Bread with Wild Kiwi Yeast (A Failure)

Bread raised with wild kiwi yeast

Until now I had baked nothing but sourdough, drawn to its simplicity — but suddenly I wanted to try raising a culture from something else.

The fruit I chose was kiwi. You hear plenty about raisin cultures, but I had no raisins to hand and a great many kiwis, so kiwi it was.

Step 1 — Raising a culture from kiwi

What you need:

• Kiwi 1
• Water200cc
• Storage container

First I have to generate the yeast that will lift the bread. The microbes living on the fruit feed on the fruit's own sugars, breaking them down and multiplying — so add water, stir, and leave it, and a culture should raise itself.

The thing to watch is that organisms other than the ones you want do not multiply while the culture establishes itself. So start by sterilising the jar in boiling water.

Cut one kiwi into rough pieces, put them in a jar, and pour in 200cc of water.

Step 2 — Observation (and waiting)

For now, stir it thoroughly once a day to supply oxygen, and watch. The things to watch are bubbling and smell. Yeasts give off carbon dioxide as they break down sugars, so if they are active you should see bubbles. And smell is what tells you whether unwanted organisms are multiplying. If the yeasts you want for bread are establishing themselves, it should smell like a sweet wine. If it turns unpleasant, like something rotting, it is finished.

From day one to day three, the bubbles I expected did not appear, and the water gradually turned cloudy. I smelled it nervously — but it was that slightly sweet, wine-like smell, so I kept stirring and waiting. It never bubbled vigorously the way I had imagined.

From day four I was busy and could not watch the kiwi closely. Fine bubbles had increased, and the pieces of fruit had risen to the surface. Fruit floating presumably means the sugars have broken down and the mass has lightened, so I had the jar put in the fridge to slow fermentation.

Step 3 — Building a leaven

What you need:

• The culture from step 230cc
• Bread flour30g
• Storage container

Home from a work trip, I checked the kiwi culture: small bubbles on the surface. I prepared a second jar, separate from the one used up to step 2, and sterilised it. Then 30g of bread flour and 30cc of what I take to be the culture went into the jar, and I mixed it well.

With sourdough you see no change for a while after feeding, but the kiwi culture seems to ferment faster: bubbles appeared fairly soon after the culture and flour were mixed. The smell was sweeter than sourdough — good, I thought, still hopeful at this point.

But after watching for about six hours, although bubbles appeared in the leaven, it did not rise at all. Each time I stirred it, it grew smoother, until eventually it was a runny, almost liquid thing. Looking it up: kiwi apparently has powerful enzymes that break proteins down aggressively. Those enzymes go after the gluten that matters for bread, too. So that is why it turned to liquid...

But I am not giving up yet. Bubbles mean the yeasts are fermenting and carbon dioxide is genuinely being produced. If I can trap that carbon dioxide, the bread should rise.

Step 4 — Cultivating the leaven

What you need:

• 30g of the leaven from step 3
• Bread flour30g
• Water25cc
• Storage container

What I want is as little as possible of the enzyme causing the liquefaction, and as much as possible of the yeast producing the bubbles. So I discarded half of the runny leaven from step 3, added bread flour and slightly less water than flour, and stirred well. Willing the yeasts to multiply, I left it overnight — and by morning the leaven had risen considerably. Stirring it a little, there were bubbles through the middle and a web of strands. This looked like something I could bake with.

Step 5 — Making the kiwi-yeast dough

Ingredients:

• 60g of the leaven from step 4
• Bread flour250g
• Water165cc

Add 60g of the step 4 leaven to 165cc of water and stir gently until fully dissolved. Add 250g of bread flour, mixing first with the scraper, turning it up from the bottom; once it is roughly together, use your hands to bring it into one mass. After that I did three rounds of fermenting and stretch and folds.

For the details of shaping, see

How to bake a basic sourdough loaf

and similar articles.

Step 6 — Baking the kiwi-yeast bread

Exactly as when baking an ordinary sourdough loaf,

1. Put the Dutch oven in the oven and preheat to 250°C.

2. Once it is up to temperature, turn the dough out of the basket onto a sheet of baking paper.

3. Score the top with the razor.

4. Take out the Dutch oven, lower the dough in on its paper, put the lid on, and bake at 230°C for 25 minutes.

5. Take the lid off and bake at 240°C for a further 10 minutes.

That was the method — but the score would not open and it never rose fully. Again, presumably the kiwi enzymes weakened the gluten and the dough went slack. Hmm. Either more research into kiwi cultures, or try a different fruit. Either way, I want to have another go at baking with a fruit-raised culture.