Fermentation: Strange Ch-Ch-Ch-Changes: Lacto-Fermentation

This is a part of my series exploring fermentation at the cooking school. To start from the beginning or see a list of previous posts, click here.

Fermentation is the transformation of food by microorganisms. Whether bacteria, yeasts, or mold, these microorganisms all produce enzymes which, in the absence of oxygen convert sugar into another substance - alcohol, acid (cheese, pickles, kombucha), and carbon dioxide (breads and effervescent drinks) to name a few (The NOMA Guide to Fermentation).

Sight unseen (though not without smell), these small organisms work wonders to transform ingredients into the funkier, fruitier, umami-rich versions of themselves. At the school, we employ a number of these processes, eating and serving the results as components of dishes and straight from the jar. Over the next week, I’ll be posting a few examples, with a short idea of the biological processes at play and some recipes for you to try at home. So, to start:  


The fermentation you’re probably most familiar with (other, perhaps, than alcohol) is lactic acid (lacto-) fermentation, or fermentation using only salt and the naturally occurring or “wild” Lactobascilli bacteria already found in the air and your food. These fermentations include sour pickles of all kinds, sauerkraut, giardiniera, kimchi...anything with that distinctive one-two punch of salt and tang.

As previously mentioned, fermentation can be most basically thought of as a controlled rot. An attempt to make the environment in your crock, bucket, or jar as ideal for specific good bacteria, and as inhospitable for bad, as possible. Lacto-fermentation provide a great opportunity to illustrate this as the process itself is so simple: weigh your ingredients, add 2% salt by weight, cover and wait until they’ve reached the level of sour you’re looking for.

Lactobacillales (LAB) are sugar-loving, salt-tolerant bacteria, living in and around your food. They’re also anaerobic, meaning they can survive in the absence of oxygen. Over the course of a lacto-ferment, these LABs consume the sugars in your food and convert them to lactic acid, the source of the sour. Sealing your container and adding salt creates an environment in which LABs can propagate and do their thing while simultaneously preventing other wild bacterias from doing the same.

So, to lacto-ferment: weigh, salt, wait. Though fundamentally the same across applications, there is room for variation where the ingredients demand: you may want to dissolve the salt in water to create a brine for pickles; for cabbage ferments such as sauerkraut and kimchi, you’ll want to rub the salt between their layers, or even tamp them down a bit after salting, to release some of the natural water in the leaves; we even ferment liquids such as roasted red pepper puree for our harissa paste by adding to a 2% salt-brine, and keeping submerged with water-filled Ziplocs placed on top (once fermented as desired, the puree is then dehydrated in a low oven - or by the sun if you’ve got the time and like to kick it old school); in all applications, consider adding herbs, spices, garlic, peppers, and other flavors to suit your taste, just keep in mind that these will concentrate over the course of the ferment, so be sparing.  

Recipes for pickles of all kinds are pretty abundant online, as are recipes for everything from basic sauerkraut to traditional kimchi. So, to change it up, I’d like to share Ian’s process for Lacto-Fermented Potato Chips. Just imagine salt and vinegar chips, straight from the fryer, no powders necessary.

Lacto-Ferments, From Top: Harissa Paste, Pickle ‘Salad,’ Kimchi, Pickles with Headcheese