We are often told not to freeze dairy products for various reasons. But does this mean we should never freeze dairy? Is there a difference between freezing milk and freezing butter?
Milk, although it can be frozen, may undergo protein coagulation (proteins will clump together), fat separation (fat will separate out of emulsion), fat auto-oxidation, and other changes that can result in unfavorable texture and flavor differences, once the milk is thawed. Still, although it may depend on the precise temperature the milk was stored at, as well as the length of time, you’d be surprised what a vigorous shaking will do, and you may or may not notice textural or taste differences.
Soft cheese will separate during freezing and hard cheeses will be crumbly once thawed. Whether this is acceptable depends on the intended use of the product. For example, if you freeze cheddar or Swiss cheese, it will have a crumbly texture once thawed, but may still work fine in cooking situations where the cheese will be melted.
Prepared foods that rely on a lot of dairy sometimes cannot be frozen, and other times will do well. Custards will separate and be ruined by freezing. Cheesecake, on the other hand, does fine in the freezer, as long as it is thawed slowly in the refrigerator before serving (do not freeze a cheesecake with a topping).
Some of the problems of freezing dairy can probably be overcome on a commercial basis if there were interest in doing so.
How a dairy product behaves during freezing has a lot to do with its water content, and how other components separate during freezing. Butter, however, contains very little water, less than 20%, and the water that is present exists in tiny little droplets that are distributed throughout the butterfat and other solids.
Homogenized milk is the other way around, the fat and other solids is distributed evenly throughout the water. Basically, this means that freezing doesn’t have much of an observable effect on butter. This doesn’t mean there is no effect. When it is frozen, at what temperature, and for how long, can certainly affect the outcome.
However, for the most part, if you have extra butter, you can pop it in the freezer and store it for up to 6 months, with no problem. When you need to use it, take it out and put it in the fridge. Now, butter, even when frozen, can easily absorb flavors during storage. So, the longer you store butter in the freezer, the better the chance of it picking up some off flavors.
Although you can place a package of butter sticks right in the freezer and freeze it without much problem, if you want to store it for a long time, you should over-wrap the package tightly with plastic wrap, or place it in a freezer bag, to help keep out bad odors. Unsalted butter, it is said, can be frozen for longer periods than salted butter. Certainly, the freezing point of the water in the butter will be lowered by the addition of salt. For practical purposes, this probably makes little difference for casual home storage. It is difficult to say how long is too long to store butter, but most sources indicate 3 to 6 months for the best results.