A young natural leaven, or Sourdough Starter
This is the method which I have used for many years. It has worked every time. Only once has it been a little slow and that was in the Winter when once I didn’t trouble to keep it warm at night.
Everywhere there are long and often complicated procedures telling us how to build a new natural leaven (Sourdough Starter to some). They often involve discarding some of it at intervals, along with careful incremental feeding. The impression given is that they are difficult, fragile even and that they need a lot of care and then you will be successful.
Usually, they will tell you, it will be a week, or even two, before your leaven will be ready.
After many years of using natural leavens I take the opposite view. Once yeast get’s a toe hold it is like a pandemic. It is very hard to stop it.
This method follows the starter's development, not the clock. By using it you will do what your starter needs at the time it needs it and not what an instruction manual guesses you should be doing at that point.
Why discards?
Acidity - One principle behind discarding some of the leaven is based on the need to lower the acidity level. Too much acidity depresses the yeast multiplication and activity. Every time some of the starter is discarded some of the acids, which we are told have built up in the starter, is discarded with it. Then new flour and water will dilute the remaining acids making the environment more suitable for yeast population growth.
The reality: The acidity builds up from yeast activity. A new starter has low yeast activity at first and thus little acidity. Feeds are enough to dilute the little acid that is there. Smelling and tasting your starter from time to time will quickly tell you if it is acidic. The strong acidic tang is unmistakable. It is much the same as a sharp citrus fruit. If it is, then do a discard and feed it. I have never had to do a discard with this fast starter method and I double check with a pH meter. The acidity has always remained well within the acidity range at which yeast can thrive.
Feeding the yeast.
This story is usually along the lines of ‘the yeast needs more food’ and that means more flour.
The reality: The yeast has plenty of flour to feed on. Yeast only ever uses a very small amount of the flour that is present in the leaven.
When we discard some of the starter we are discarding that proportion of the yeast population too. That is, we are discarding some of the yeast population we have been trying to build up. You do not build a bigger chicken farm by shooting half of your chickens at regular intervals.
The Basics
Bread Yeasts work best between 24C, 75F and 28C, 82F. If you can keep the new starter within this range all of the time, it will establish much more quickly. If the temperature drops below 24C, 75F at night then it will merely slow down, or stop, until the temperature rises again. No harm will come to it. The leaven will merely take longer to establish. Do not let it get above 34C, 93F as the yeast will go into stasis. e.g. Deep sleep. But any Lactic Acid Bacteria present will continue and they make acids. That is, you will get more of what you don't want at this stage, Lactobacillus and not yeast.
Keeping the leaven at a good fermentation temperature is crucial if you want to develop your leaven quickly.
The water
Any potable water is suitable. If you live in an area with hard water this is a slight advantage. Heavily chlorinated water might inhibit the yeast. Leave a jug of it on the side overnight and the chlorine will evaporate off.
Where does the Yeast come from?
Just as wine grapes carry the wine yeast on the grape skin in the vineyard, grains carry wild bread yeasts on the grain in the field. These are what we culture in our starter. Most of the yeasts are on the grain husk and much is discarded with the husk when white flour is extracted. I always start a new leaven with whole grain, or wholemeal, flour. The yeast content is much higher. Calling them wild yeasts tends to overlook the fact that these are the yeasts specialised in fermenting that grain. They are not some random wild yeast population.
What does yeast need to feed well?
Yeast needs maltose which is the sugar produced by the amylase found in the flour. The amylase breaks starch down into simple sugars half of which is maltose. The yeast feeds on this. Sugar, the kind we have on our tables is sucrose. Yeast cannot feed very easily on this. The amylase will break that down too, but it is just as happy breaking starch down and it is the amount of amylase present which is the bottleneck. Wholegrain, wholemeal, flour is much higher in amylase compared to white flour. See ‘Boosters’, below, for more information.
Like all plants and animals sugar is not enough for strong growth. Yeast needs protein, minerals and other micronutrients as well. Again these are at low levels in white flour. Again wholemeal flour is high in all of these.
Boosters
As mentioned above higher amylase levels make more sugars available. Fruit such as sultanas and fresh apples have good amounts of amylase in them. The French add fruit and often their choice is apple. Six or seven diced sultanas, or an 1/8 of an apple, crushed or finely diced, is all we need.
I prefer to use whole rye flour which is very high in amylase. I add it at about 10% of the total flour weight. Because it has starch and a high level of nutrients too, it ticks a lot of boxes. A new starter made only with whole rye grain establishes itself exceptionally quickly.
