Lactic acid fermentation – intro

Fermentation is an ancient practice used to preserve food, help digestion, make nutrients more available and, most importantly today, introduce and improve flavors ​[1]​. People have been fermenting food since ancient days and it has even been proposed that beer making is the very reason we even gave up our hunter-gatherer lifestyle ​[2], [3]​.

Fermentation is often classified as any food transformation that relies on microorganisms, such as yeast for beer and bread making; fungi for making soy sauce, tempeh and miso; and bacteria to make kimchi, sauerkraut, and non-dairy yoghurt. Very often multiple different families of microorganisms are involved to create a plethora of flavor compounds. For instance, both yeast and bacteria are involved in fermenting cacao beans and for making kombucha.

Fermentation at home

Microorganisms are everywhere. Fermenting foods is all about creating an environment that promotes the growth of one or a few species of microorganisms while suppressing the growth of other organisms that are either harmful or just create unpleasant flavors. Often the microorganisms will create this protective environment themselves if you help them get a foothold. You just have to create a good environment for the particular organism you have in mind.

Phrased like this, it might seem like you need to be a microbiologist to ferment your own food but it is really easy. After all, as a species, we have been working together with microorganisms in this fashion for thousands of years. Yet, we have only been aware of their existence for a few centuries, ever since Dutch lensmaker Antonie van Leeuwenhoek described his little animals, animalcules, to the Royal Society in the late 17th century ​[4], [5]​.

So how do you create a good environment for your little helpers? Depends on which ones you want help from.

Creating a pleasant LAB environment

In lactic acid fermentation, vegetables are submerged in salt water to create a high salt level, anaerobic (no oxygen) environment. This environment prevents any species that either require oxygen or can’t stand high salt levels from growing. This leaves lactic acid producing bacteria (LAB) (e.g. Leuconostoc mesenteroides, Lactobacillus brevis, and Lactobacillus plantarum) free to munch on all the sugars present in the vegetables and create lactic, acetic acid, carbon dioxide and other tasty byproducts. This acid production reduces the pH of the environment (i.e. making it more acidic) and further helps protect the LAB and kill any unwanted stragglers that survived the salt and anaerobic environment.

A few things to keep in mind

To reduce the number of undesirable organisms from the start, you should clean your jars and wash your hands. Soap and water is enough, no need to boil your jars or hands. (Sterility is not a big issue as the LAB will defend themselves once they are able to.)

During fermentation, you can either keep the lid closed or slightly open. Keeping it closed will create a buildup of carbon dioxide and will pressurize the jar. Open the lid slightly every day to release the pressure (‘burp’ it). Keeping it closed will carbonate the ferment and give it a slight fizziness

To give your microorganisms an extra-strong start, you can use a method called inoculation or back slopping, sometimes referred to as ‘using a starter’ (especially in sourdough baking). You simply pour some old liquid from another ferment into your new batch. This helps reduce the pH and add a large number of your bacteria from the get-go. If you have a ferment that turned out very well, you will also ensure that you get your own, confirmed nice, herd of helpers. Wild lactic acid-fermentation is by its very nature random and you will get variations in flavour and fermentation rate depending on where and when you do it. Back slopping helps you give more even batch-to-batch results but you loose the excitement of getting different bacteria every time. Back slopping can be compared to using bakers yeast (back slop method) or sourdough (wild ferment).

Where do I start?

What vegetables should you try fermenting? The number of fruits and vegetables lactic acid-fermented in different cultures is enormous and there are bound to be several recipes you will love. We always have homemade kimchi in the fridge and I have come to really like fermented mushrooms (see recipe at end of post).

Fermentation sources

There is a ton of information on different blogs and in cooking shows. If you haven’t watched Brad Leone’s fermentation experiments on the Bon Appetit youtube channel, you really should.

My favourite book on the topic is Noma’s Guide to Fermentation in which Redzepi and Zilber combine the biology and cultural history of a wide range of ferments, from lactic acid fermentation to vinegar, miso and kombucha. The book features very detailed how-tos and novel recipes, such as LAB fermented plums or gammeldansk vinegar (a bitter, Danish spirit).

Another iconic book in this field is Sandor Katz’ The art of fermentation where Katz has collected a huge amount of different fermentation traditions from all over the world. This book does not have many details on procedures and recipes and is better used as an inspiration for what you can try once you’ve gotten your feet wet. Katz also runs a fermentation blog and forum at WildFermentation.com.

Scientific literature

With the large number of hobbyists in the field and the multiple blogs on the topic, there is a lot of conflicting information or personal speculations around. In writing this post and its companion post on safety and chemistry, I tried to delve into the scientific literature, esp. when it comes to safety. If you want to try your hands at your own research (which you really should) but you’re not sure where to start, you can check out this great post on “Why you should read scientific articles, where to find them and how to get good at it”.

Safety and chemistry

Since fermenting foods is all about getting microorganisms, including bacteria, to grow, it is only natural to ask Is it safe? After all, many bacteria cause diseases. The short answer is that it is quite safe if you clean your jars and get a good growth of LAB. The longer answer became too long and got moved to another post.

After reading a few recipes, you will see a lot of people telling you to use bottled or filtered water and avoid iodine like the plague. Why is this? A longer answer can be found in my Nitty Gritty post, the short answer is that it doesn’t matter that much.

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Lactic-acid fermented mushrooms

These garlicy, tangy fermented mushrooms are amazing as a condiment for almost any food or just eaten on their own. The pickling juice can also be used in mashed potates or gravy ffor extra flavour.

Course condiment, Side Dish, Snack

Prep Time 15 minutes minutes

Servings 1 jar

Author Henrik Persson | Veganphysicist.com

Ingredients

• 1 L mushrooms
• 30-40 g salt
• 1 L water

Spices

• 2-3 cloves garlic
• 1-2 bay leaves
• 1 tsp dried thyme
• ¼ carrot, sliced
• 5-10 black pepper corns

Instructions

• Dissolve salt in water to make a 3-4 % brine.
• Rinse mushrooms.
• Fill a clean jar with the musrhooms and spices.
• Cover in brine. Make sure the mushrooms are submerged, e.g. by adding a weight on top.
• Let ferment at room temperature for 3-5 days, until slightly sour tasting.
• Serve as a condiment or on their own. Leftover brine can be used in sauces or mashed potatoes.