Types of Fermentation: Lactic, Alcoholic, and Acetic Explained
Nov 28 | Written By Allie Faden
Alright, we’ve decided to repost this as a reminder post, because people have had questions, and a lot of them, that relate to not understanding the different types of fermentation. Understanding those differences really helps answer a lot of secondary questions about how and why to do certain things to make your ferments, as well as sometimes helping people understand what’s gone wrong in a given process!
Did you guys know there’s more than one kind of fermentation? There are a bunch, really, but most people engage with one of three types of fermentation in their food prep: lactic-acid, ethanol, and acetic acid styles of fermentation. They all do a little something different, and in some cases you see multiple processes within the same product!
What is fermentation, anyway?
Fermentation is a metabolic process. During fermentation, carbohydrates are consumed by the relevant yeast and bacteria for its specific process and converted over into acid or alcohol. And that’s really all it is! From a practical standpoint, fermentation is a series of methods to forestall decomposition/rotting of a food product. It doesn’t stop the food product from going bad, but rather slows it way down while adding additional nutritional benefits. Beyond food production, fermentation is also used in some industrial processes, such as the production of hydrogen gas, sewage treatment, and production of biofuels.
There are 3 main types of fermentation (and several others, beside): lactic acid fermentation, ethanol fermentation, and hydrogen and methane gas production. We’re only going to worry about the first two types here, since gas production fermentation isn’t particularly relevant to what we want to eat on a given day. Some sources will also list acetic acid fermentation as another type, but I would argue that it belongs as a sub-category to ethanol fermentation. Accordingly, it’ll come after we talk about ethanol fermentation.
Lactic acid fermentation at its most famous - kraut!
The Matter of Food/Getty
Lactate Fermentation
This is generally what people are talking about when they’re talking fermentation. Sauerkrauts, yogurts, sourdoughs, all sorts of food products fall into this category! These are the staple ferments, as it were. Lacto-fermentation is essentially defined as fermentation that occurs primarily due to the presence and deliberate yet controlled growth of Lactobacillus acidophilus, Lactobacillus ssp., or Lactococcus ssp. Keep in mind that most lacto-fermented products will have other microbes, and this generally will be true of all ferments that there are more microbes than just the ones primarily responsible for the process in question.
It’s also a thing we do in our bodies when our muscles can’t get enough oxygen, and this is really what results in those charlie horses you get in your legs, feet, and sometimes other places.
Lactic acid fermentation is always anaerobic. This is why we tell you that you can use your lids on kefirs and such, though I personally find the avoidance of gnats to be the reason everyone should use lids on these bad boys.
This will better explain the process to those of you interested in the science.
I was really stressed out over this image, because I lost the source. It took me hours to track it down again so I could remove the dagger from my academic heart!!
Some stuff that’s lacto-fermented
Sourdough
Yogurt
Milk Kefir
Cheese
Sour Cream
Acetone
Methyl alcohol (the stuff in the recalled hand sanitizers that can kill you)
Kvass
Tofu
Some antibiotics and vitamins
Hákarl
Fermented pickles/other vegetables
Many fermented fruits
Miso
Nattō
Various fish sauces
Brem
Preserved meats (whey and other forms of fermented meats)
Cocoa/chocolate
Various spice pastes
Soy Sauce and Tamari
Tabasco (theirs is fermented 3 years on average, sometimes 5) and other various hot sauces
Cod liver oil (not all preparations, but definitely traditional ones)
Salami
Ketchup
And a lot more. I put it in this long list format so you could visually appreciate the scope of how much stuff is lacto-fermented. It’s soooo much! I think this is probably enough on lacto-fermentation, though, since this is the main thing most of us are up to in our kitchens and we pretty much understand what’s what with that!
We’re obviously moving onto the boozy portion of our little journey now. Logan Weaver/Getty.
Alcoholic Fermentation
Right out of the gate, let’s clear this up: kombucha (and jun) is alcoholic, not lacto, fermentation. Ditto water kefir, even though these guys do really contain bacteria that would make you think they’re lacto-fermented. There’s a lot of confusion about this but kombucha’s the ferment this is the ferment to use if you want to make booze from a ferment you already like in its more normal form rather than brewing in the more usual fashions.
