What happens when milk turns yellow?

The age-old questions asked in kitchens across the UK: Does this milk smell off? Does milk ever smell good? Can you freeze it? We've found out the truth behind the last of these milk-based mysteries.

According to the Dairy Council for Northern Ireland (DCNI), yes, it is possible to freeze milk, but with certain precautions.

Firstly, it is crucial to freeze milk that is still within its ‘use by’ date. If it’s been open for a few days, and you’re already giving it an inquisitive sniff, it’s probably too late.

The biggest danger when it comes to freezing milk is that it expands. For this reason you should never freeze it in a glass bottle because it will crack. Giving the carton extra space in the freezer also caters for this expansion, and stops it getting wedged in the freezer.

Another thing to bear in mind is that milk turns yellow when frozen, so do drink yellow milk but don't eat yellow snow.

Whole milk doesn’t freeze as well as semi-skimmed because of its higher fat content. This is due to fat requiring a much lower temperature than the -18 degrees that typical household freezer can offer.

For years, Mumsnet has been the platform for milk-freezing-based debate. Here are some dos and don’ts given by mums up and down the country:

1. Freezing the milk upright deals with potential leakage issues.
2. Defrosting can take an eternity in the fridge, so put it in cold water or on the draining board if time is of the essence. 
3. Giving it a good shake once defrosted gets rid of the watery layer which can form at the top.
4. Once it has defrosted, it’s important to use it within a couple of days. Freezing it doesn’t magically extend its life when it’s back in liquid form. 
5. Organic milk doesn’t go as yellow as non-organic.
6. Do not defrost in the microwave, or use any other source of heat. 
7. Like milk, butter also freezes well.

Beware though; unlike milk, some cheeses do not fare well when frozen. While harder cheeses will probably be fine, softer cheeses, such as cottage cheese or cream cheese, will not.

Even hard cheeses can go crumbly when frozen, so the DCNI recommend grating your cheese before freezing and storing it in an airtight food bag. This is perfect for sandwiches, toppings and sauces, one Mumsnet commenter said.

This article was originally published in December 2017

The color of breast milk is usually yellow, white, clear, cream, tan, or blue-tinged. However, at some point during your breastfeeding experience, you may be surprised to find that your breast milk can be other colors as well.

Depending on what you eat or drink, your breast milk may look as though it has a green, pink, or red tint. Sometimes, a little bit of blood may even make it's way into breast milk giving it a brown or rust color.

You may notice that the color of your breast milk changes over time. But, It can also change during the course of a day or even within the same feeding. It may get you wondering what color breast milk should be and what's normal? Here is what you need to know about the colors of breast milk and what they mean. 

During the first few weeks after you have your baby, your breast milk changes quickly. Not only in composition and amount, but also in color. So, what color is breast milk? Here are the normal changes in breast milk color by stage. 

Colostrum is the first breast milk that your body makes. You only make a small amount of colostrum, but it's concentrated and highly nutritious. While colostrum is sometimes clear, thin, and watery, it's more often yellow or orange and thick. The high levels of beta-carotene in colostrum give it its dark yellow or orange color.

After the first few days of colostrum, the production of breast milk increases and your body begins to make transitional milk. During this two week transition period, the color of breast milk typically changes from yellow to white as your milk comes in. 

After about two weeks, your body reaches the mature milk stage. Mature breast milk changes in appearance based on how much fat it contains. 

• Foremilk: In general, when the mature milk begins to flow out of your breast at the beginning of a feeding or pumping session, it is thinner and lower in fat. This milk is called the foremilk. Since foremilk is thin, it tends to look clear or bluish.
• Hindmilk: As you continue to pump or breastfeed, the fat content in your milk goes up. As the fat increases, breast milk turns into creamier milk called hindmilk. Hindmilk has a thicker white or yellow appearance. 

Certain foods, herbs, nutritional supplements, and medications can change the color of your breast milk. These additives can also affect the color of your urine and your baby’s urine. 

Although it might be shocking and scary to see, it's normal for breast milk to vary in color and tint. These changes are usually diet-related and not dangerous. Here are some of the different colors of breast milk. 

You may notice a green tone to your breast milk after you eat green foods or foods that contain green dyes. Your breast milk might take on a greenish color if you drink green-colored beverages like Gatorade, eat a good amount of green vegetables, such as spinach or seaweed, or add certain herbs or vitamin supplements to your diet.

You may notice pink, orange, or red-tinged breast milk after eating foods that are naturally these colors, or after having foods or drinks that contain red, yellow, or orange food dye. Beets, orange soda, and red or orange fruit drinks can all cause your milk to turn different shades of pink, red, and orange.

If blood from inside your breasts leaks into your milk ducts, your breast milk may look brown, dark orange, or rust-colored. When breast milk looks like dirty water from an old rusty pipe, it's called rusty pipe syndrome.

Blood can also get into your milk if you have cracked nipples. It may look like red or pink streaks. Don't panic. You do not have to throw away your breast milk or stop breastfeeding. A little bit of blood in your breast milk will not harm your child. In most cases, the bleeding will go away on its own in a few days. If it doesn't, and you continue to notice blood in your breast milk after a week, check with your doctor.

The production of black breast milk is linked to antibiotic Minocin (minocycline). Minocin also causes darkening of the skin. The use of Minocin is not recommended while you're nursing. That's why it's so important that you always let your doctor know you're breastfeeding before taking any medication.

When you pump and store breast milk, it can change a little bit. In the refrigerator, breast milk may separate into layers. There may be a thick, white or yellow creamy layer on top, and a thinner clear or blue-tinted layer on the bottom. You don't have to worry. It's normal, and it doesn't mean the milk went bad.

It's just that when it sits, the fat rises to the top. When you're ready to use it, you just have to mix the layers by gently swirling the bottle. Breast milk can also change color in the freezer. Frozen breast milk may look more yellow.

Most of the time, any change in the color of your breast milk is due to something that you ate, and it's likely nothing to worry over. However, if you have any concerns about your breast milk, you should feel comfortable contacting your healthcare provider. Your doctor or a lactation specialist will be able to listen to your concerns, evaluate the situation, and have you come in for an examination, if necessary.

Most breastfeeding moms don't notice the slight variations in the color of their breast milk unless they pump often or their baby spits up a little breast milk with a hint of color. If this is your first experience with breastfeeding, changes in your breast milk may alarm you.

Certainly, noticing your milk has turned green or orange or seeing a bit of blood in it can make you wonder if it is still healthy for your baby. Knowing the reason behind the color change and understanding that it's a common occurrence that's usually not dangerous can be reassuring.