A Treatise on Fermentation

I asked the question below on a recent Instagram post, and had lots of interesting replies – it's grown into a mammoth article but you can scroll down to comment if it's all too much.


"Do you ferment for…..HEALTH, FLAVOUR, FUN, SUSTAINABILITY, PRESERVATION, TRADITION, SELF SUFFICIENCY?   ..Not sure or not got started yet? 

Food Fermentation - A Definition:

Food fermentation is a controlled process where microbes utilise a food source to produce a range of useful end products which can preserve and enhance food and make new flavours.  There are several different types of fermentation; lactic acid, koji-based enzymatic, vinegar, wine, alkaline – the microbes involved may differ, but they’re all examples of humankind’s incredible ability to manipulate food to its advantage over the past 10,000 years.

Fermenting for HEALTH

When microbes are given a source of food they use it to nourish themselves, just like we do – but without the chewing. They release enzymes that help them break down the food, producing organic acids, vitamins, more enzymes, and lots of other phtyochemicals (plant compounds) that can nourish you and your own gut microbes.  So fermented foods are nearly always more nutrient rich than their non-fermented equivalents.  The other thing that happens during fermentation is that the microbes grow into huge populations – we know that these microbes  (with names like Lactobacillus sp, Bifidobacterium sp, Sacchromyces boulardii) are excellent at improving the state of our own guts as they pass through – helping good microbes to grow, supressing less helpful ones, making short chain fatty acids to help your gut lining strong and healthy, stimulating your immune system.  And whilst this goes on, all you have to do is get into the regular routine of munching a spoonful of (sauer)kraut, or drinking some kefir kvass or kombucha!  As a kimchi college student recently summarised, she tries to have “ one of the Ks every day” – good advice I think!


Fermenting for FLAVOUR

The end results of microbes fermenting complex substrates are foods with altered flavours and textures that just can’t be recreated without them.  Think of  kimchi with its unmistakable aroma ( or odour if you’re not a fan) or that sulphorous kick you get when you open a jar of sauerkraut. There’s an acidic tartness that’s definitely related to vinegar, but gentler, more sophisticated than your average pickled onion. There’s a lot of lactic acid for sure, but also tens of different flavour compounds, including other acids, esters, phenolic compounds, alcohols and it’s all made by microbes. 

 Samin Nosrat in her recent book & netflix series identified that Salt Fat Acid Heat are the four basic factors that will define how good your food will taste.  Vegetable ferments  – especially tick half these boxes – in addition to their roles in making the fermentation process safe, salt enhances flavour and acid brightens and balances.  You’ve probably heard Big Greg or Marcus Waring on Masterchef, constantly in search of that “acidity” in a dish.

Perhaps that’s why “sauerkraut goes with everything” isn’t as ridiculous as it may first sound.  Kimchi and sauerkraut can brighten almost every meal.  Don’t be afraid to cook with them, too.  Although this will reduce the number of alive microbes, it can introduce yet another range of flavours – cooked kimchi tastes rich and umami-ish, and loses its rather obvious cold identity. The histories of Eastern European and Korean cooking are filled with cooked fermented food recipes.  

NOMA restaurant in Copenhagen have done more than anyone in recent years to promote the idea of fermenting for flavour rather than for health.  Their recipes really take normal fermentation techniques to the very edge, and show that there’s still a world of undiscovered flavour out there – their book includes delicacies such as lacto- fermented blueberries, barley miso and yeast garum ( which tastes almost exactly like home made marmite!).

If you’re fermenting for flavour, no holds barred, just go for it, as long as you follow the basic principles for safe fermentation, and accept that sometimes you might make something horrible (my fermented kale and butternut squash springs to mind), but it’s all information that you can apply next time – take notes too!


