The theory is simple: fruit and vegetables (and grains and milk, but fermenting those is more complex) contain natural bacteria which, when deprived of air, can inhibit the growth of microbes that would otherwise spoil them. They do this by converting the carbohydrates and sugars in the food to an acid, in which pathogens and other microbes struggle to thrive.
This gives fermented foods and drink their distinctive tang, as well as the famed probiotic qualities fuelling their popularity. Yet buying them isn’t cheap; at Ocado, for example, a 250g tub of kimchi costs £5.
Fermenting at home, however, is fun, easy and has minimal start-up costs. Most of the “ingredients” are already to hand, so long as you have a knife, fresh fruit or vegetables, a jar, sugar and/or salt. Here’s all the kit you need to get going – and the things you shouldn’t waste your money on.
Salt
“The salt should be high quality, and preservative free,” says Mark Diacono, author of Ferment From Scratch. “Otherwise those preservatives are acting against the bacteria you want to proliferate.” Try Maldon salt (£2.70, tesco.com) or Himalayan Pink Salt (£1.99, aldi.co.uk), but any high quality, preservative-free rock or sea salt will suffice.
Jars
The jars in which your fruit or vegetables will ferment should ideally be strong enough to withstand pressure that builds as carbon dioxide is released. You can use glass jars if you want to ferment on a small scale or are just starting out.
“I like using old Bold Bean Co jars to do smaller ferments quickly because they’re big and sturdy. If you have a tight budget or are experimenting, use any recycled jars,” says Ukrainian chef and food writer Olia Hercules, who regularly hosts fermentation classes. Remember to unscrew the jars regularly to release the gases, or you’ll have a mess on your hands.
Kilner jars (£4.50, ocado.com) withstand the pressure better, come in a range of sizes and often with lids attached. If you feel there is enough going on in your life without remembering to burp the kimchi, you can even buy a valve to screw on to the Kilner, “so you don’t have to worry about burping it at all”.
Weights
The most important thing, when fermenting food, is that no air can get in. This means using a jar with an airtight seal but also ensuring that whatever is being fermented is always submerged beneath the brine. You can use any home-fashioned weight here, so long as it’s sterile – Diacono uses freezer bags filled with water – but for peace of mind, he recommends “pickle pebbles” (£9.99, happykombucha.co.uk): “glass disks that fit perfectly within the jar, and push down the sauerkraut or pickled cucumber you’ve made”.
The need to keep the vegetables submerged and the brine occasionally topped up is the reason Jefferson steers clear of Crockpots. “You have to keep checking the water seal, and you can’t really see what’s going on – less of a concern when it’s all glass.”
Muslin and sieve
Fermented drinks are different, however; kombucha, tepache and the like need air in order to ferment. For these, you will need (in addition to your jar) some muslin (£3.50, happykombucha.co.uk), a sieve (£9.99, lakeland.co.uk), and some glass bottles which can withstand high pressure; Diacono sources from Kilner or similar glass flip-top bottles (£3.82, nisbets.co.uk). The muslin sits over the jar while the fruit (or tea, in kombucha’s case) is fermenting, before it is strained into the bottle ready to serve.
Things you don’t need
There are some things you think you may need, but which you don’t really – at least not when starting out. A mandolin is one of them. Food writer and author of Your Daily Veg, Joe Woodhouse, says he likes his Bron Coucke stainless steel mandolin because it has lasted 20 years, and “you can get everything into the same shape, so it’s fermenting at the same rate – and it feels chef-y”, he says – but neither he nor anyone else feels they’re necessary. A sharp knife will suffice; fermentation enthusiast and co-founder of online farmers’ market, Wylde Market, Nick Jefferson recommends Robert Welch for affordable quality.
Sterilisation equipment and products are not just unnecessary; they are counter productive. The kit you use should be clean, but not sterile. You just need a dishwasher or hot, soapy water, says Hercules. A fermentation recipe book might be nice to hold your hand in the early days – as well as his own, Diacono suggests James Read’s Of Cabbages and Kimchi – but there are plenty of online guides. Try Doug McMaster’s Zero Waste Cooking School, BBC Good Food or the Zoe beginner’s guide to fermentation. Jefferson learned a lot from It’s Alive With Brad.
Last but not least, you’ll need a fridge to store and maintain your ferments when they’re ready to devour.
