Freezing Milk Makes It Unpalatable (Here’s Why)

Published Categorized as Food
Milk on a blue backgroundxamtiw /Depositphotos

Thawed milk is milk that’s left undranken. Take a gander below to find out why.

Milk, a highly perishable product, must be kept in the refrigerator and should never be left out at room temperature for longer than 1-2 hours, or it will spoil. Even though milk needs cooling, it doesn’t do well when frozen and thawed for the reasons that we’re about to discuss below.

Frozen milk becomes unpalatable. When milk is thawed, the solids separate from the water. The fat rises to the top and the proteins clump together—leaving behind a bland, watery liquid with puddles of fat on the surface and clumps of protein in the liquid.

Generally speaking, this change cannot be reversed, at least not with the equipment in the home kitchen. In dairy plants, milk is pumped into jugs or containers and forced at high pressure through small nozzles that break up its structure and make it consistent again.

It’s also why most cooks, when they come back home from a trip to the farmer’s market or bring back a few jugs of milk too many from a sale at the supermarket, opt for other methods of preservation.

We will get to the best of them momentarily.

Why Milk Doesn’t Freeze Well

Milk is a complex liquid, Peter Barham, physicist at Bristol University, explains to readers of The Guardian.

“It consists of many small droplets of fat,” he writes, “each surrounded by a membrane that helps to keep them suspended in a solution of proteins and sugars in water.”

A fine balance keeps this liquid homogeneous, says Barham, and freezing disturbs it. When you freeze milk, the liquid water, which makes up roughly 90% of its contents, turns into ice crystals.

These ice crystals are sharp, and they pierce the membranes that keep the fat globules suspended in the water. As a result, the fat escapes from the droplets, rises to the top, and pools in puddles (cooled, milk fat solidifies, much like the butter made from it).

Milk is also acidic. It contains bacteria that feed on the sugar (lactose) in it, spitting out acid (lactic acid) as a byproduct of their feast. These bacteria are most active at room temperature. Their activity slows down, but doesn’t grind to a halt, in the fridge.

Older milk is more acidic than fresh because the bacteria have converted more of the sugars to acids. You can verify this at home with a carton of store-bought milk and a litmus test paper strip, with which you can measure the pH level of the liquid.

When you freeze milk, the liquid water turns into ice crystals. The lactic acid is no longer evenly dispersed in a liquid; it is concentrated in spots on the crystals. This causes some of the casein proteins that come into contact with it to coagulate and curdle.

If you freeze milk quickly, when it is still fresh, less of the fat will separate and fewer proteins will curdle. The quicker the freezing, the smaller the ice crystals. The fresher the milk, the lower its acidity.

The problem with this is that most of us get our milk from the supermarket, when it’s already past its prime. Moreover, milk freezes as fast as our freezers will allow, and household appliances cannot match the freezing speed of their commercial counterparts.

Now, if you owned a milk plant, this wouldn’t be an issue because you’d have a homogenization machine. These things pump hot milk at high pressure through small nozzles, which breaks it down and causes its constituents to homogenize once again. Alas, you don’t.

Try as you might, but if you freeze a carton of milk, chances are it will separate and curdle. (Down the drain, into the toilet, or in the watering can for your garden it goes!)

The Three Very Best Ways to Preserve Milk

Yogurt

Here’s something you hadn’t thought about before you stumbled upon this article and read it this far: Making your own yogurt at home is easier to do than you probably think.

All you need is 1 gallon (4.55 l) of milk and ½ a cup of plain yogurt (for bigger batches, treat this as a ratio and adjust accordingly). Whole milk makes for the creamiest, most decadent homemade yogurt. However, those of you who want their yogurt on the leaner side can go for 2% milk, 1% milk, or skim milk just as well.

In a Dutch oven with the lid removed, scald the milk over medium-high heat. When the milk starts to bubble and foam, keep it on the stove for 2-3 minutes, stirring to keep it from boiling over and prevent it from scorching at the bottom of the pot (which will impart your yogurt with the unpleasant taste of burnt milk).

Cool the milk by filling your sink with cold water and resting the Dutch oven in it for 4-5 minutes. Remove the Dutch oven from the sink, stir in the yogurt with the milk, then whisk together to incorporate. Cover the vessel with a tablecloth or a few large enough towels and rest, in a warm place in the kitchen, for 4 to 24 hours; the longer the resting period, the tangier the yogurt.

Poured into washed mason jars and stored in the fridge, homemade yogurt keeps for 10 to 14 days.

Cheese

You opened up to the idea of homemade yogurt… While you’re at it, why not contemplate homemade cheese?

From mozzarella to cheddar, the varieties of cheese that can be made at home are limited only by the cook’s experience and ingenuity. However, the easiest cheese to get started with is lemon cheese.

You will need 1 gallon (4.55 l) of whole milk, the juice of 6 lemons (about ½ a cup), and non-iodized salt (cheese salt, kosher salt, or flaky sea salt). Also, a Dutch oven, a spoon, a colander, and butter muslin (or fine cheesecloth).

Bring the milk to room temperature by leaving it out for 15 minutes.

Fill the Dutch oven, on the stovetop and with the lid removed, with the milk. Bring to heat over medium-high, wait until the milk starts to bubble and foam, then start stirring continuously so that it doesn’t boil over or scorch. Do this for 2-3 minutes before proceeding to the next step.

Add the lemon juice to the steaming milk. Start stirring, gently and slowly, for another 1-2 minutes. Remove the pot from the heat, cover with the lid, and rest it on the counter for 15-20 minutes.

In the kitchen sink, with the muslin in a colander, strain the cheese curds from the liquid whey. Tie the curds in the muslin tightly to form a cheese ball. Hang by the ends of the muslin on the faucet and let the wrapped cheese drain for 2-3 hours.

Untie, unwrap, and salt the cheese to your liking. Transfer to a food storage container and refrigerate. Once the cheese has cooled, it is ready to be enjoyed; it will keep in your fridge for 10 to 14 days.

Ice Cream

For the reader with a sweet tooth who wants to preserve milk, we suggest homemade ice cream.

The ingredients are 1 cup of whole milk, 2 tablespoons of white sugar, 3 cups of ice (from the freezer), and ⅓ cup of non-iodized salt (kosher salt or sea salt).

In a bowl, whisk together the milk and the sugar. Pour the contents in a smaller freezer bag and seal tightly.

Wash the bowl. Add ice and mix, by hand, with the salt. Pour the contents in a larger freezer bag. Put the smaller bag with the milk inside it. Seal and shake energetically for 10 minutes until the consistency has turned to cream.

Unseal, serve, and enjoy. Or transfer to an airtight food storage container and freeze, where your homemade ice cream will keep its best qualities for up to 1-2 months.

By Jim Stonos

When Jim isn't in the kitchen, he is usually spending time with family and friends, and working with the HCW editorial team to answer the questions he used to ask himself back when he was learning the ropes of cooking.