Fermentation 101: An In-Depth Beginner’s Guide to Fermenting Foods at Home

sauerkraut and peppers fermenting in jars

While fermentation has exploded in popularity among foodies recently, it’s an ancient practice that dates back to 7000 BC. Various cultures have embraced fermentation in different ways, coming up with favorites from sauerkraut and kimchi to beer and wine. If you’ve been itching to ferment, but don’t know exactly how to get started, you’re in the right place. I’ll cover all the great reasons to ferment foods, what you can make, the science behind fermentation, equipment you’ll need, and how you can get started by lacto-fermenting any vegetable at home right now!

Why Should You Ferment?

If fermentation is an ancient technique, is it really worth doing in today’s age of convenience? I hope to convince you it is, here are some reasons why:

It Preserves Food

Are you a gardener, or just prone to overspending at the farmers’ market? Fermented foods can easily last months, saving you money and cutting down on waste.

It’s Fun and Easy

If you like experimenting with new recipes and techniques in the kitchen, you’ll have a lot of fun with fermentation. It’s half science, half cooking, and a little bit of magic. Also, there’s not a ton of active time required. Once you get the hang of it, you’ll be able to get veggies fermenting in just a few minutes.

It Improves Immune Function and Adds Probiotics

Eating fermented foods add probiotics, digestive enzymes, and healthy acids to your body. It also helps to increase your immune function and overall digestive system health.

It Tastes Amazing!

Fermented foods and drinks have a unique taste that people really seem to be embracing lately. It’s funky, salty, sour, and delicious. There’s also an element of unpredictability – you never know exactly how something will turn out until you’ve tried it, and you can come up with all sorts of concoctions through different flavor combinations. Yum!

What Kinds of Foods Can You Make with Fermentation?

sauerkraut close-up from above jar

The short answer: you can ferment just about anything. As far as historically established recipes, sauerkraut is a classic, and it’s a great recipe for beginner fermenters (all you need is salt and cabbage). For a spicier, Asian take on cabbage, try some kimchi.

If you’ve dabbled in baking bread, you probably know that sourdough comes from a fermented starter. However, you’re not just limited to classic boules. Sourdough starter is a natural leavening agent that works just like dry yeast, so you can make sourdough croissants or sourdough pizza.

Also note that anything with a tangy flavor from vinegar can be achieved through fermentation, with more beneficial bacteria. For example, you can make fermented hot sauce or pickles.

There’s also yogurt, tempeh, kimchi, miso, and dozens of other foods that are made through fermentation.

Lastly, don’t forget beer and wine, but there’s a whole world of fermented beverages beyond those. Kombucha, tepache, kefir, and beet kvass are a few to try if you haven’t before.

How Fermentation Works

You might wonder how fresh vegetables turn into fermented food with a bit of salt and water. Let’s talk science for a second!

Vegetables naturally contain mold, yeast, and bacteria. Over time, these are what cause the fresh broccoli in your refrigerator to spoil. Some of those bacteria, yeast, and mold play a considerable part in the fermentation process, but they’re only in small numbers compared to the ones that will spoil everything.

When you add salt to food and limit contact with oxygen, it creates an environment that makes it impossible for mold and harmful bacteria to live, while allowing the beneficial microbes to flourish.

During this process, the yeast starts to break down the vegetables, turning them into acid, carbon dioxide gas, and other compounds. That acid is what gives fermented food tart, tangy flavors, in addition to protecting against harmful bacteria.

3 Types of Fermentation

There are three different types of fermentation. Let’s take a look at each one.

Lactic Acid Fermentation

Lactic acid fermentation, also known as lacto-fermentation, is the most common way to ferment food. “Lacto” is short for Lactobacillus, which is a common bacteria all around us. It’s in the air and on the surface of plants, fruits, and more.

lacto-fermenting peppers and onions for hot sauce

During the process of lacto-fermentation, these bacteria eat sugar in the food and turn it into lactic acid. As outlined above, lactic acid is a natural preservative that also adds distinctive flavor.

Examples of lactic acid fermented foods include pickles, kimchi, yogurt, and sauerkraut.

