The Brew Site

Apocalypse Beer: How to Ferment Anything

Did that catch your attention? Good! Understanding fermentation is a key component to making beer (indeed, any alcohol) but it turns out, the formula for fermentation is really pretty simple:

Water + Sugar + Yeast = Alcohol

You might think that the yeast is the biggest unknown here, but in reality wild yeasts are abundant in nature and many fruits by themselves have an abundance of yeast naturally present on them that will start fermentation with little to no effort.

No, the real unknown is the “sugar” in this equation, and thus the idea of “how to ferment anything” really means, “how to get the sugar from anything.” Once you have the sugar(s), fermentation is the easy part.

Previously we covered brewing your first batch of Apocalypse Beer and it was the most basic example of the process using three basic ingredients: water, refined white sugar, and yeast. If you have easy access to plain sugar then you have a ready supply of “fermentables” to use as a base in your beer recipes. But if you don’t have that access? Read on.

There are basically two classes of fermentables that need consideration: sugars that can be fermented directly without any processing, which includes processed sugars, syrups, honey, fruits, and so on; and sugars that are locked up in starches or complex carbohydrates which require some form of processing to extract or convert the simple(r) sugars needed by the yeast. This second class includes things like grains, roots, vegetables, and anything else that doesn’t have readily-accessible sugars.

Fortunately we have thousands of years of brewing development to guide us in converting these sources into fermentable sugars—for grain-based beverages (primarily malted barley). And, where malted barley (or wheat) isn’t available there are other strategies to be had for extracting what we need.

Let’s overview these various sources, with more detailed explanations (if needed) of how to convert or extract their sugars to follow in future posts.

(Note: I am not covering the fermentation of meat or other similar proteins. This is an entirely different beast, so to speak, and as far as I know there’s no history or tradition of brewing fermented meat beverages.)

“Simple” Sugars (No conversion required)

These are fermentables that are already in ready-to-ferment sugar form that the yeast will be able to convert into alcohol easily. Many of these you may be able to find from a scavengeable source; others occur naturally. Very easy to ferment: just add water and yeast.

Tree Sap

Of course if you are familiar with maple syrup then you probably realize that this comes from concentrating the sap of the maple tree, which is obtained by drilling a small hole in the trunk of the tree and collecting the clear sap that runs out of it. Maple trees are the most common tree to collect sap from, and they typically have a sap sugar content of around 2% on average—which means there is a need to concentrate the raw sap down to syrup form, which can often be at least a 40-to-1 ratio. In other words, you need to boil 40 gallons of sap down to get 1 gallon of syrup.

If there are few or no maple trees where you are, there are fortunately other trees besides maple which yield usable sap: birch, sycamore, walnut, larch, and lime. That list plus several techniques for tapping a tree to get at its sap can be found here, one of which may work well for post-apocalyptic sugar hunters: cutting or breaking off the ends of small branches and collecting the sap in plastic bottles.


It almost goes without saying that fruits are full of fermentable sugars that you easily use: chop or mash them up and use them directly in your wort, no further processing is necessary (besides peeling and pitting, etc.). Of course different fruits have different (average) concentrations of sugar; here’s a sampling:

More here. Bear in mind, the fruits don’t have to be fresh: if you can scavenge canned fruit, that will work just fine (as will the syrup the fruit is canned in!).

Juniper Berries

While technically a fruit, juniper berries rate a special mention because besides being used for flavoring gin, I suspect most people would be surprised to find out that juniper berries in fact have a high percentage of dextrose sugar—up to 30%! Stephen Harrod Buhner in Sacred and Herbal Healing Beers writes:

The presence of such a large amount of dextrose may account, in part, for the use of juniper and juniper berries as an integral part of Norwegian brewing… juniper beer was sometimes made with juniper, water, and yeast only—no other source of sugar being used.


Beets are a root vegetable but they get special mention here (as well as in the next section) because they are naturally so full of fermentable sugars already that you can cook them down to extract the juice and use that directly in your brewing as you would any other fruit juice or syrup. Beets are in fact so sugar-rich that a large percentage of refined white sugar comes from them!

