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Fermented foods have soared in popularity in recent years and the worldwide market is expected to top £30 billion by 2022. But what exactly are fermented foods and why have they become so popular?

Dr Caroline Gilmartin, a former microbiologist and the founder of fermented foods company, Every Good Thing, explains, “Inside your gut, you’ve got about a hundred trillion microbes living in there. That’s largely bacteria but also yeasts and fungi as well.”

Fermentation prolongs the life of microbes that we know as “good bacteria” and these microbes help you process your food. “When they process your food, they also grow themselves and they produce thousands of chemicals when they do that,” Caroline adds. 

Fermented foods are so good for the gut because they contain probiotics, which have been shown to have a wide range of health benefits, particularly when it comes to improving gut health. This is because fermented foods and drinks contain probiotics, live bacteria and yeast which the NHS says, “are thought to help restore the natural balance of bacteria in your gut (including your stomach and intestines) when it’s been disrupted by an illness or treatment.”

There is also some evidence that the probiotics found in fermented foods can help to prevent IBS.

Beyond the health benefits, fermentation allows you to prolong the life of some types of food and it also is a great way of adding more variety to your diet.

There are plenty of places to purchase fermented foodstuffs from nowadays but fermenting your own food and drink products at home is actually simpler than you might imagine.

Caroline has some specialist advice for getting started with fermentation at home, including a step-by-step guide on where to get started and how to ensure your fermentation process is safe.

Equipment:

• A medium-sized jar with a gasket, like a glass Kilner jar with a rubber seal and clip top. 
• Scales
• A Zip Loc-style food bag

Ingredients:

• Cabbage (one is more than enough to fill one jar, but don’t worry too much about measurements as the technique is down to ratios rather than quantities)
• Salt

You can ferment a range of vegetables but Caroline suggests starting with cabbage to make sauerkraut. “Choose a sweetheart cabbage, which is a softer cabbage, because the vegetables need to be soft before you can use them,” advises Caroline.

You can use any amount of your chosen vegetable as long as it fits in the jar and you correctly calculate your salt-vegetable ratio.

1. Make sure your work surface is clean, wash your hands and make sure your jar is clean and dry

2. Wash your cabbage under the tap and roughly chop

2. Place your jar on the scales, and then set the scales to zero

3. Put your cabbage in the jar (while it’s still on the scales!) and fill with water to shoulder height of the jar, a little before you get to the neck of the container

4. Record the weight of the cabbage and water and then calculate 2 per cent of that weight. This will give you the amount of salt you need to add for the fermenting process. For example, for 400g of cabbage and water, you’ll need 8g of salt.   

5. Add the required amount of salt to the jar and stir to dissolve

6. Next, push the cabbage down as tightly as you can into the salty water so that is fully submerged and there is a layer of liquid above the cabbage

7. To keep the cabbage submerged, fill a zip-loc bag with water and salt and rest it on top of the cabbage to keep it below water. If it’s not kept under the saltwater, you risk the cabbage going mouldy

8. Leave your cabbage for about a week in a room-temperature environment, using the zip-loc back as the ‘lid’ until it’s ready

“There’s going to be lots of bubbles because the microbes make carbon dioxide at first and then they make lactic acid which is kind of like a natural vinegar,” Caroline explains. “And that makes the ferment safe because nasty bacteria don’t like salt and they don’t like vinegar.”

After about a week when you’re happy with the outcome of your saurkraut, store it in the fridge. Caroline explains that the taste of your sauerkraut will be at its best within the first 2 months of storing it but that it will last, and have the same health benefits, for 6 months.

You can use this method with any other vegetable although some vegetables will take longer than others to ferment. 

Caroline has a full guide to fermenting vegetables with salt tables over on her website to help you with your salt percentages; and she has also published a book all about fermentation if you’re looking for more information.

In many parts of the world, fermentation is part of everyday life, Caroline explains. “In the UK, we’re not used to live foods so that scares us because it’s something that we don’t know about.”

It is crucial to make sure that your fermentation process is safe otherwise you could be putting yourself at risk of salmonella, although this is fairly rare from eating fermented foods. Caroline has six basic rules you can follow to ensure you are fermenting foods at home safely:

1. If you are fermenting vegetables, make sure your vegetables are clean, unbruised and undamaged to avoid pathogenic bacteria
2. Taste your vegetables before fermenting - if it tastes unpleasant before fermenting it, it won’t taste any better afterwards
3. Use fresh vegetables - these have the best microbes
4. Don’t use oil in your ferments because nasty microbes can grow in this environment
5. Ensure all of your equipment and surfaces are clean - there should be no pets around
6. Remove as much oxygen as possible from the jar you use for fermentation

If you don’t follow these rules, mould could grow on your ferment. Some people say that certain kinds of mould are okay to eat but Caroline suggests avoiding eating any mould because it’s not worth the risk.

It is also advisable to incorporate fermented foods and drinks into your diet gradually, to avoid bloating and digestive issues.

Want to learn more about fermentation? Head to Every Good Thing’s website or read more about the benefits of fermented foods on Stylist.co.uk.