Benefits of fermented mushrooms
Firstly, it’s very easy to ferment mushrooms, plus the process increases many of their inherent nutritional and health benefits.
- It causes a significant increase in protein content.
- A decrease in carbohydrates and fat.
- It will increase the quantity of several important minerals including calcium, magnesium, potassium, manganese, iron, and sodium (to reduce sodium use calcium chloride CaCl instead of plain cooking salt (aka sodium chloride or NaCl).
- Maintains many of the health attributes found in raw mushrooms
- Releases several beneficial components found in the mushroom that would not otherwise be digested.
- It’s a superior source of both pre and probiotic material for your body.
How does fermentation work?
If you are new to fermentation, here's a quick summary of how it works.
Lacto fermentation relies on the fast growth of Lactobacillus bacteria which will create acids (like vinegar) decreasing the pH. These lactic acid bacteria are often referred to as LAB. The increase of acidity kills harmful bacteria and is what gives the ferment its zesty and sour taste.
The fermentation process takes place in an air-free (anaerobic) environment, which is usually achieved by performing it underwater. This water comes from the liquid drawn out of the mushroom (or plant) by salting it. This saline solution also inhibits the growth of other undesired organisms (like moulds, yeasts and some harmful bacteria).
What are Lactobacillus bacteria?
Lactobacillus bacteria is considered a beneficial or healthy bacteria which is also an essential part of our bodies. It is also used to make yoghurt and cheese. They are present in our gut, where they also naturally ferment food to release nutrients that our body would otherwise not be able to digest. They also form the basis of healthy gut flora.
Why is fermented food good for our bodies?
Eating fermented food provides 2 healthy outcomes. 1) it is a way for us to populate our bodies with important bacteria (pro-biotic) to maintain a healthy body. 2) It also introduces a food that can not be digested in the upper parts of the digestive tract, so acts as food for the healthy bacteria already living deeper in our gut.
On a side note, one of the outputs of fermentation is gas (generally CO2) so you’ll know how well your body is fermenting things well by the amount of gas you produce.
How to ferment mushrooms
The following information is fairly technical in places, as it's written primarily for people familiar with the fermentation technique. For the newcomer, it does a good job of explaining the fundamentals. Don't be put off that it appears difficult because it isn't. It is a very simple and natural process. There are several recipes at the bottom of this article that will step you through the process.
Are mushrooms safe to ferment?
Mushroom fermentation has a long history. It is the preferred method of several traditional cultures (eastern Europe and Asia) as a way of preserving and storing mushrooms. More recently, mushroom fermentation has been rigorously tested through lab research to ensure food safety. This testing has mushrooms categorised as very safe for fermentation.
What preparation is required?
Like all ferments, only the best and freshest mushrooms should be used. Cleaning is an important process especially if mushrooms are foraged. Wash in cold running water and remove any damaged or rotting portions. Take care not to damage the fruit. For mushrooms with thick woody stems, only the caps are used. For mushrooms like Oysters or smaller mushrooms, you can use the whole thing. If the cap is thick, it should be sliced.
Do I need to blanch first?
The main purpose of blanching is to remove excess air and reduce volume, so more can be packed into the container. Mushrooms have enzymes and other undesirable bacteria that can lead to a fresh mushroom “going off” very quickly. So, unless you have a starter culture to deal with this, it would be best to blanch the mushrooms first.
- The recommendation is 3-4 minutes in boiling water.
Note: Care should be taken as blanching will also destroy many of the mushroom's unique health properties. In lab tests, it was found that the total phenol content decreased by 60% and the antioxidant capacity decreased by 54%.
Should I add salt?
Salt is used in the fermentation process to draw out liquid from the mushroom (thereby submerging it in water). This saline environment inhibits many other bacteria and organisms that will spoil the ferment but does not affect the LAB.
People experienced in fermentation will often rub the salt in by hand, rather than mixing it with water first. The contact with the hands helps introduce lactobacillus bacteria.
Note: Table salt (with iodine) should be avoided. Salts not containing iodine are often labelled as kosher or pickling salt. Here's a link to info regarding fermenting and salt
2% salt is recommended
Do I need to add sugar?
The mushroom's carbohydrate profile, including complex sugars like polysaccharides, allows them to be fermented without the addition of sugar.
If sugar is used 1% is recommended.
Adding sugar would be recommended if not using a starter culture.
Is acidifying (Adding vinegar) required?
If you follow the guidelines in preparing the ferment, you generally do not need to add additional acids like vinegar. Adding vinegar is often used in pickling mushrooms (a similar food preservation technique) where fermentation is not the goal and you wish to speed up the process. Note achieving an acidic pH level of less than 4.5 is essential in making and keeping the food safe.
If using vinegar we recommend a raw cider vinegar like Bragg Certified Organic Raw Apple Cider Vinegar
Do I need a starter culture?
Due to the mushroom's high moisture content and neutral pH, a starter culture or back slopping is recommended. These “back-slops” are best sourced from an earlier and successful ferment. The “juice” from a sauerkraut ferment has been found to work well.
Mushrooms can be fermented without adding a culture. In this case, it may be prudent to add some vinegar to increase acidification in the early stage, and also add some sugar to get the LAB producing sooner.
Note: Lactobacillus Plantarum (a type of LAB culture used for fermentation of plant material) is mainly used for the fermentation of mushrooms. It has also been found that the use of the L. Plantarum 299v probiotic strain enhanced an increase in the antioxidant activity and other phenolic compounds of fermented mushrooms to a level similar to that of fresh mushrooms.
How long do I need to ferment mushrooms?
Fermentation is usually carried out at a temperature of 18 to 26 °C for a period of several to 30 days. Mushrooms fermented at a lower temperature (around 20 °C) have been reported to have better quality.
If the final product requires longer storage, the safest length of time would be a ferment of +18 days. This ensures that the pH level has decreased (aim for a pH less than 4) to the point that all undesirable bacteria and yeast should have been eliminated. A 30-day ferment should have a pH of around 3.5.
Note: Populations of undesirable bacteria may increase in the first few days of the ferment, so for shorter ferments, it would be appropriate to add some vinegar.
Once fermented, how long will they keep?
Generally, this will depend on how cool it is kept. It should be good for at least 4 weeks but if stored properly, it should remain stable for up to 6 months. The cooler the better. Adding a small amount of oil may also help durability for longer storage.
Pasteurisation is generally not required but it may help to improve the quality of longer stored products. Pasteurisation will not affect the antioxidant capacity and the content of phenolic compounds, however, it will destroy the probiotic capacity by killing the live lactose bacteria.
Much of the information provided here was sourced from