Packaged Foods

In the course of your scavenging and salvaging, former grocery stores and other markets may provide some valuable source of brewing fermentables—provided they haven’t been completely looted. Many packaged foods are full of sugar you can brew with (provided you aren’t eating them instead!), such as:

Fermentables that require “unlocking” (converting from starches)

Sugars that are locked up in starches, such as those found in most grains and vegetables, require enzymatic conversion to transform those starches into sugars. (The science behind this is because large starch molecules are really lots of smaller sugar molecules all strung together, and particular types of enzymes called amylases can break these down into those individual sugars.) You might be wondering where you might find the amylase enzymes needed to transform these materials into fermentable sugars—after all, this sounds very industrial and scientific and since society has collapsed, surely this isn’t possible, right?

Wrong! Two of the main grains used in the production of beer develop the enzymes naturally. You just need to know how to make use of them.

(Actually amylase enzyme is available commercially but I have no idea how easy it will be to find in a post-apocalyptic setting. Of course you could raid your local homebrew supply store before the looters get there any take any and all enzyme you can find…)

Grains: Barley and Wheat

These are the two (traditional) staple grains used in brewing and the primary source of fermentables in beer. Of course the grains themselves aren’t simply thrown into a kettle of water and cooked: you’ll get hot cereal. Instead there is a two-stage process required to extract the enzymes and then the sugars from them.

  1. Malting: The raw grains are first germinated, or sprouted, by soaking in water and then keeping moist; this causes the grain to start producing the necessary enzymes that will be needed in the later steps. Once the grains have sprouted just enough (typically the sprouted part, or “acrospire,” is as long as the grain itself, if not a little shorter), the process is stopped by drying or kilning the grain. There is a good (if a bit technical) article on malting here that will get you started. The resulting malted grains should have the proper levels of enzymes that will convert their starches to sugars during the next stage (mashing).
  2. Mashing: The malted grain is crushed and soaked in hot water (150°F is a good target) for at least one hour, then the resulting liquid is rinsed into the brew kettle and boiled. What’s happening is the hot water has activated the enzymes formed during malting, and they are converting the grain starches into sugars—giving us the fermentables we need to make beer.

It gets better: barley and wheat have a special place in brewing because they already naturally have enough enzymes to perform the starch-to-sugar conversion, while other grains may not; and in fact, these malts are usually also able to convert the starches from other types of grains—and other starchy sources, too—up to a point. This will prove incredibly useful when you are working with the following materials which may otherwise be inaccessible to you for brewing.

Grains: Other

Any variety of grain can be combined with malted barley and/or malted wheat in the mash (hot water bath) to take advantage of the enzymes present in the malt to convert the various starches to sugars: rye, oats, rice, corn, sorghum, millet, quinoa, amaranth, and so on. Many of these grains need to be cooked in boiling water prior to being added to the mash to gelatinize them, which makes them open up their starches to the conversion process.

There are also several grains that, like barley and wheat, can be malted to develop the amylase enzymes that will allow them to convert their starches to sugars without help: oats, rye, and sorghum all have high enough diastatic power to do this. (“Diastatic power” is the measure of how much starch-converting enzymes a grain may contain. The higher the diastatic power, the more it can break starches down to sugars.)

Rice (and an alternative to malting and mashing)

Rice deserves a special mention in this section because of both its long use in Asian fermented beverages like chang and sake, and the fact that it cannot be malted—which means that rice doesn’t contain the amylase enzymes that malting develops to ultimately ferment it. When used with malted barley or wheat it needs to be cooked and mashed like other grains; but in sake brewing, there are no other grains, malted or otherwise. So the question arises: just how are the starches in rice (by itself) converted to fermentable sugars?

The answer is “mold” and it provides a second, interesting avenue to explore for processing grains. The rice in sake and chang brewing is fermented by the addition of special yeast cakes containing fungi, primarily Aspergillus oryzae, which do the work to convert all the available starches to sugars which the yeast in the cake subsequently ferment. In the making of sake the addition of special Aspergillus-infected rice, called koji, does this work. And there’s no reason this special mold couldn’t be added to any other cooked grain to work its conversion magic.

