Malting Acorn for brewing
Humans have been consuming alcohol since long before we started practicing agriculture and harvesting grains. Acorn beer is a bit of a throwback to those early days of brewing, but can benefit from modern techniques. If you’re interested in the history, check out this excellent article from Brewer’s Almanac (pdf).
Acorn has high starch content and a composition far closer to grain than to most other nuts, which makes it ideal for brewing. Leached acorn grinds can be used as a replacement for barley and other grains. The key limitation is that they also contain the enzyme polyphenol oxidase, which gives any beer brewed with acorn a dark color.
Process:
The first step is to age your acorns before using them. Clean them as described in our articles on harvesting, and then let them age in their shells for at least three months someplace cool and dark. This will ensure they are fully ripe and that there is enough sugar available for fermentation.
Soak the nuts for several hours, discard any floaters, and pour off the water.
Leave the nuts someplace cool (65F or lower) and dark until they begin to sprout. At a sprout of less than one inch, shell and grind the nuts.
Proceed with cold leaching as normal and then grind to a rough meal - not a powder or flour. It’s important that you use cold leaching because otherwise you will lose too much of the starch that you need to ferment.
You can then substitute malted Acorn grinds at a 1:1 ratio for all or some of the grain in your favorite dark beer recipe. It works particularly well in dark Oktoberfest-style beers, and produces a final brew with notes of bourbon thanks to residual tannins. You may want to use the last water from your leaching process in your beer to get more of that flavor.
If you prefer to use a more conventional malt, you can still use leached acorn grinds as a replacement for the unmalted grain used in many recipes.
Note: Some brewers also use small amounts of un-leached acorn in beer or mead to give a stronger tannin flavor, similar to what you might achieve with oak barrel aging or by adding wood chips. There are also accounts of people fermenting the nuts either alone or with salt as a way to break down tannins without leaching, and then using those pre-fermented nuts in brewing. More research is needed to validate that these methods are safe.
