It’s easy to harvest wild yeast and to make your own yeast culture, for brewing or for baking, or to use in the wild for backwoodsman cooking. It might not perform quite as well as the super yeasts bred by specialists in expensive factories, but it’s the yeast our ancestors used for thousands of years, harvested from the wild.
Yeast occurs naturally, on everything, even on your skin, and also on the skins of most fruits (dried or fresh). Mead and wine makers of old did not add yeast but relied instead on the wild yeasts, those which were already living on the fruit, or floating around in the air. Many English cider makers today still allow fermentation to occur naturally, from the wild yeasts on apple skins.
I’m a beekeeper, and if you leave uncapped stores, or wet frames hanging around for a while then you can sometimes pick up the smell of fermentation beginning to take place. That’s why bees concentrate their gathered nectar down from 80% moisture content to 20% moisture, or less, to prevent fermentation taking place. Whilst mead is great for us it is fatal for the bees.
So wild yeasts are everywhere.
Can we use this yeast used for fermentation for baking?
Surplus yeast created by the beer brewing process, is known as ‘barm’, and was once commonly used by bakers for making ‘barm cakes’. It’s the yeast rich froth or scum which forms on top of fermenting beer or wine.
Barm cakes can still be bought in Lancashire though they are no longer made with barm, and so the name survives as simply a local name for a bread roll. There are recipes for barm cakes on the internet and they all involve bought, fast action yeast which means they aren’t made with barm and therefore aren’t true barm cakes. Up to a few years ago I knew of two independent makers of true barm cakes but they seem to have retired and so the tradition is lost, probably because the process requires skill and patience, two things modern society doesn’t value much.
So the same yeasts can be used for brewing or baking, one straight after the other if you like, as they used to do, all over the country.
How to Get Your Yeast
The first step is achieved by gathering fruit, either cultivated or wild. It’s best to use older fruit, even damaged, the stuff you would normally discard. Clean, perfect fruit has a smooth surface which can easily be washed by rain whereas older, less than perfect fruit will have wrinkles or breaks where yeast will gather and fermentation may have already begun on the ripe insides throughin breaks in the skin.
The last pick of the year with a mixture of good and sub standard fruit (normally discarded).
I’ve deliberately selected the older, wrinkled or damaged gooseberries for wild yeast making.
Don’t use supermarket fruit because it may have been washed or polished clean, waxed, or sprayed with anti fungal chemicals, or with worse. You are after wild natural yeasts and these aren’t found in abundance in modern sterile growing conditions, or in the packaging centres of large scale production, in fact they are deliberately eliminated.
To make your starter yeast culture:
1 – Place the fruit (or herbs) in a jar up to about half full. Be sure not to wash the fruit, or to take the skin off, as this is where the yeasts will be. Sweet ripe fruits are best, (and even more important if you have no sugar or honey).
Use a large jar if you want to use some of the yeast soon, and if you also intend to keep the culture going for next time.
In my two examples below I have used rhubarb and gooseberries from my allotment.
2 – Add water, or weak sugar syrup until you are about three quarters of the way full.
Sugary water (syrup) goes into the gooseberries
Freshly sliced, but not washed, rhubarb in a jar, awaiting sugar.
3 – Add a couple of teaspoons of sugar or honey if you haven’t added syrup. It may work without a sweetener if the fruit is ripe, but it will be much faster and more vigorous with. Give the jar a shake to dissolve the sugar, no need if you added syrup. If you are a brewer or wine maker you will probably have yeast nutrient and you can add this now. You could also test the specific gravity and adjust accordingly.
4 – Put the lid loosely on the jar and leave in a warm place. If you screw down the lid the jar will explode. In as little as 24 hours bubbles may begin to form on the fruit. The bubbles indicate that the yeast is reacting with the ingredients in your mix, in other words it’s multiplying, making yeast (and alcohol).
Bubbles begin to form on the fruit after 24 hours
I usually give the jar a little shake now and then to hasten the transfer of yeast into the liquid. After 3 or 4 days a good amount of bubbles should start to appear and a froth may begin to gather on the surface, depending on the fruit you used.
The water will turn from clear to cloudy as the yeast multiplies.