Now obviously you can’t just pop into your local Asian market in the post-apocalyptic world and pick up a yeast cake or koji to prepare your grains and brew your beer; so what to do? Fortunately there is a natural source of Aspergillus fungi which you can use here: ginger root. Here’s Buhner again:

The simple addition of crushed gingerroot to any cooked starchy grain will result in starch conversion and the subsequent growth of Saccharomyces yeast  and the beginning of fermentation.

This will be a slower process—days rather than hours for mashing (though this evens out more if you count time for malting)—but it should be no less viable.

Sweet Potatoes

Sweet potatoes rate a special mention as not only do they already have a naturally high sugar content, but they also have enough natural amylase enzymes and diastatic power to convert their own starches without using barley (or wheat), making an all-sweet potato beer a possibility. For this to work it may required raw sweet potatoes—canned sweet potatoes have likely undergone the high-heat cooking/pasteurization/sterilization of the canning process which would denature (destroy) the amylase enzymes needed for self-conversion. (You could still add canned sweet potato to a grain mash to convert the gelatinized starches to sugars though.)

Two good sources (with additional links) to read up on this process are here and here, but the basic process should be:

The resulting should be about 2 gallons of wort full of sweet potato sugars, and fermentable.


Beets were mentioned in the “simple sugar” section above for a very good reason—they are already full of fermentable sugars! You can cook beets down to extract the juice and use that juice directly in the beer brewing, no conversion process required. (You could still mash them with your malted grains, if you like.)


Other types of vegetables fall (roughly) into three categories: 1) starchy (often root) vegetables like potatoes, turnips, and parsnips which need to be cooked and mashed along with malt in order to extract their sugars; 2) vegetables that contain sugars (but little to no starch) that can be used directly in the beer without additional processing; and 3) vegetables that contain little of either starches or sugars but may be high in fiber like lettuce, celery, and mushrooms (though those are technically fungi). Some examples of each of these categories are:

  1. Potatoes, broccoli, cauliflower, turnips, parsnips, beans, peas, corn (as a grain of course), sweet potato (also see above), squash, pumpkin — processing the starches is required, whether mashing with malted grains or using Aspergillus fungi. These should all be fully cooked before using.
  2. Carrots, bell peppers, sweet potato (also see above), onions, beets (also see above) — these can be added directly to the beer while brewing, cooked or raw, and should be chopped or mashed finely to maximize the sugar extraction.
  3. Lettuce, celery, radishes, mushrooms, green onions, cucumber, many greens — these would be better suited as flavor components.

It’s important to note that unless you have a supply of fresh vegetables (perhaps you’re growing your own, or finding wild veggies—or even raiding others’ gardens?) you may be relying on what canned vegetables you are able to salvage from abandoned markets and stores.

Orchid Roots

Did you know orchids are edible? Indeed they are, and in particular the roots are nutrient-rich starchy tubers—very much like potatoes or parsnips. As such, you should be able to process these in the same type of way: boil them until they are soft (to gelatinize the starches), chop finely or (better) mash them up, and add them to your mash with barley or wheat to covert the available starches to sugars. Orchid beer, anyone?

Packaged Foods

As in the previous section, you may run across old groceries and markets that may be scavengeable for brewing fermentables. In the previous section we covered packaged foods containing sugar; here are some examples of foods you’ll have to process in one of the ways described above to get the sugars out of them:


Nuts actually don’t provide much in the way of fermentables, as they are largely made up of protein and fat in the form of oils. So while you can’t ferment nuts directly, you can still add them to your beer where they will add a flavor contribution. Be aware though that with too many nuts, the oils can affect flavor and head retention (if that’s something you’re looking for).

Have I missed anything?

This article covers a lot of ground and should help give you the tools you need to figure out how to ferment many foodstuffs you’ll likely come across. But if I’ve missed anything or there are further ideas, leave a comment below or contact me directly, and I can round up the suggestions in a future post. And I’ll post additional eclectic sources and ideas for brewing fermentables as I come across them as well—Buhner’s book alone is chock full of good ideas!