How Do Cod Livers Ferment?

How do cod livers ferment?

One of the most common questions we see is ‘how do cod livers ferment?‘ We’ve also bee told that you cannot ferment cod livers. We have even seen the more confused (and often more vocal) of critics claim that you cannot ferment oil. They actually are right but have the wrong end of the stick. You cannot ferment oil (cod liver or otherwise), but no one is claiming to have fermented oil. Our oil is released by fermenting cod livers. It is the livers that ferment, not the oil.


Requirements for fermentation

Fermentation needs food for bacteria to eat and break down. This is almost always in the form of sugars or complex carbohydrates. Unsurprisingly, you will find fermented foods like sourkrahut, bread or even beer are plant-based. Plants are naturally high in carbohydrates and ferment very well.

It is easy to assume that meat (such as liver) is nothing but protein and fat, and so cannot ferment. Whilst these macro-nutrients are in abundance in meat, there is still a significant amount of carbohydrates present. Liver, in particular, is quite high in carbohydrates. In many animals, including humans and cod, the liver stores large amounts of glycogen, which is a complex carbohydrate used as an energy reserve. It is glycogen that bacteria can ferment in cod livers.


How to ferment cod livers

We have already ascertained that cod livers do contain something for the bacteria to eat – glycogen. To ferment the livers properly (as opposed to just letting them rot) you need to ensure the right bacteria do the fermenting. This is done with salt. Most bacteria cannot tolerate high salt concentrations, and so mixing the livers with salt prevents most bacteria from surviving. This includes the common foodborne pathogens, as well as a whole host of others. The only bacteria to survive and ferment the livers are called lactobacillus, and these are a type of probiotic. Bacteria that can tolerate high salt concentrations are called halophilic bacteria.

These probiotic bacteria break down the livers and produce acid, which lowers the pH. This lowering pH inhibits even more bacteria and eventually kills off the Lactobacillus species. This process breaks down the livers, which releases the oil. The process really is that simple.


Examples of other fermented meats

Still sceptical? You’d be surprised how common fermented meat products are:

1. Pepperoni is a fermented pork product, which uses a high salt content to select the bacteria. There are many variations of these fermented hams throughout the Mediterranian.

2. Worcester sauce – a popular condiment (at least in the UK) – is made from fermented sardines. Its production is very similar to our fermented cod liver oil.

3. nước mắm (pronounced nuoc mam) is a fermented fish sauce from Vietnam. There are several commercial variations of this sauce in America. Like fermented cod liver oil, it is made by fermenting fish in salt. There are 1000s of variations of this sauce throughout Asia.



Cod livers can, and do ferment. The way they ferment is very similar to a number of very popular sauces and meat products throughout the world. Fermenting meat is not so alien as it initially sounds.


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fermented cod liver oil and beeswax