Fermenting for FUN


From a tiny jar of kefir grains to a shop full of ferments – how did that happen?!  whilst most people don’t end up with an actual fermentary like I’ve done lots of people do end up with a fermentation shelf.  Once you become aware of what those microbes can do, watching and waiting for that transformation can become a serious hobby.  The anticipation when a long-awaited batch of chilli sauce has reached its testing date, the satisfaction of a completely smooth, shiny set milk kefir after a mere 24 hours, the 36 hour transfomation of soya beans into a cake of tempeh, or the wonder of red cabbage as pH indicator whereby its change from violet to puce indicates that the pH has dropped and fermentation is well under way – what’s not to love. Then there’s the kit. There’s all sorts of kit available if you like new shiny toys for your hobby, and at the other end of the spectrum, no shortage of ideas about how to ferment any and everything in the most creative and inexpensive ways possible. 

Many people, me included, find relaxation in preparing veggies, and the satisfaction of legitimately being able to plunge bare hands into a vat of cabbage and squeeze cannot be underestimated.  The squish of kimchi through ones' fingers has to be experienced to become something wonderful as opposed to downright disgusting!  Don’t think twice about getting the rest of the family involved either – maintaining a water kefir “pet” is a great gateway to fermentation, or having a good old bash of some cabbage can be fun even for little hands.   Though of course you can’t get all of the people all of the time.  My very own husband, though he’s happy to drink the stuff, has so little interest in maintaining our own keifr at home that he’s put the grains through the dishwasher - Twice! 



There’s no doubt that home fermentation has a role to play in both reducing waste and reducing the number of industrialised processes our food has to go through.

Let’s compare milk kefir made at home or milk kefir bought from the supermarket.


I purchase some grains or inherit from a friend.  I get some milk (up to you if you’re filling up reusable bottles from Better Food or getting a doorstep delivery, then that’s extra points!), put in a reusable clean jar and leave on the side till set.  I strain, fridge the kefir and start again, washing out the jar if I’m feeling conscientious.

Shop kefir:

The milk is delivered by road to the kefir factory.  It then undergoes a series of large-scale production steps involving vast vats and lots of stirring. The kefir is then put inside little plastic bottles and transferred to refrigerated lorries where it is transported to the shops.  Where it sits in an open refrigerated cabinet until you go and buy it.  When you get home you drink the kefir and recycle the plastic bottle in which it came.  This gets transported to recycling depot and energy is used to make it into something else.

Homemade wins every time.

Fermentation, especially of vegetables, has another role in terms of sustainability.  As we will see below, fermentation has been used for preservation for centuries, and can help to reduce food waste by prolonging the life of fresh produce, not indefinitely for sure, but for weeks or months even.  

 Fermenting for… PRESERVATION

Humans have been preserving food for a very long time, tens of thousands of years at least, using different methods according to their environments, their value having been realised by observation – you’d preserve by drying if you lived in the Saharan sun, by freezing if you lived in the Artic Circle.  If you lived near a great salt lake you’d have worked out its preserving qualities upon fish, and there’s evidence that salt trading was up and running around 6000 B.C. in China. Grapes could become wine and then vinegar – wine deposits have been found in jars that are over 10,000 years old.  Yoghurt is thought to have existed from at least 5000 B.C – probably not rocket science to have worked out that souring milk in a controlled way was a very tasty method of preserving it.  And so eventually, somewhere in Northern China, it became known that cabbage could be preserved and become nutritionally enhanced by mixing it with salt. In fact, sauerkraut and rice were used to sustain the workers building the Great Wall of China throughout the harsh winters in the 1st millennium B.C.  