Ethanol (Alcohol) Fermentation

During this process, yeast breaks down the molecules in starches or sugar, turning them into alcohol. This process creates wine and beer.

Acetic Acid Fermentation

Examples of acetic acid ferments include apple cider vinegar and kombucha. During acetic acid fermenting, starches and sugars from fruits or grains ferment, turning into drinks, vinegar, or condiments.

Equipment Needed for Fermentation

In addition to whatever food you want to ferment, you’ll just need a few items to get started.

Vessel

The first thing that you need is a vessel to hold the food. Don’t use anything that is plastic, metal, or not food-grade. That means stay away from stainless steel.

Instead, look for a vessel that is wood, glass, or ceramic, but be sure you pick something that uses a lead-free glaze. Crocks are a classic choice and have been used for decades, but they can be pricey.

The most practical choice are canning jars or old spaghetti jars you have around. You can finally use those jars for something!

Fermentation Weight or Airlock

fermentation airlock

You need to make sure whatever you’re fermenting isn’t exposed to air, and there are a few ways to achieve this. Pictured above is an airlock, which uses a small amount of liquid to ensure that gas buildup can escape, but nothing can get inside. Fermentation weights are another option, and they work by keeping food submerged under water. While there are weights specially designed for fermentation, you can use anything that fits nicely in your vessel, like a ramekin.

If you don’t want to buy an airlock or have anything that works as a weight, I’ll show you how to keep your veggies safe with a sandwich bag full of water below.

Digital Scale

You’ll need a scale to calculate how much salt your projects need. With fermentation, salt is key to creating a safe environment where the right bacteria can flourish. Since we are talking about your health, the precision of a digital scale is definitely worth it. They are easy to find online or in stores like Bed, Bath, and Beyond.

Salt

Almost all fermented recipes call for salt, and you need a good quality, chemical-free salt. Don’t use iodized salt or table salt, which contain substances that might kill the good bacteria.

What can you use instead? Here are a few choices:

  • Pickling Salt
  • Kosher Salt
  • Real Salt
  • Celtic Sea Salt
  • Himalayan Salt

Creating the Right Environment

This is something fundamental to understand about fermenting foods. You need to have an oxygen-free environment, and as you learn how to ferment, you’ll see the term anaerobic, which means “in the absence of oxygen.”

An anaerobic environment is essential because the lactic acid we are developing in our vessels thrives in a low or no oxygen environment. When you expose your ferments to oxygen, it stops the growth of the good bacteria, leaving it vulnerable to mold. You create this environment by using airlocks and having airtight vessels, as mentioned above.

Aside from keeping oxygen out of your ferments, you need to keep everything at an ideal temperature. Veggies ferment best at 68-72° F, but milk ferments handle temperatures up to 90° F.

How to Ferment Any Vegetable With Lacto-Fermentation

Are you ready to start fermenting? All you need is one vegetable. Try to go for something organic or use a veggie from your garden. We don’t want any chemicals interfering with the fermentation process. And obviously don’t use anything that’s bordering on going bad or has major blemishes.

I promise once you go through this process a couple times, it becomes second nature, and you won’t even have to think about the individual steps or calculations. Just bear with me if it seems a little tedious the first time through.

Step 1: Prepare Your Scale and Vessel

empty glass jar on digital scale

Here’s where your scale comes into play. Turn it on and set the units to grams. Place your empty vessel on your scale and zero it out.

Step 2: Add Veggies and Water

glass jar full of cauliflower and water on digital scale

Next, add your vegetables, and then enough water to cover them. We are only interested in the weight of the veggies and water combined, so don’t worry about how much the veggies weigh alone.

Step 3: Calculate How Much Salt You Need

phone calculator next to scale and jar

Now it’s time to calculate how much salt is needed to keep your fermentation safe. Typically you’ll want between two and three percent, so multiplying your weight by .025 is a pretty safe bet. Peppers are an example of a vegetable that’s prone to mold, so you’ll want to be in the 3%-5% range. If you’re making fermented pickles from cucumbers, 5% is often recommended. But for the majority of harder veggies that aren’t super high in moisture content, 2.5% does the trick.

