Lacto fermentation is a natural, biological process involving beneficial microorganisms. They cause a change in the make-up of food products, creating lactic acid which lowers the pH (more acidic). Bacteria are also responsible for increasing the nutritional value of the fermented food.
Fermented food is easier for the body to assimilate as it is already “chewed and digested” by the microorganisms. Therefore, vitamins, minerals, enzymes, and other nutrients can be more fully absorbed.
Fermented food processed by beneficial microorganisms is highly bioavailable
Consuming fermented food helps the digestive tract to remain in balance.
Lacto fermentation describes a biological process when microorganisms convert sugars in vegetables and milk into lactic acid.
The more lactic acid present in food, the more acidic the it tastes. Lactic acid a main reason why fermented food feels tangy and refreshing.
- prevents growth of harmful microorganisms
- promotes growth of beneficial bacteria
- increases bioavailability of nutrients
- help control intestinal infections
- acts as a natural preservative
- makes food easier to digest
Three simple principles
These simple principles apply to most vegetables fermented at home. A successful fermentation means sticking to these principles.
Unwanted microorganisms can disturb the fermentation process by producing butyric acid and other bad-smelling substances. Because of this, the final product may develop a bad taste and texture. This has happened to me a few times so I’ve learned much from my own mistakes.
The main principles for a successful fermentation
- Correct salt concentration
- Correct temperature
- Absence of oxygen
1. Salt concentration
Between 1-3% of salt is viewed as a good range. I use Himalayan or sea salt in all my recipes.
Lactic acid producing bacteria often tolerate high salt concentrations. Adding salt promotes fermentation and prevents the growth of non-desirable organisms.
Starter cultures work better when adding salt
The bacteria strain Leuconostoc (found in kefir and sauerkraut) has a high salt tolerance and often initiates the fermentation process. Salt extracts juice from the vegetables and creates brine.
Try using the excellent celery juice as brine. It has properties that help preserve the vegetables fresh. However, the final product will not taste celery, in fact, you hardly feel it at all. But for this you need a juicer.
Traditional fermentation without a starter
This is also called a “wild fermentation” and is still used in many places. Works well if you know what you’re doing. How does is work?
Vegetables are placed in a layer of about 2.5 cm (one inch) depth in the fermenting container. Salt is sprinkled over the vegetables. Another layer of vegetables and salt is added, and this is repeated until the container is three-quarters full. A cloth is placed above the vegetables and a weight added to compress the vegetables and assist in the formation of a brine which takes about 24 hours. As soon as the brine is formed, fermentation starts and bubbles of carbon dioxide appear. It ferments for7-15 days, then stored in a cool place.
Most lactic acid producing bacteria work best at temperatures of 64 to 72 degrees (18 to 22ºC). However, there’s a wide range of possible fermentations making each batch unique.
Some general facts to consider:
- Most probiotic bacteria prefer 68 to 86 degrees (20 to 30ºC) (fermented vegetables, sauerkraut, fermented dairy)
- Some bacteria, like the thermophiles (in yogurt) prefer a bit warmer temperatures 120 – 130 degrees (45-5OºC, close to a radiator)
- Other bacteria like it cooler. One example is Leuconostoc species involved in lacto fermentation. They have an optimum of 64 to 72 degrees (18 to 22ºC)
- Generally speaking, temperatures above 72 degrees (22ºC), favor more the lactobacillus species.
If it’s too warm when fermenting it can cause problems with mold or unwanted bacteria. I’ve found that using a starter culture helps to control the batch.
Even though some bacteria require oxygen for their metabolic activities, lacto-fermentation at home works best in the absence of oxygen. Using air-tight jars is therefore important.
During the first days of fermentation pressure builds in the jars. Therefore, don’t screw the lids on too tight, or open the lid for a second to let the gas out.
After fermentation lids should be screwed on tighter to keep air out.
Three phases of lacto-fermentation
It starts with “breaking down” of substances in the vegetables. This first phase if short, only a few days. You might see bubbles and brine coming out of the jars. This is normal. During the first phase, most harmful microorganisms are destroyed as the batch turns increasingly sour.
Good bacteria are now in complete control of the jar and consume sugars contained in the vegetables. Lactose, glucose, fructose, and sucrose are all converted by the bacteria into lactic acid and other potent substances. This gradually increases the bio-availability of nutrients.
The level of acidity increases slowly in the brine and this creates the familiar tart, tangy flavor in fermented food. The acidity helps preserve the vegetables since most harmful bacteria don’t survive in such an environment. The more lactic acid produced, the more acidic the flavor.
Storing the jars in a cool place slows down fermentation. However, the beneficial microorganisms are still alive, slowly consuming carbohydrates and producing a range of potent substances. The bacteria can stay alive in the jars for many months. The longer you store the jars, the more tart and complex aromas are created.
Using starter cultures
Several microorganism species are involved in the natural or wild lacto- fermentation process. These naturally occur on raw vegetables and milk.
A starter culture helps to control which bacteria strains will take control in addition to the ones naturally present on the veggies. Usually bacteria in the starter culture will dominate the process from start to end.
- More lactic acid
- Fewer problems
- Predictable result
- Stable fermentation
- Easier fermentation
- Can be consumed faster
- More beneficial bacteria
In addition to desirable bacteria, there are also undesirable micro-organisms present on vegetables which can interfere with the fermentation if allowed to multiply unchecked.
The quality of the final product depends largely on how well the undesirable organisms are controlled. Some bad bacteria use protein as an energy source, thereby producing unpleasant odors and flavors.
Bacteria involved in fermentation
Here are a few examples of microorganisms involved in lacto fermentation of different ingredients.
Yogurt: Fermenting milk into yogurt involves Lactobacillus bulgaricus, Lactobacillus acidophilus, and Streptococcus thermophilus.
Kefir: Produced with cow, sheep, goat milk or even soy, rice or coconut milk. Originates in the Caucasus region. Kefir contains strains of Lactobacillus Caucasus, Leuconostoc, Acetobacter species, and Streptococcus species. Beneficial yeast is also involved.
Sauerkraut: Fermented cabbage. Strains of Leuconostoc are involved as well as Pediococcus and Lactobacillus strains like Cucumeris. Lactic acid bacteria are the primary group of organisms involved in sauerkraut fermentation. Read more on preparing sauerkraut.
- Leuconostoc mesenteroides – acid and gas producing
- Lactobacillus plantarum – produces acid and a little gas
- Lactobacillus pentoaceticus – acid and gas producing
Miso: Japanese ways of fermenting rice, barley and mostly soybeans. Miso is a natural food containing healthy microorganisms such as Tetragenococcus halophilus. As probiotics bacteria can be killed by over-cooking, add the miso to soups or other foods just before they are removed from the heat. Or use miso without any cooking at all.
Natto: Soybeans fermented with Bacillus subtilis. It contains enzymes and compounds with exceptional health benefits.
Kimchi: Often made from cabbage, radish, cucumber and other vegetables and seasonings like ginger, garlic, scallions and many other. It contains a number of bacteria, especially Lactobacillus kimchii.
Kombucha: A kombucha culture often contains Gluconacetobacter xylinus and one or more of the yeasts Saccharomyces cerevisiae, Brettanomyces bruxellensis, Candida stellata, Schizosaccharomyces pombe, Torulaspora delbrueckii, and Zygosaccharomyces bailii.
Lacto fermentation in all forms is an amazing process. Be sure to consume plenty of it!