Our list here is pretty short: booze in general, kombucha, baker’s yeast (the commercial kind), water kefir, biofuel. Due to the Pasteur Effect, there’s some weird stuff going on with making drinkable alcohol. Most alcoholic fermentation occurs due to Saccharomyces cerevisiae or other Saccharomyces yeasts. We call this aerobic fermentation most of the time, but it’s a bit more complicated than that. You need an aerobic environment to encourage the relevant yeast (and some bacteria) growth, but you actually need an anaerobic environment for the alcohol production itself.
What is most important to know here, other than the principle yeast responsible for it all happening, is that alcoholic fermentation is a two-step process that largely varies based on the coenzyme at play in the moment.
Enzymes in question.
As an example, when I make mead or ale, I do have a period in which I am stirring the brew to get air into it, usually lasting up to a full month in the case of mead. Once it’s all bubbly and ready to eat that honey, though? Straight into something airtight, and normally with an airlock.
I only skip the airlock in my ales and beers if I’m making a short brew with a relatively low ABV. By “relatively low,” I mean it’s fine for kids to drink. So not very alcoholic at all! The ABV in those short brews generally will top at around 2%, the same amount well-fermented kombucha can have. In those cases, I just use a cork instead of the airlock because I’m looking for something light and refreshing rather than boozy. Basically the ale or beer equivalent of kombucha, if you will, and generally with pine and fruity flavors so they’re more fun. Or maybe it’s just me they’re more fun for? I don’t know. Outside a couple of shots of bourbon per year, I don’t usually drink anything alcoholic enough to get me drunk if I really like the flavor of it and want to drink a couple of glasses of it. Beers and similar like this are often called “small beers.”
I don’t ever skip the airlock in my meads, because they can take years before they’re ready to bottle. Too much can happen to them during that time otherwise, and I’ve had to pitch a 5-gallon carboy of show mead specifically because various children’s hands opted to remove the airlock while I wasn’t paying attention. I was heartbroken, as you’d expect.
Both of the recipes in the following video are good. I’ve made them, and variations of them. In place of the barm, I use sourdough starter. I then save the yeast from the small beer and use it to make bread. Stupid tall loaves with that recycled sourdough!
What alcoholic fermentation actually is is the conversion of carbohydrates in the raw ingredients to alcohol instead of to acid.
One quick note: some of you have asked about making booze from water kefir, and while I’ve given my recommendations without having actually tried to do it, I did find a recipe that made it to 3%. Here it is!
This brings us to the weird and wonderful acetic fermentation!
DANG IT! I was so happy that I found that other source that I forgot the name of the person who did this picture. Franz _________/Getty. Someone fill in the last page, please, if you recognize it. This is insanely embarrassing.
This is where, for me, it gets really cool, although it’s very short and simple to explain within the larger context of the above. I also am one of those weirdos who likes to drink vinegar plain, so there’s that. To have acetic acid, you have to have some kind of acetic acid bacteria (AAB) in the mix. This typically will take a different form, depending on the product you’re making. AAB are involved in the process for kombucha, vinegar, water kefir, lambic beers, and nata de coco. Whichever of these little guys you find will still be in the Acetobacteraceae family, so that really does streamline things a bit. Here’s another chart that tells you more!
This chart is awesome and very informative!
The simplest explanation of acetic acid fermentation is the culture oxidizes sugar and/or ethanol to make acetic acid (vinegar). This is why some of you are able to keep your kombucha just to make vinegar with, why you can make your own vinegar from fruit scraps, and why no one who’s actually trying to brew cider, beer, or wine is excited to see a SCOBY in there. That SCOBY means you’re about to get cider, malt, or wine vinegar! Great to cook with and for other things, but probably not what you were shooting for if you’re were planning for a party.
Since this pretty much wraps up everything I have to say, so I’m going to leave off with a video teaching us how to make homemade nata de coco!
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