If you have not tried to ferment foods, the process can seem scary. Like most people, I, too, was raised with the concept that food did not sit on the counter or it would rot. So I am not surprised at all if people are leery about the process. I thought perhaps a short science lesson was in order. This will not be too technical, just enough to help you understand exactly how food ferments and why it can be done safely. I will admit, I had a few interesting results in the early days, but once I understand the science, my ferments have been amazing.
The key piece of information you need to know is that most fermentation processes are anaerobic, which means that they work without the use of oxygen. More importantly, oxygen is actually the enemy and if you would like some nice, furry mold to form on your ferments, then just let some air get at them. Milk kefir, water kefir, sauerkraut, kimchi and cultured vegetables are all made using an anaerobic process. Kombucha is the one exception as it does well when exposed to oxygen.
Sauerkraut, kimchi and cultured vegetables are submerged in a brine and as long as vegetables stay submerged, at least in the early days, they will not mold and will ferment to develop the strains of good bacteria that make them so beneficial to us. Brine is combination water and salt, with the salt acting as a means to inhibit bad bacteria so that the good bacteria can get started. Most containers for making these items will require a lid that can be used to seal out the air, although in the case of sauerkraut, weights are also often used to hold the cabbage below the liquid.
In the early days of the fermenting, it is essential that the food or in the case of kefir, the grains, stay submerged as there will be oxygen inside the jar in the beginning, despite the lid. Once the good bacteria starts the fermentation process, gasses will build inside the container and create a vacuum, which means there is no oxygen inside the container. In this environment, mold and undesirable organisms cannot grow and the good organisms can continue to ferment in the anaerobic environment.
Milk kefir and water kefir are also both anaerobic but unlike brined-based ferments, the good bacteria is being added by using the kefir grains. They start to reproduce and ferment the water or milk immediately. The resulting fermented product is ready within 24-48 hours unlike brine-based ferments which can take 1- 4 weeks. Also kefir grains do not float and are protected from air by the milk or water. Since they are also going to be in an airtight container, then inside environment will quickly produce gas and create a vacuum.
Here are a few quick tips to help ensure success when you ferment:
- Always leave an inch of space in the container to allow for gas build-up. Too much gas and the container can explode and by explode, I mean crack and leak – it does not actually explode like a bomb and blow up to spew fermented goo everywhere. I just like the word “explode” – it is just so much more expressive. If you hear a hissing sound, then there is probably a crack in the jar.
- If you are fermenting for a couple of weeks or more as you might be when making kimchi or sauerkraut, loosen the lid after 1 week or so to let some air out but then screw back on tightly. Do this only once during the whole process. Don’t keep opening it or your ferment will spoil. This is known as burping the bottle. There are special air lock lids which have a contraption on top to allow air out as needed. I have not found them helpful.
- If you are fermenting vegetables and some float to the top, turn the jar upside down, once a day which will cover the floaters with brine. Once the gas builds up inside, you no longer have to do this.
- All fermented foods have an acid ph. Good bacteria produce lactic acid and sometime acetic acid as part of the fermentation process. Bad bacteria and mold do not grow in acid so to help you understand the process, buy some ph papers. Test the ph at the beginning and at the end so you can see that is has indeed fermented and that the food and liquid has gone from a neutral ph to an acid ph (usually around 4).
Happy fermentation! I would love to hear if you have any fermentation stories to tell.