Bubbles gather on the surface and the liquid begins to go cloudy
The same thing is happening here with the gooseberries on day 4. You can no longer see through the liquid and bubbles are rising from the liquid and are passing up through the fruit.
4 – Once you are sure that the yeast is living in the sugary water (usually after 3 or 4 days) then discard the solids and keep the liquid. If left in the jar the solids will disintegrate, turn to mush, and will be difficult to remove later, especially soft fruit like rhubarb.
Day 7 and the yeast water is even more cloudy but the fruit is colouring the water too. Time to get rid of the fruit.
Add another spoonful of sugar or honey to keep the yeast fed. The liquid will continue to go more milky, and fine foam may form on top as the yeast multiplies.
The fruit is removed and the jar topped up with sugar water to create enough yeast culture to experiment with.
5 – Once the liquid is milky and fermenting vigorously then you can use the yeast water for brewing, or in bread making (or other recipes).
Keep the fermentation going by the occasional addition of sugar or honey (honey contains more nutrients than sugar) and topping up with water. If left alone the yeast will eventually use up all the ingredients, and then die.
You can slow down the fermentation by keeping the culture somewhere cool.
If you have no immediate use for the yeast water, and the jar is full, you can keep the yeast vigorous by tipping half of it away and by adding more sugar or honey, and water, to keep the yeast fed and active. Or pour the mix into a bigger container and add more water and sugar.
This never ending fermenting process was once commonly used with sour dough for oatcakes in Britain, and was kept going in remote communities for years, possibly centuries, evolving over time, sometimes giving unique local tastes to oatcakes, which were loved by locals who grew up with them, but sometimes considered almost inedible by outsiders.
Testing your yeast
If you are an experienced brewer, or wine maker, then you should be able to tell from the smell or taste if things are going in the right direction, or just test the specific gravity again.
For bread making there’s only one way to find out and that’s to make some bread. Remember that wild yeast is not the super yeast you may be used to and things may take a little longer to get going. And just as brewers ‘barm’ yeast gave a distinctive flavour to barm cakes then your yeast may also contribute to the flavour, but there’s no telling how until you try it.
I am currently experimenting with the yeast culture I obtained from the red gooseberries and I will post the results here when I have them. I’ve experimented before but I didn’t take any pictures, and we all love a few pictures don’t we? I hope to try sour doughs, standard dough, and wine making. The wine making results may take a few months.
Experiment 1 – Rising test with sourdough
On day 6 I mixed a little of the yeasty liquid with plain flour to a batter like consistency, to create a type of sour dough. After 3 days the yeast activity was obvious so I carried out a simple test.
The bubbles form in the batter and gently rise to the surface
I subject a spoonful of the mix, unchanged, to gentle heat in a frying pan to see if it would rise during cooking, and it did.
A test sample to see how the mix reacts to gentle heat
So I turned on the oven and put a big spoonful in a hoop (to stop it spreading).
It rose nicely
Commercial yeasts are bred to give consistent bubbles whereas a collection of wild yeasts will give different bubble sizes producing interesting patterns and textures. The cross section below shows this. The flour culture needs more time to really get going but, for the yeast count to increase, but as you can see, after only a few days there are encouraging results.
When sliced open the bubbles are revealed
The liquid culture was topped up with sugar water, and continues to bubble away, gently increasing its yeast count, and I’ll be using it to make wine.
The sour dough culture was topped up with strong bread flour, and water, and left to build up the yeast count so that I could experiment with larger quantities.
Experiment 2 – Sourdough pan loaf
Once the sourdough culture was bubbling well I split it in two. The culture was topped up with strong white bread flour and water and left to continue bubbling.
The other half had flour added to it to increase the amount and was left to rise in a jug for a day.
More flour was then added to make quite a soft dough which was kneaded and then placed in a round pan to rise, then baked.
The dough in this test was too wet and floppy and bubbles escaped preventing the bread from rising properly.
But the texture was more bread like. Getting there.
Experiment 3 – Small sourdough loaf
The next loaf was made with a much drier and firmer dough and left overnight to prove.
A stronger white bread flour, and a drier dough rose better. This loaf had been left overnight to prove.
After baking. Looking good.
Much better results and tasted great
Sourdough bread from wild yeast!