There are several different approaches to getting the tannins out of the acorn using cold water. Decisive here is to crush the acorns relatively fine, so that the surface that the water can come into contact with is large. The peeled acorns are crushed using a powerful mixer, a mortar or a meat grinder. I recommend five different methods of cold leaching:
The jar method: This method is quite labor intensive, but allows you to access the starch in the acorn in an easy way. Do this:
- Fill a large glass jar one-third full with crushed acorns.
- Top up with water and shake. Put the jar in the fridge. At room temperature, the acorns start to ferment.
- Change the water once a day. When you pour off the leachate, you will see a whitish scum forming, some viscous liquid that floats on the crushed acorns. It is the starch that should remain, so do not pour off too much liquid during the water changes.
- Taste the acorns when the leachate becomes clear and less cloudy. They are ready when the bitterness has disappeared.
- Pour off most of the leachate when you think the acorns are ready. Pour the rest of the contents of the jar into a clean towel that you place over a bowl. Squirt the liquid into the bowl to collect the starch. Wait until the starch has settled before pouring off the excess water. Then the starch is ready to use, for example to make acorn tofu
The urlakade, you can use the crushed acorns directly or dry them for later use. Dry them in an oven or dryer at a maximum of 65°C. It takes 6-12 hours. The acorns can then be frozen or stored in glass jars with tight-fitting lids. In glass jars, the shelf life is about one year.
Cold-lacquered acorns are slightly better to use in baked goods than hot-lacquered acorns. You can replace at least half of the regular flour with acorn flour in baked goods that do not need to rise (for example pancakes, flat bread and waffles) and get good results. In breads to rise, the limit seems to be about a quarter to get comparable results as with regular flour.
Hink methods: If you have a lot of acorns to leach out, you can use buckets instead of glass jars. Feel free to put a cloth bag in the bucket to get the crushed acorns out more easily. Instead of using the refrigerator, you can put the bucket outside or in a cold room, so that the mixture does not start to ferment. Otherwise, the procedure is the same as with the jar method.
The drop method: Just like dripping, boiling water can dissolve the tasty substances from ground coffee in a coffee machine can drip, cold water dissolve the tannins from crushed acorns. The easiest way is to put a clean kitchen towel in a colander, fill it with the crushed acorns and soak the whole thoroughly so that the mixture becomes saturated with water. Then you set the water faucet so that it drips at the right rate. After as little as 12-24 hours, the acorns are leached and ready to use. The disadvantage of this method is that it is not possible to find out the starch in the same way as with the can method.
The stream method: Are you clean?, running water at hand, you can do as many of the acorn-eating people did and hang cloth sacks of crushed acorns in the running water. The process takes anywhere from a few days to a couple of weeks. You need to taste the acorns periodically to see if they are done. Don't make the mistake I did in the beginning and hang the acorn in a stream that brings a lot of sediment and humus. After two weeks, the bitterness was certainly gone, but it had been replaced by a pervading taste of dy which I could not get rid of even with vinegar. I have therefore switched to leaching the acorns in a cold spring near the house. I use small polyester bags that you store vegetables in for this purpose. They are coarse enough to let a lot of water through, but fine enough so that acorn crush does not leak out. Just like with the drip method, it is not possible to take advantage of the starch with the stream method.
The toilet method: You who use a flush toilet can use its cistern (and no other!) to get the same effect as the cold source, that is, a continuous flow of fresh water that washes away the tannins. Every time you flush, the water will be renewed, which means that you avoid the eternal water changes of the jar method, which are easy to forget. When the rinse water is completely clean, you can assume that the tannins have been leached out.
This post is an edited excerpt from the award-winning book “Nut grower's manual” by Philip Weiss (2022).