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Fermented food. A few short years ago nobody in the general population would know what you’re talking about. Except for a few sauerkraut fans, perhaps, or those who've worked with speciality foods for a living. But so many of the things we eat are fermented, especially those we really like, that, amazingly, we haven’t been swamped by the term.
Coffee, tea, vanilla; they’re all fermented. The great taste in aged cheese? Partly to do with fermentation. Soy sauce, shrimp paste, kimchi? Fermented. Not to mention beer and wine and cider and all the kinds of vinegar under the sun. Even a properly aged salami or prosciutto has gone through a fermentation stage.
So what is fermentation? It’s a chemical process, kick-started by bacteria and yeasts, that alters the composition, and flavour, of food. Discovered presumably by accident, it’s a managed decay of food that has allowed the ingredient to be preserved well after its harvest. Essentially you’re producing lactic acid, or perhaps ethanol (alcohol), and acetic acid. Yoghurt, for example, is fermented but not alcoholic, because you only aim to get lactic acid production. With wine, you ferment the sugars to get alcohol.
Good fermentation preserves and alters much of the nutritional quality, too, and can even enhance it. You can ferment cabbage or carrots, cucumbers or zucchini. Even olives must go through a fermentation stage to turn from truly disgusting to eat, to sublime.
Most home fermentation is about vegetables. And much of that involves variations on kimchi and sauerkraut. Fermenting vegetables is done using salt, which slows the action of bacteria and yeasts down, helps avoid mould, and adds flavour. Generally, the questions revolve around the quantity of salt, and this can be a bit hard to be specific about. It does depend on your climate, your palate, your cabbage. Get Matthew's sauerkraut recipe here.
A lot of fermentation works best at 1-2 per cent brine. That’s about 1 tbsp of coarse ground salt per 500 ml of water at most. This kind of pickling is vastly different from pickling using just a vinegar. It’s more likely to go wrong, but it’s also possible to get things with a way more interesting flavour.
The thing to remember about fermenting is that you’re dealing with living food. The bacteria and yeasts that ferment your food need certain conditions to thrive. They need moisture, they need warmth, and they need something to eat. That’s why you feed your sourdough starter with a little flour and water regularly. That’s why you try to keep your kombucha at 25°C or so. That’s why too much heat will kill the bugs that do the work for you. As can neglect. Too much salt can slow or even prevent fermentation.
Most good fermentation is helped by adding a living culture. A SCOBY is an acronym for 'symbiotic culture of bacteria and yeast', is essential for making kombucha. It’s best to get a SCOBY from someone else - the same for when making vinegar. The ‘mother’, the cloudy, almost slimy bit you may get in a live vinegar, is the special part that you can use to inoculate some old wine or cider to make your own vinegar and a SCOBY is just a solid, specialised mother.
With yoghurt, you can start with the bacteria in a store-bought natural yoghurt – just look for the term ‘live cultures’ or ‘live bacteria’ on the label. You can use the runny bit that comes off a pot-set natural yoghurt in your sauerkraut because that contains the same lactic acid-producing bacteria that you want to transform simple pounded cabbage into something totally delicious to put on your pastrami sandwich. And while cabbage already probably has those bacteria on it, a little-added culture doesn’t hurt.
For some things, like making sourdough or kombucha, you can harness all the native bacteria and yeasts in the air quite safely, though every type of fermentation is different and needs some reading and practice. The bacteria you want to pickle vegetables are usually in and on the vegetables, but a little help from an existing live culture doesn’t hurt. For dairy products and meat, it’s best to add culture that is made commercially to avoid any of the bad bugs that can thrive in the same conditions as all those good bugs.
Pickling and fermentation are ancient tools. They’re particularly useful to gardeners, or those who live seasonally and hate waste. Many aren’t particularly time-consuming, and the results can be transformative. Inevitably you will have some failures when you attempt to ferment things at home. The possibilities, however, are enormous. The potential for far better-flavoured food, for a more interesting choice in your pantry, and for food that is as far from the homogenous norm as you can get, makes any effort worthwhile.