Sauerkraut is an odd little food if you are an American. Everyone knows it is originally a German food, but it is the kind of foreign food that underlines so many differences in the way food is handled between America and Europe. In America, things are preserved through freezing and preservatives. Things are different elsewhere.
In Europe and Asia, older methods of food preservation are still widely used. In particular, pickled foods are more common in both continents than in the United States. Sauerkraut is one step further than pickled though, and it is actually fermented by the time you eat it. So, can you freeze fermented food? Do you even need to?
The easy answer is yes, you can freeze it. Not only can you, but contrary to some common belief, you should. There is a common presumption that because sauerkraut is fermented that it does not need to be frozen. The thing is that once sauerkraut is opened it has a far shorter shelf-life than before.
Freezing is not the best way to preserve sauerkraut, but it is a method that will give it a long lifespan without much upkeep. There are a lot of nuances to sauerkraut though, and you should learn them to make the most of what you have.
What Is Fermentation And Why Does It Matter?
Fermentation is interesting because it is a highly complex process that was not fully understood until thousands upon thousands of years after it was first put into practice. If that seems like an exaggeration, consider that some of the first civilizations had breweries of beer made out of fermented yeast.
Fermentation is the breakdown of a molecule in the absence of air. Many foods were once alive. Meat was obviously alive in a very recognizable way to humans, but fruits and vegetables were also alive. After they are picked from the vine, these fruits and vegetables are not alive, but they still contain living matter.
Much of a fruit or vegetable’s health benefits come from the still-living matter. One of the most important components of fruits and vegetables are “enzymes”, which humans can consume to help their bodies function better. Cooking fruits or vegetables kills enzymes, which dramatically lessens the foods’ health value.
These enzymes kind of “breathe” air. This is not exactly what happens, but they require air to function, and “breathing” is the best word in the English language for describing it. In the absence of this air though, the enzymes change. They go from consuming air to consuming other parts of themselves.
Fermentation happens when enzymes go from consuming air to consuming their own glucose. This is why aged alcohol is better than young alcohol. The less glucose there is, the less the taste of the drink is regulated by the fruit or vegetable that was fermented to make it. Though after 200 years, there are diminishing returns.
Age something for 200 years and the glucose will run out and the fermentation will just turn to spoil. This is called “200-year vinegar”, and it was discovered in what can only be described as the most disappointing experiment in human history: Monks aged the wine for hundreds of years and drank it to discover it sucked.
Fermentation And Freezing
With all this in mind, consider sauerkraut. Sauerkraut is fermented cabbage. Cabbage has the interesting property of fermenting much, much faster once exposed to air again. This is why opening a jar of sauerkraut shortens its lifespan so much. It will last for hundreds of years in a jar, but two weeks when touching air.
Once it is open though, the process of the sauerkraut rotting in the air is still a chemical reaction. That means that no matter how inevitable it is, freezing will slow it down.
If you do not know, now is a good time to learn: Chemical processes are accelerated by the heat and decelerated by the cold. Even if something is rotting, it will rot slower in the cold. To be honest, this is not exactly what is going on, but it is all you will ever need to know in the realm of cooking and food preservation.
So, to finally come around to the original question: Can you freeze sauerkraut? Yes, you can. Doing so after it has been opened will extend its lifespan by about two weeks. Because it is a fermented vegetable, it will retain much of its original texture once you thaw and/or heat it, and it will not lose much flavor.