Step 4: Weigh Out Your Salt

salt in bowl on digital scale

Now grab a bowl and weigh out the salt that you calculated in grams.

Step 5: Add Water to Salt and Mix

saltwater in bowl on digital scale

Next pour the water from your jar into your salt, and mix the salt until it dissolves.

Step 6: Add Saltwater Mixture Back to Original Vessel

fresh cauliflower fermentation

Now just add that saltwater back to your jar. I know it might seem like we are going in circles taking out water and adding it back in, but this way we know the exact amount of water through the entire process. Mixing the salt separately also ensures that it is evenly evenly distributed and fully dissolved.

Step 7: Submerge Your Veggies

fermentation weight made from water in plastic sandwich bag

Yes, that is a sandwich bag on top of the cauliflower in the last photo. Specifically, it’s a sandwich bag full of water. If you don’t have fermentation weights or an airlock, this is a great way to keep your vegetables under water. You might be wondering why an airtight lid is a no-go, and that’s because gas needs to escape. Your jar can and will explode if you don’t let air escape.

Step 8: Keep at Room Temperature and Taste

cauliflower fermenting next to sauerkraut

Now just find any room temperature space that doesn’t get direct sunlight, and you’re officially fermenting! Check on your ferment around day 3. You can taste it and decide if you like the flavor. If you don’t, wait another day or two and taste again. Continue this until it has developed a flavor that you enjoy.

Step 9: Put in Cool Storage

Once you’re satisfied with the flavor, it’s time for cold storage. You want to store it somewhere that is consistently below 55℉. The colder it is, the longer your ferment will hold the same flavor.

For many people, the best place is the refrigerator, but you can use a cellar, a chilly basement, or somewhere else that is always cold.

Problems and Frequently Asked Questions

Problems can be intimidating to newbies, but most of the time there’s really no reason to fret. Worst case scenario, you will have to throw out some veggies, so try not to stress too much. Let’s do some troubleshooting!

On Mold and Kahm Yeast

All fermenters will, at some point, encounter mold, but there is a difference between mold and Kahm yeast. You have to learn the difference.

Kahm yeast (pictured above) is a white film that covers the top of your fermented foods, and it can be hard to distinguish from mold. The good thing is that Kahm yeast doesn’t harm your ferment at all. Instead, it’s an aerobic yeast that forms when the sugar is used up and the pH level in the ferment food drops.

You can tell the difference because mold is more raised and fuzzy, and it can be white, black, pink, blue, or green. Typically, mold starts as spots on the surface and gradually spreads into a thicker layer.

White mold is harmless, and all you need to do is scrape it off of the top. Unfortunately, if you find any other mold with a different color, you have to toss it all out.

My Brine Got Cloudy – Is It Okay?

cloudy fermentation

Yes, cloudiness is common with lacto-ferments, just like in the photo above. In fact, it’s a good sign of the bacteria doing their thing.

Is It Normal for My Brine to Bubble or Foam?

Yes, absolutely! Some veggies create more foam, while others have none at all. The foam tends to come from vegetables with higher sugar content, like carrots. Foaming is entirely harmless, and bubbles develop as gases form through the fermentation process. So long as the ferment smells and tastes okay, bubbling and foaming are fine.

More Resources

The Art of Fermentation, written by Sandor Katz, is an incredibly comprehensive resource. Reading through it, you can really feel Katz’s love for fermentation. Pretty much every serious enthusiast has this book on their shelf. Another amazing book is The Noma Guide to Fermentation, which was published rather recently in 2018.

If you’re into YouTube, maybe you already know about Bon Appetit’s It’s Alive series with Brad Leone. Joshua Weissman and Pro Home Cooks also put out a lot of great fermentation content.

As for websites dedicated to fermentation, Fermented Food Lab and Cultures for Health are two to bookmark!

Final Thoughts

Perhaps the biggest misconception about fermenting is its difficulty level. Surprisingly it doesn’t take any special equipment, unless you count a scale, and it’s pretty hard to mess up. Even if you make a terrible mistake, the only consequence is losing some veggies. So dive in and start fermenting today!

Feel free to leave any questions below, and tell me what you plan on fermenting first!

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