The first week of March we traveled up to our future homestead to install yet another water storage tank. While removing the forest duff where we were installing the tank, I noticed that most of the acorns still on the ground were starting to germinate!
Hmmm……… I remembered somewhere back in the recesses of my brain that when seeds germinate, the starches turn to sugar. When a brewer makes beer, he sometimes uses malted barley (which is sprouted barley) because the grain would have a higher sugar content to turn into alcohol. So, it would make sense that if I gathered sprouted acorns in the spring, they would be sweeter than the whole, just dropped acorns in the fall, and it would be easier to get the remaining tannins out of the acorn.
I did some research and found that when sprouting occurs, chemical changes naturally take place so that some enzymes convert carbohydrates into simple sugars. The complex proteins within the seed are converted into simple amino acids and most of the available fats turn into fatty acids. This makes the nutrition within the seed more readily available for digestion.
I also found this: “Germination caused a decrease in the protein, carbohydrate and starch; it increased sugar content, and had varied effects on the lipids contents of the dry samples. The anti-nutritional factor-tannin concentration was decreased.” http://www.ncbi.nlm.nih.gov/pubmed/1546053
I figured it wouldn’t hurt to try, so I gathered several pounds of the sprouting acorn nuts and brought them back to our current home in the Sacramento Valley. I decided to use the boiling water method of tannin extraction, using larger pieces of the acorn.
The first thing I noticed was that it was much easier to remove the acorn meat from it’s shell! The acorns shells had (usually) three splits at the small end, where the future root was protruding from the shell. Just a little bit of pressure on the acorn shell along one of these fissures with pliers would crack the acorn shell in half. In fact, I was able to get a lot of the acorn nut meats out of the shell whole and intact – which was nearly impossible to do with newly fallen acorns.
I decided to try boiling the acorns for 15 minutes at a time, transferring back and forth to fresh boiling water, and see how many water changes it would take to get fairly clear water – which is supposed to indicate that most of the tannin had been boiled out. Knowing that my oak is a species of red oak (I figured this out when I read that white oak acorns germinate as soon as they fall to the ground and red oaks wait until early spring) and the fact that red oak carries more tannin than white oak; I didn’t start tasting the acorns until after the fourth boiling. Ick. Then the fifth. Nope. Sixth. Maybe, but no. Seventh. Much better. I boiled for the eighth time, just to make sure. Success.
One experiment with removing the tannin from acorns that I have been toying with is using pH testing strips. Since Tannin is an acidic agent, I thought it would follow that the acorn nuts themselves would become less acidic as the tannin was leached out. So I bought some pH test strips from an aquarium supply store to check out the acidity level of the water after each boil, to see if, indeed, the acid levels dropped. I think it worked. As you can see from the picture below, the color of the water from each successive boil turned from bright yellow to orange, indicating that the level of acidity had decreased. I plan to experiment with this method using several techniques of leaching the acorns including the cold water leach method and the combination of cold water/hot water leach, along with the hot water method as above. According to my palate – the acorns didn’t taste very palatable until the pH had reached about 7, which is neutral. The eighth boiling showed a red color on the test strips (sorry, that one isn’t in the picture), which apparently was an indication that the water was no longer acidic, so I assumed no longer had any tannin. 🙂
After I had some leached acorns I had to decide what I would do with them next. Since I had leached the tannin using the hot water method, I knew that they would lend themselves to a recipe that was not flour. If you would like to make acorn flour, cold leaching is best for this because the oils have not been cooked out and the resulting cake, cookie or pastry would be less crumbly. Baked goods made from flour using hot processed acorns tends to have no structure and fall apart. So, I thought I would candy them using a recipe I have for candied walnuts!
These were pretty good! But – next time I won’t add so much cinnamon. You see, many plants contain tannin naturally, the most famous being grapes! The tannin in the grapes added to the tannin in the oak barrels is what gives red wine it’s astringent, tannin flavor. Another food stuff that includes tannin is cinnamon. When I ate an acorn after the eighth boil, I did not taste any tannin. In fact, the acorn was almost sweet. However, after roasting the acorn, I could taste just a hint of tannin. I knew that roasting acorns will tend to bring out any tannin flavor left in the acorn, which is why I boiled once more, after I no longer tasted tannin. Then, after they were candied, even through the sweet of the sugar, I could taste a stronger tannin flavor – presumably because of the cinnamon.
Will you have to boil your acorns eight times? I don’t know. Each oak tree is different. Some people only have to boil once. You never know until you try!
Will I make candied acorns again? You betcha – just not with so much cinnamon. In fact, I’m thinking of making some caramel acorn and popcorn next! Anybody want some?
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