But, I want a white flour leaven
Starting a leaven from scratch is about building up the yeast population. Once it is established and fermenting strongly just take 50g of the leaven and mix it with 200g of white flour and 200g of water and it will effectively be a white leaven ready to use in four to six hours. That fifty grams of whole grain flour will be undetectable in the bread.
My experience of white leavens is that they are not as strong, or robust, as a whole grain leavens. So my starter is always fed whole grain flour. I just feed it across as described above when I want a white leaven, but the ‘mother’ starter is always whole grain.
Feeding in increments
Microbes increase their population faster if there is a good population density. There is a critical yeast population density which, when reached, leads to accelerated population growth. Below that the process is much slower.
For this reason we need to start with a small amount of flour and water. This gets the yeast population over that critical level more quickly.
The general rule of leavens is the x4 maximum rule. Because of the population density effect a sensible maximum for increasing your leaven size is only to increase the size by four times the original flour weight. This keeps the yeast population density high which ensures fast leaven development.
Keeping your starter warm
Brod and Taylor now produce a Natural Leaven incubator. It’s expensive and that money might better be used getting a dough proofer, or putting together a warming arrangement.
Here is one solution:
A simpler way is to buy any one of a number of warming products used in the Home Wine and Beer brewing market. These include thermostatically controlled warming mats. If you use a heated mat, place an upturned bowl over the starter jar to keep the heat surrounding the leaven.
Another fairly cheap method is to get a thermostatically heated seed tray with a Perspex lid. These are good for fermenting dough as well and they keep the dough surface moist.
Bringing it all together. A starter up and ready to use in 48 hours
Keep the temperature ideally at or just below 28C 82F - The maximum safe yeast activity level. 24C 75F is the lower limit for a quick start.
Use whole grain, wholemeal flour, with rye, or just whole rye flour.
Use sultanas, or apple if you are not using whole rye flour, or a whole grain flour.
The formula
Step 1 50 grams of flour and 50g of water mixed in a jar with a loose fitting lid. Wait until you start to see some bubbles*, as a sign that fermentation has begun, before going on to the next step. This might be about 4-8 hours.
Step 2 Feed the leaven with fifty grams of flour and 50 grams of water. If you are using fruit this is the time to add it. Again, wait for bubbles to develop before the next step. Again, this should be 6-8 hours.
Step 3 Repeat step 2.
Step 4 Repeat step 2
Step 5 Repeat step 2.
Step 5 Repeat step 2
*Bubbles. See the picture at the top. I wait for a little more development than this.
At the end of 48 hours I usually have 250g of active leaven and use that for my first bake. Two hundred grams of natural leaven is just right to mix with 400g of flour to make a loaf with a total of 500g of flour. Remember, 100g of that flour is in the leaven. The remaining 50g goes into the fridge waiting to be fed prior to my next bake.
Lactic Acid Bacteria typically take some four weeks to become established in a leaven. They enter the leaven mainly from your hands and your kitchen environment. Please, do not try to speed this process up by adding live yoghurt. Yoghurt LABs are specialists in Casein Chemistry. The LABs that move in naturally are those suited to a dough environment and they use a different chemistry.
Tips: Freshly milled flour is both higher in enzymes and usually it is higher in natural yeasts as well.
White flour from horizontal stone mills such as those used in home milling and water and windmills have the germ rubbed into the white flour. They have higher nutrient levels than roller milled flour.
Off flavours
If your leaven develops off flavours, typically a smell of acetone, think nail polish, then you have unwanted microbes at work. Yeast produces alcohol which suppresses these. If the yeast is too slow to get going then these unwanted microbes can get a foothold. If this happens I discard the starter and start again. Even though these microbes will get pushed out by the yeast later on, the smelly byproducts are still in the starter and I don’t want to eat those.
Any crusts which form on the starter in the future can simply be removed. These are not harmful.
So too any brown liquid that collects on the top of an older starter can be discarded, it is a mix of alcohol, acids and water. Again, these are not harmful.
Whisking the starter
This is a dreamt up fashion doing the rounds on YouTube. It does not help much. There is more about it here:
Finally
There is a fuller article on Natural Leavens here
Tip: Keep the temperature at 26C - 28C 79F - 82F. A common reason for starters not establishing is that they are being kept at low a temperature where the yeast is much less active. 24C 75F is the minimum temperature if you want decent yeast activity. Though you might not have a starter within 48 hours, it is good enough.
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