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Lactic fermentation and How it works

by Hannah Geddes |

We've had a few requests lately to dive a bit deeper into some of the science behind fermented foods, so lets start with one of the old-school preservation methods - lactic fermentation.

Some of your favorite fermented food like kimchi, sauerkraut, pickles, sourdough bread and yogurt are all created using the lactic acid fermentation method. This is the sour taste you can taste. 

What is Lactic acid Fermentation?

Lactic acid fermentation is a metabolic process where glucose or the other 6-carbon sugars - including disaccharides of 6-carbon sugars like lactose or sucrose - are converted into cellular energy and the metabolite lactate, which is lactic acid in solution. It is an anaerobic fermentation reaction and it occurs in some bacteria and animal cells such as muscle cells. In a nutshell, this fermentation transforms sweet (simple carbohydrates) into sour (acid).

How does it work?

When bacteria metabolize carbohydrates and sugars, they produce lactic acid. This lowers the pH of your ferments to less than 4.5, which in itself preserves your fermented foods and drinks. In fermented foods, the salt added helps set the environment for the bacteria to get to work.

In dairy products such as milk kefir and yogurt, we add lactic acid bacteria as a starter culture for the milk. Therefore, all you need to produce yogurt and other fermented milk products is; milk, lactic acid bacteria, time and a specific temperature. When you add lactic acid bacteria to ferment the milk, the bacteria begin to multiply. 

At the same time, the lactic acid produced causes the protein in the milk to bind together in a network that makes the milk thick and also releases some aroma. The moment the lactic acid bacteria is added to the milk, temperature and time will do the rest.

Depending on the kind of lactic acid bacteria used and the type of product you wish to make, the fermentation will take place between 20 - 42 degrees celsius and will take about 4 - 18 hours. When the fermentation is done, the milk becomes thicker and the taste will also change. Oftentimes, it becomes stronger and tart.