Using Previously Frozen Milk for Culturing


Whenever a food product is produced, whether through bringing ingredients together into a composed dish or using a single-ingredient cultured food, there is one factor that affects the end result above all else: the quality of the ingredients.

There's one rule of thumb that applies just as strongly in the world of single-food cultured products as it does with a fresh vegetable salad: the fresher the ingredients, the better the flavor.

So, when it comes to cultured dairy products, the fresher your milk is, the better your end product will be, all other factors being equal. And because so many people who culture their own dairy already know this, they often will seek out locally produced milk and freeze it to keep it as fresh as possible or because they will only have access to it for a season.

The good news is that this is fine. The bad news is that freezing will not keep milk forever and it can change some of its properties, which thereby can change the cultured dairy products that are produced from it.

Negative Effects of Freezing

Some alterations of the milk you may find from freezing include:

Separation. Depending on how you went about freezing your milk, you may notice a separation of the fat globules from the rest of the milk in both cow and goat milk. This is often more pronounced in cow milk as goat milk is naturally homogenized. The separation can be caused by a few factors:

  • a natural separation in cow milk due to the time it takes the milk to freeze;
  • a weakening of the membrane surrounding the fat globules, which causes an easier separation;
  • a freezer with an automatic defrost cycle that causes the milk to thaw and freeze again;
  • thawing the milk too rapidly or too slowly, especially cow milk.

Vitamin Loss. The freezing process, like many other food preservation techniques, can lower the vitamin content of the milk. The numbers aren’t staggering enough to worry about, but rather a result of the natural degradation of any food product. Although that degradation is slowed down by the freezing process, it does occur.

Off Flavors. All food products that are frozen can develop off flavors. This may be due to coming into contact with other flavors or odors of the foods surrounding your milk, if the container hasn’t been sealed properly. It could also occur because of any odors or flavors left in the vessel you froze the milk in in the first place. Finally, exposure to air during the process of freezing or moving the milk from jar to jar can cause off flavors.

How This Affects Your Cultured Dairy Products

If any of the above alterations have occurred to your milk then they may affect the flavor of your cultured dairy products. For this reason you may want to consider the following:

  • Always taste the thawed milk after it has been frozen to determine whether it will have a negative effect on your end product. If the off flavor is subtle it may go undetected in a strongly flavored ferment like kefir.
  • Consider using only fresh milk for cheesemaking. Cheesemaking tends to be a more finicky process than making other cultured dairy products. Aged cheeses, in particular, may be affected by any fat separation. You may experience a difficulty in getting your milk to produce curds properly or to age and flavor properly with previously frozen milk. For this reason you may want to reserve previously frozen milk for cultured foods like yogurt or kefir.

While freezing milk can affect the flavor, vitamin content, and texture of the milk, you should be able to use it for some cultured dairy products more successfully than others.



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