Sauerkraut gets its distinctive sour flavor from lactic acid that forms when the natural sugars in the cabbage are fermented. It’s pretty easy to make this happen at home, so get some cabbage and try it! See Step 1 below to get started.
Ingredients: One head of cabbage (as fresh as possible). Salt. The added iodine in common table salt will interfere with the microorganisms, so instead use sea salt or pickling ("canning") salt, which has no added iodine or anti-caking agents.
Shred the cabbage: Remove any outer leaves that are brown or damaged. DON'T wash the cabbage -- you'll want the natural bacteria on the leaves. They're what causes the fermentation to occur that turns cabbage into sauerkraut. Weigh the cabbage head. You can do this at the store before bringing it home, since many supermarkets have scales. Cut the head into quarters, so that the core (stem) is cut into quarters. De-core by slicing away the thick stem. With the quarter-head on a cutting board, carefully slice the cabbage into shreds about the thickness of a dime. Some people shred them more thickly, though (about a quarter inch).
Put the cabbage shreds in a glass or ceramic crock.
Sprinkle the salt onto the shreds. You should add about 3 tablespoons per 5 pounds of cabbage. This translates into 1.8 teaspoons per pound. If you're concerned about saltiness, start with 1 teaspoon per pound and add more until it reaches a good level to taste. The salt serves multiples purposes. It pulls water from the cabbage, hardens pectins for better crunchiness, and discourages the growth of bacteria other than lactobacilli so the sauerkraut can be stored for longer periods of time.
Massage and squeeze the cabbage with your hands. This is to break down cell walls and encourage the release of water. Continue until the cabbage feels very wet.
Push down the shreds and see how much liquid there is. If you can't compact the shreds below the level of the liquid, add some salt water: Dissolve 1 tablespoon of non-iodized salt in a cup of water, and add it to the cabbage shreds.
Cover the whole container with a towel to keep dust and other things out of the container. Alternatively, transfer the cabbage and its liquid to a jar. Try to make sure all the cabbage is completely submerged.
Let it ferment. Put it in a cool place and wait about 4-6 weeks. 60 to 70 degrees F will speed up the process but cooler temps may produce better flavor. Try the sauerkraut once a week until it reaches the flavor you're looking for. If it's in a jar, keep an eye on it and unscrew the lid periodically to let air escape. Don't worry if some mold grows around the edges of the container. It won't get far. Just remove it when you see it.
Eat and enjoy! If you don't eat it all in one sitting, put it in the refrigerator to pause the fermentation process.