How to ferment vegetables at home

Fermenting “cosse violette” French climbing beans (left) and fermenting chilli peppers (right)

Apart from the fact that they are tangy and delicious, making fermented vegetables is an easy way to preserve vegetables for many weeks or even months and in doing so, avoid waste. Fermentation works well even if foods aren’t at their freshest (provided they haven’t gone mouldy or slimy) so it’s a perfect way to give wrinkly veg a new lease of life.

What is food fermentation?

Fermentation is a natural process whereby microorganisms – like bacteria and yeast – break down carbohydrates into acids or alcohol. As well as preserving the foods, the acids or alcohol give fermented foods a tart, pickle-like flavour.

Fermented foods can be beneficial for your health. As vegetables are fermented raw, many of the nutrients contained within them are preserved during the process. In fact, fermentation helps to break down nutrients in food, making them easier to digest. In addition to this, the probiotics (i.e. beneficial bacteria) in fermented foods have been associated with improvements in immunity, digestive health and more.

How does a ‘normal’ ferment look, smell and taste?

Vegetable fermentation is generally considered low-risk, but as the acidic flavour may be new to some of us, it’s helpful to know how to tell the difference between a ‘normal’ ferment and one that’s spoiled.

A normal ferment:

  • A pleasantly sour smell and taste
  • White film on the top of the jar (a natural yeast by-product of the fermentation process – just skim off and discard)
  • Sediment at the bottom of the jar or cloudy liquid – this is a sign of bacteria and is nothing to worry about.

A spoiled ferment:

  • Visible mould floating on the top. Some people scrape the top off and eat the ferment, but if in doubt, throw it out.
  • Extremely smelly
  • Bad taste
  • Slimy, discoloured vegetables. Note that it is normal for some green vegetables – like green beans and cabbage – to go slightly brown or pale when fermented.

Recipe: fermented beans

Ingredients:
  • 175g beans – french/green or runner
  • 1 small red chilli (diced)
  • 3-5 roughly chopped garlic cloves
  • 1 teaspoon dried oregano
  • Water*
  • 10-12 grams of sea salt, according to taste**
  • If you have it, a few tablespoons of liquid from another ferment – the bacteria and yeasts within will help get the party started!
  • (Optional) a handful of diced cherry tomatoes or (cool) roasted red peppers

*It is recommended to use dechlorinated water, as chlorine can inhibit the growth of the beneficial bacteria needed for the fermentation process. You can dechlorinate tap water by letting it sit overnight, during which much of the chlorine should evaporate. Otherwise, you can use filtered water.

**Salt is key to fermentation as it creates an environment where ‘bad’ bacteria that cause food to spoil cannot survive. Table salt contains iodine which can prevent the growth of beneficial bacteria, so it is recommended to use non-iodized salt, such as unrefined sea salt.

Equipment:
  • 500ml mason or kilner jar, or fermenting crock. It is not recommended to use jars with metal lids, as the acids produced during fermentation may corrode metals. We do not know if they can also corrode plastics, but it may be best to avoid plastic containers for fermentation, particularly if they are not ‘food grade’.
  • Fermenting weight or small jar to keep the vegetables submerged under the water.
Method:
  • Wash the jar and utensils in hot, soapy water. You may choose to sterilize the jar in boiling water, but many don’t do this – the salt in the ferment should prevent spoilage.
  • Add the oregano, garlic and chilli to the jar.
  • Pack the beans (whole or chopped) and cherry tomatoes (if using) into the jar, pressing down so that it contains as little air as possible.
  • Create a brine by adding the salt and filling the jar with water until almost full.
  • Place the fermenting weight on top of the vegetables to keep them submerged. This prevents them from being exposed to oxygen which can make them go mouldy.
  • Screw the lid onto the jar but not completely. As the fermentation process gets going, carbon dioxide will be produced. If it can’t escape, it could cause the jar to break.

  • The next steps apply to any vegetable ferment: Leave the jar at room temperature away from direct sunlight for 1-2 weeks. After a few days the liquid should go cloudy and bubbles should rise to the surface. The warmer the temperature, the faster the fermentation will happen. To control the process, we recommend keeping it at between 10-20 degrees.
  • ‘Burp’ the jars daily (open them to release any trapped carbon dioxide). Taste it – if the brine tastes too salty, add some water. If not salty enough, add some salt.
  • When the ferment is ready, put it in cold storage, such as a fridge or cellar, where it will keep for several weeks. Deciding when the ferment is ready is a matter of taste. Taste the ferment after a few days, a week, and 2 weeks to see what you prefer.
Other easy recipes to try:
  • Fermented chilli sauce – we’ve served this at events and it’s always a favourite!
  • Easy kimchi – a quick-to-make version of the popular Korean ferment, made from napa cabbage, chilli, ginger and garlic.

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2 thoughts on “How to ferment vegetables at home

  1. Thanks Anais. Will have a go at a batch soon. I’d be interested to know the quantity of salt in weight, as a tablespoon can vary quite a lot depending on how much you fill it and the size of your salt granules. Alan Thawley – Translation and Language Services French/Italian to English alanthawley@yahoo.com

    Tel:   +44 (0)1844 299106  Mob:   +44 (0)77 90412765

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    1. Hi Alan, very good question. I’d say about 12 grams. A rule of thumb when fermenting vegetables in brine is the salt should weight about 5% the weight of the water (1 litre of water weighs approx 1 kilo).

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