What is lacto-fermentation?
Lacto-fermentation is a way of preserving food that has been part of traditional diets all over the world for thousands of years. Food is fermented at room temperature using lactic acid as a preserving agent.
Does lacto-fermentation involve milk products?
No, the “lacto” part of the name comes from the bacteria, Lactobacillus, which get their name from the way they turn lactose and other sugars into lactic acid. Some recipes call for whey (strained from yogurt) as a starter, but I don’t use this in my fermenting and it’s worked out fine.
Won’t leaving food at room temperature poison me?
When I made my first batch of sauerkraut back in 2012, I was convinced I was going to poison myself. How could food stay at room temperature for a week and still be okay to eat, especially in a warm climate like Brisbane?
The secret to successful fermenting is to create an environment where the Lactobacillus bacteria can grow and proliferate, while inhibiting the growth of bacteria that can cause food to spoil. Lactobacillus bacteria are fairly salt-tolerant, so by adding salt to the vegetables initially, the growth of undesirable bacteria can be slowed, while the Lactobacillus bacteria are unaffected.
The Lactobaccillus bacteria then begin to metabolise the sugars and carbohydrates, producing lactic acid and carbon dioxide. The carbon dioxide ensures that the environment stays anoxic (oxygen-free), further inhibiting the growth of undesirable organisms. The lactic acid lowers the pH of the ferment, again making it unsuitable to growth of undesirable organisms.
So if you have fermented correctly, there are three evironmental factors working against the growth of moulds, yeasts and undesirable microorganisms: high salt content, low oxygen content and low pH.
Do I need to use a starter?
Some recipes call for whey or a commercial starter to innoculate the ferment with some Lactobacillus bacteria. This is not necessary, as the vegetables themselves will generally have enough bacteria on them to begin to ferment. However, I do sometimes use a bit of brine from a previous batch as a starter, so if it makes you feel better to use a starter, go ahead!
How do I know if the lacto-fermentation has been successful?
A successful ferment will start bubbling within a day, it will smell sour, and the vegetables will be crunchy and taste pleasantly sour. There may be a small amount of white scum present on the surface – this is safe and you can just skim it off. There will also be a small amount of sediment in the bottom of the jar, this is just a byproduct of the fermentation (similar to the sediment produced in homebrew beer).
An unsuccessful ferment may be slimy, smell bad or turn a different colour. In two years, I have only had two batches go wrong, and it was immediately obvious. One batch of salsa went bad in very hot weather and I could tell because of the smell, and a batch of daikon radishes went mouldy because they were not completely submerged in the brine.
Here are a few handy guides written by people with a lot more experience with lacto-fermentation, that can help you troubleshoot your ferment:
A great troubleshooting guide to fermentation from the National Center for Home Food Preservation. They refer specifically to fermented cucumbers (pickles), but the guide would apply to all types of fermentation.
Another great troubleshooting guide put out by North Carolina State University.
And a very detailed guide from the Food and Agriculture Organisation of the United Nations.
Want to give it a go? Here are some easy recipes for beginners:
Sauerkraut (Economies of Kale)
Lacto-fermented salsa (Economies of Kale)
Lacto-fermented carrot sticks (Economies of Kale)
Lacto-fermented garlic (Learning and Yearning)
Lacto-fermented veggies (Simply Smiles)
Lacto-fermented spicy carrots (Happy Mothering)
Cortido (Just Making Noise)
Lacto-fermented radishes (GNOWFGLINS)
Next week I will talk about the benefits of lacto-fermentation, both in terms of health and food preservation.
Do you have any more questions about lacto-fermentation? Do you have any recipes to share?