The most important thing when hot rinsing is to keep an eye on the temperature. In the literature, it is often stated that the acorn is "cooked" during hot leaching, but actually they are meant to be boiled, thus heated to 85–96°C. If they are cooked, the starch in the acorns begins to convert in a process called gelatinization. What then happens is that some of the tannins are permanently bound to the starch molecules. The end product can still be eaten, but will taste bitter. To keep track of the temperature, I use an analog thermometer, digital ones have a tendency to shut off after a while. When I see the temperature starting to approach 95°C, I usually pour in a couple of deciliters of cold water to bring the temperature down again. It has proven to be the easiest way to keep the temperature within the desired range. If you want to leach out large quantities often, it may be worth investing in a so-called electric boiler (available for beer brewing) which can keep the temperature for you so you don't have to stand by the stove all day.
- Peel the acorns and divide them into two halves.
- Place them in a pan of water. Use the least 5 liters of water for 1 kg of acorns. With smaller amounts of acorns, relatively more water is needed to reduce the risk of overheating.
- Heat the water to 85-96°C. Make sure the water never boils!
- Taste the acorns after approx 5 hours. If the bitterness is gone, they are ready, otherwise a little more time is needed. Drain the acorns when you think they are fully leached and wash them in cold water.
Now you can dry the acorns as they are to use them in stews, to steaks or similar. The drying time in an oven or dryer is 12–24 hours at a maximum of 65°C. You can also crush the moist acorns using a mortar and pestle or run them through a meat grinder. Then you will get a nice mass that can be used immediately or dried for later use. The pulp takes 6–12 hours to dry in an oven or dryer at a maximum of 65°C.
This post is an edited excerpt from the award-winning book “Nut grower's manual” by Philip Weiss (2022).