and efficiently while out shopping.