But what about nowadays when we have fridges, freezers, canning, pasteurisation, vinegar pickling at our disposal, why choose fermentation? The primary reason is because none of the above are full of live microbes that can be good for your health, nor are any of the above more nutritious after processing.   This is especially relevant if you’re growing your own veggies and can be a useful way of using up some surplus.  But it’s not the answer to everything – many ferments are best eaten within 4 or 5 months – after that time the number of lactic acid bacteria ( the most useful species for us humans) can begin to decrease and ferments might beome a bit mushy.  Some won’t last that long anyway. Fermented courgettes are delicious but have a relatively short life span – same for tomatoes and peppers. Cabbage based ferments, especially red, white and savoy usually maintain their texture for the longest time. After a few months in the fridge, as the number of helpful bacteria start to decrease, an opened jar can become a target for contaminating microbes, so check for surface growth before digging in.  With regard to kimchi, Kimchi Jigae is a Korean stew (usually pork based), where the use of old “ripe” , sour kimchi is a key ingredient.  Aged kimchi, 1 year plus, even has a special name; Mook eun ji, and is regarded as a speciality, as it can develop a richer, extra savoury taste. If you’re leaving your kimchi for a year, best to keep an unopened jar for this.  Other ferments that last a long time are chilli sauces, although they must be kept at the back of the fridge, or continued yeast action ( there are usually yeasts present on fruit that is often included), can lead to alcohol production eventually and not in a good way!  Miso, especially “red” misos, which have a higher salt content, can be kept for several years, as can preserved lemons or other citrus – they will become brown and soft, but still retain their flavour.

Fermenting for TRADITION

Interestingly, apart from a brief brush with sauerkraut for sailors on board one of Captain Cook’s voyages, we have very little history of vegetable fermentation here.  Cheese, yes, but veggies were often chutneyed to preserve them – with lots of sugar and vinegar.  In fact these days, even though home canning is massively popular in the states, it’s hardly ever done here.  We really do like to have things done for us don’t we? That said, I’ve had several customers in the shop who remember ginger beer plants from when they were children, or kombucha scobies in the 70s or mum making yoghurt in the airing cupboard, so for some of us these are traditions that we can carry on – for others of us – me included, it’s about starting some new ones.  Even though I am from an Ashkenazi Jewish background, not a fermented vegetable passed my lips till I was well into my 40s.  But here in the UK where we are affluent, busy, distracted ( which leads to a certain kitchen laziness without us actually being LAZY generally), where no matter what your price bracket you can can eat all kinds of rubbish at the drop of a hat, what price progress eh? Our food is less nutritious and more mucked about with than ever before.  There’s always some enormous conglomerate keen to persuade you that their “protein bar” is better for you than real food.  It isn’t.  Progress isn’t always better sometimes it’s just different. I don’t want to sound like an evangelical nutter, but why not join me on my crusade to do things differently?  Important to remember, I think, that if you’ve got children show them, teach them, involve them ( I’m thinking of the younger variety rather than the sulky teen, but might be worth a try!)



Lockdown and Brexit have brought strange circumstances to our shores.  For the first time certainly in my memory, “you can’t always get what you want” ( in the words of Mick Jagger)  became a thing.  Loo Roll, Pasta, Flour, Tinned Tomatoes, Beans, things that we took utterly for granted just weren’t there when we needed them.  With a lot more time on our hands, many of us turned to “making our own” bread and pasta, growing vegetables, discovering new skills or honing old ones. As life gets back to normal, we’re falling back into our old habits of being looked after in every regard, but perhaps this should have awoken us to the concept that things can go wrong – so being aware of how to do these things yourself, even if you don’t always do them could be a good idea.

It’s not rocket science to point out that fermented veggies rock in a something like £20 per kilo.  You can buy a LOT of vegetables for £20.  Hand made milk kefir retails at about £10-12/litre – you can buy and awful lot of milk for a tenner.  So there are definitely financial advantages to be had by taking the plunge and doing it yourself.  But don’t always do it yourself or I will go out of business!

So after all that, what kind of fermenter are you? What’s driven your interest ? I’d be very interested to find out, let me know below…


1 comment

  • I’m just getting started but loving the sustainability and self sufficiency angles – I got your book for Christmas, it’s really helpful!

    Elise Grover

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