How to make fermented chilli sauce at home (just chillies, salt and time)

Every summer there's a moment, usually somewhere between the first proper braai and the first heatwave, when the chillies in the garden (or the bargain bag at the market) get completely out of hand. You can only eat so many. You could freeze them, sure. Or you could do what we do: chuck them in a jar of salty water, forget about them for a week or two, and end up with the best hot sauce you've ever had.

Fermented chilli sauce tastes nothing like the sharp, vinegary stuff from the shop. It's rounder and fruitier, with a gentle tang that builds instead of stinging. And the best bit is that the good bacteria do nearly all the work. Your job is mostly to chop, salt and wait.

Why ferment chillies instead of just blending them?

When you submerge chillies in brine, the lactic acid bacteria that already live on their skins start eating the natural sugars and turning them into lactic acid. That acid is what gives fermented sauce its tang and what keeps it safe and shelf-stable in the fridge. Along the way it softens the harsh, raw heat and pulls out all sorts of sweet, almost smoky notes. Same idea as sauerkraut, just spicier. If you've already made our first sauerkraut, you'll feel right at home.

What you'll need

• About 500 g of fresh chillies. Mix them up: a few hot ones (bird's eye, habanero, peri-peri) and some milder ones (jalapeño, red serrano, even a red pepper) for body and colour
• 4 to 6 cloves of garlic, and anything else you fancy: a carrot, half an onion, a thumb of ginger, a strip of lemon peel
• Non-iodised salt, like coarse sea salt. Iodised table salt can slow the bacteria down
• Clean, non-chlorinated water. If your tap water smells like a swimming pool, boil it and let it cool, or use filtered water
• A wide-mouth jar with a way to let gas out and keep air away. Our Vegetable Fermentation Kit has the jar, fermentation lid and glass weight sorted in one go
• Gloves. Seriously. Trust us on this one, especially before you rub your eyes

Step 1: Make your brine

For a 1 litre jar, dissolve 20 to 25 g of salt in 1 litre of water. That's roughly a 2 to 2.5% brine, which is salty enough to keep the bad stuff out but not so salty that the good bacteria give up. Stir until the water is clear again.

Step 2: Prep and pack

Pop your gloves on and pull the stalks off the chillies. Slice them roughly in half, or into thick rings for big ones. You don't need to be neat because it's all getting blended later. Keep the seeds if you want serious heat, scrape some out if you want it friendlier for the whole family.

Peel the garlic and slice any extras. Pack everything into the jar fairly snugly, leaving about 3 to 4 cm of space at the top. Pour the brine over until everything is covered.

Step 3: Keep it all under the brine

This is the one rule that really matters. Anything poking out above the brine is exposed to air, and that's where mould likes to start. Chillies float, so they need something holding them down.

A heavy glass fermentation weight on top does the trick. Then fit a fermentation lid or an airlock with bung so the gas the bacteria make can escape without letting fresh air back in. No burping jars every day, no surprise fizzing explosions.

Step 4: Wait (the hard part)

Put the jar somewhere out of direct sun. A cupboard is perfect. Pop a plate underneath, because brine sometimes bubbles over in the first few days.

Here's roughly what to expect:

• Day 1 to 3: Not much seems to happen. The brine might start going a little cloudy.
• Day 3 to 7: Bubbles! The brine gets cloudier and the chillies fade from bright to a slightly duller colour. That's all good news.
• Day 7 to 14: It smells pleasantly sour and spicy. Have a little taste of the brine. When it's tangy enough for you, it's ready.

In a hot South African summer things move quickly, and a week is often plenty. In cooler months, give it two weeks or even longer. There's no wrong answer, only how tangy you like it.

Step 5: Blend it into sauce

Strain the chillies and garlic, but keep the brine. Tip the solids into a blender with about half a cup of the brine and blitz. Keep adding brine a splash at a time until you get the thickness you like. Some people stop at a chunky, spoonable paste. Others go all the way to a pourable sauce and push it through a fine strainer.

A few ways to make it your own:

• A tablespoon of honey or a few chunks of mango or pineapple for a sweet-hot braai sauce
• A squeeze of lemon or lime for brightness
• A splash of apple cider vinegar if you want a sharper, more classic hot sauce bite and a little extra shelf life
• Smoked paprika if you're missing that smoky flavour

Is it safe? Check the acidity

A properly fermented chilli sauce is naturally acidic, and that's what keeps it safe. If you want peace of mind, dip a pH indicator strip into the finished sauce. You're looking for a reading of about 4 or lower. Most well-fermented batches land somewhere around 3.5.

Bottle it in clean jars or bottles and keep it in the fridge. It'll keep happily for months, and the flavour keeps getting better for the first few weeks.

Help, something looks weird

• A thin, white, flat film on top: That's usually kahm yeast. It's harmless but can taste a bit off. Skim it off, make sure everything is under the brine, and carry on.
• Fuzzy spots that are green, blue, black or pink: That's mould. Don't try to rescue it. Toss the batch, wash everything well and start again, making sure nothing sits above the brine next time.
• It's not bubbling: Give it time, especially if your kitchen is cool. Also check you used non-iodised salt and non-chlorinated water.
• It's way too salty: Blend with less brine and add a little water, fruit or vinegar instead.

Want to go bigger?

Once you've had homemade hot sauce, it's hard to go back. If you find yourself making it in big batches for friends (it happens to everyone), a 3 L fermenting crock lets you ferment a whole market haul at once.

So next time the chillies take over, don't panic. Grab a jar, some salt and a bit of patience. Your braai will thank you.

Get the Vegetable Fermentation Kit and start your first batch