How do fermentation airlocks work

Unlike humans and fish and plants, some bacteria and yeast can manufacture high-energy molecules similar to ATP without using oxygen. This process is called anaerobic respiration. When fermenting, we want this kind of anaerobic respiration. The byproducts of anaerobic respiration depend on which organisms are involved. CO2 is always one byproduct. Alcohol and lactic acids are other possible byproducts, along with the high-energy molecule NADH.

This is why anaerobic respiration is necessary to make the alcohol in beers, wines, and spirits. When fermenting cabbage for sauerkraut, bacteria engage in a different kind of anaerobic respiration than yeast.

Lactic acid is what gives fermented foods their sour, acidic taste. An anaerobic environment kills any competing bacteria or fungus that would use the sugars to make stuff other than lactic acid or alcohol. With less competition, the yeast and bacteria can better perform their job of making alcohol and lactic acid. Also, some of these bacteria are fickle. They prefer to use aerobic respiration if they have the chance but will resort to anaerobic respiration when no air is present.

Therefore, to get these kinds of bacteria to perform fermentation, you need an oxygen-free environment. The airlock helps you keep an anaerobic atmosphere when fermenting.

It prevents air from entering your fermentation vessel while still allowing the CO2 made during fermentation to escape. At some point, the pressure would overcome the strength of your lid. The resulting beer geyser is a messy situation.

Airlocks help us avoid beer or kraut geysers by letting the CO2 escape from the fermentation vessel into the surrounding room. Since the airlock prevents air from entering the fermentation vessel, the anaerobic atmosphere remains and the fermentation continues! There are a couple of common models of airlocks, but they use the same principle. The water in the airlock acts as a barrier for the air getting into to fermentation vessel.

Also, is it necessary to use a follower? No head space is necessary when using an airlock, but you can freely have head space too. The downside to having oxygen in the jar while using an airlock is that there may be some mold spores potentially in the air within the jar. I have been fermenting without an airlock for years.

Just a glass jar with the metal lid. My ferments always come out great. However, it is a pain to babysit the jars and have to loosen the lid at least once a day to let out the gasses.

So I decided to purchase some lids with airlocks. Thankfully I decided to test them out making just 2 jars using the airlock and 2 jars without, using my old method of loosening the top daily. The vegetables in the jars without the airlock looked like usual, nice and healthy, nice color, still having a little bubbling action too.

The vegetables in the airlock jar looked gray and dead. Normally I let the process go for longer. But I decided to open the airlock jars. Only to find mold growing on top and a terrible odor. This is the first time I have ever had to throw out a batch of vegetables. Needless to say, I will go back to using a jar and a regular lid. Three days into ferment process and I see spots of white mold on top of some of the ingredients.

What is wrong? The airlock prevents molds from entering the container once it is on. I imagine you had some mold on your ingredients prior to placing the lid on the container. Having your ingredients submerged would likely have prevented the mold from taking hold as well as mold generally needs a food source and oxygen.

Good luck. My 2nd batch taste great, thanks for the help. The S-shaped airlock features two vertical chambers connected by a sort of drain trap. Either airlock will suit your fermentation needs, but brewers sometimes prefer the three-piece model for primary fermentations which carry the highest risks of clogging and reserve S-shaped models for secondary fermentation and aging. The sole purpose of any airlock is to allow an otherwise sealed fermentation environment to relieve internal pressure.

When an airlock bubbles, it simply means that the air pressure inside the bucket or carboy is sufficiently high to push up the little column of water and relieve the pressure.

Sometimes the grommets or stopper fails to properly seal with the airlock itself and lets pressure escape with no bubbles. Temperature also plays a role. The colder the wort, the more carbon dioxide it absorbs before gas begins to vent. This is especially true for cold-fermented lagers, which may ferment for several days before the airlock begins to bubble if ever.