A beginner’s guide to fermentation: ‘After two days it smelt distinctly cheesy, but better at least than the dead-badger smell I was expecting’

From sauerkraut and kombucha fruit leather to pickled plums and honey marmalade, the art of fermentation is one well worth learning, advocates lifelong forager John Wright.

I have long paddled in the shallower waters of fermentation, making beer, homemade wines of variable drinkability, real ginger beer, yoghurt and blackberry vinegar, but the deeper waters of kombucha, jun, kefir, sauerkraut and half a dozen other exotica were places I never dared enter. These latter all seemed to possess a strong element of witchcraft and gifts of various concoctions from enthusiastic friends had not made a favourable impression.

Diffident as I was, I never attempted to replicate their offerings. Until now.

My friend Rachel de Thample had sent me an early copy of her Fermentation: River Cottage Handbook No 18 and invited me to view her collection of ‘Lizard’s legs, and howlet’s wings’. After hearing what she had to say and seeing and tasting what she had made, I returned with a few jars of festering ‘starters’ to try it for myself.

Attempt 1 — Kombucha and kefir: ‘It’s started fizzing furiuously, and tastes overwhelmingly of butter’

Together with the excitement of embarking on a fresh project, I experienced anew the sense of responsibility I had felt years ago, when a friend sent me some of his precious ginger-beer ‘plant’ or ‘starter’. It thrived under my close attentions for several weeks and then, after a fit of care-fatigue on my part, it died. I asked him if he could send me another one, but he refused — rather rudely, I thought. It was as if I had agreed to feed his guinea pigs for two weeks when he was away and forgotten to do so.

That ginger-beer ‘plant’ was no plant, of course. It was, instead, a bizarre congregation of micro-organisms — both yeasts and bacteria — that ferment the sugar into a variety of organic compounds. In the case of ginger beer and kefir, it comes in the form of small, whitish rubbery granules; with kombucha, it’s a solid lump of rubber, although the one Rachel gave me looked like an opened oyster that had been left in the sun for a day or two. These congregations (more properly ‘consortia’) are types of ‘biofilm’, in these cases a ‘symbiotic culture of bacteria and yeast’ known by the homely acronym of ‘scoby’. The rubbery nature of scoby is due to a mat of cellulose produced by the bacteria.

Is a shelf really a shelf unless it has some home-made Kombucha on it? (Okay, probably it is.)

Biofilms abound in the natural world, with large structures such as the layered mats of cyanobacteria known as ‘stromatolites’, the layer of helpful bacteria that encompasses plant roots known as the ‘rhizosphere’ and (you will not thank me for this) dental plaque.

The upshot is that you make a sugar solution flavoured with ginger for the beer or tea for kombucha, add the appropriate scoby and a little of a previous batch, cover the jar with a muslin cloth (to let in air, but not flies) and leave it to ferment. If you strain and bottle it when it still contains sugar, it will be fizzy. The yeasts produce alcohol, which is mostly converted to lactic and acetic acids by the bacteria, and endless flavour chemicals are also created.

During the process, another scoby will form as a disc on top of kombucha and the one you added as a starter will have grown. You now face the anxiety of dealing with this nascent population explosion. I have called on friends to adopt one, but without success.

Most will know what ginger beer tastes like, but what of kombucha? Well, it does have some interesting and complex flavours, but is too vinegary for my unrefined palate. Nevertheless, I console myself with the fact that it is very good for my gut microbiome and drink it anyway.

At the moment, I have a water kefir on the go. This sat sullenly for a few days, but has now started fizzing furiously. Unfortunately, it tastes overwhelmingly of butter, indicating that diacetyl has been produced — a problem I have encountered in making wine. With luck, my attempt to aerate it with a whisk will solve the problem. Things do go wrong, but these are robust organisms and recovery is usually possible.

The Kefir process is susceptible to a few hiccups…

Attempt 2 — Sauerkraut: ‘The brine appeared miraculously during the energetic squeezing’

One of my great successes, courtesy of Rachel’s tuition, is sauerkraut. I finely shredded a cabbage and sprinkled it with 2% salt. This was meant to produce enough brine (by osmosis) to cover the cabbage once it was pressed into the Kilner jar, but, after the required salting time, it was barely wet. However, the brine appeared miraculously during the energetic squeezing of the vast amount of cabbage into my small Kilner jar.

Sauerkraut requires no starter, relying instead on the lactic-acid bacteria that exist on the cabbage, the small amount of salt used allowing these bacteria species to predominate. It is now two weeks old and already a pleasant revelation in that it is, despite my forebodings, unmistakably sauerkraut.

Pomegranate-molasses-glazed roasted duck breast with homemade sauerkraut

Now you’v made sauerkraut, you can make pomegranate-molasses-glazed roasted duck breast with homemade sauerkraut, following Melanie Johnson’s recipe.The Kefir process is susceptible to a few hiccups…

Attempt 3 — Sourdough: ‘It appears to be impervious to heat. The texture is that of Kevlar, so it is bullet-proof, too’

Rachel is endlessly inventive with her recipes: kombucha fruit leather, pickled plums, fermented wild mushrooms, fermented honey marmalade and dozens more, covering every fermentation method.

The one I was truly dreading, however, was sourdough. It was not the sour taste of the bread, nor facing the long process involved that I feared, it was the culture that seems to surround it. In the foodie circles within which I sometimes rotate, making sourdough is a must. Anyone who has not made it is treated with a degree of pity and looked down upon as unworthy. Well, they won’t be looking down on me anymore — I will be looking down on others. ‘Really? You’ve never made sourdough? How quaint.’

I will not bore you with the entire process, but I do advise you to set aside a week to make it. To be honest, only the final day requires your undivided attention. My final day ended up being two final days because I got the timings wrong, so do pay close attention to the recipe and mark off the stages as you go. I made my own starter using 50g each of water and bread flour mixed together, covered with muslin and left for a day. The next day, I stirred in the same amounts and continued to do this for a few days more.

The idea here is that lactic-acid bacteria and yeasts that are present in the flour and air will ferment in the moist conditions.

It should smell slightly alcoholic and yeasty, but mine smelled distinctly cheesy after two days, which was, at least, better than the dead-badger smell I was expecting. Fortunately, the good guys of the microbial world seized the upper hand and it was much sweeter by the following day.

Homemade sourdough bread.

Once my starter was mature, there were hours of adding flour, folding, proving and then baking. Eventually, a near-perfect loaf was born, looking and tasting exactly like the stuff you get in smart restaurants. I enjoyed sardines on sourdough toast and had some with my tomato soup. It is very nice toasted, but takes twice as long as usual, as it appears to be impervious to heat. The texture is that of Kevlar, so it is bullet-proof, too. Still, I liked it — even the sourness — and am very proud.

The Future

I shall continue my explorations of fermentation armed with a renewed enthusiasm. I asked Rachel if you could use a scoby to make sourdough bread. She said that you could, leaving me with the joyous prospect of making scoby dough.

‘Fermentation: River Cottage Handbook No. 18’ by Rachel de Thample is published by Bloomsbury (£11.99)