Sourdough Science - Calibrating Your Starter

Here are my experimental results after six hour:

Results After 6 Hours

I've been using sourdough starters for a few years now, but still lack the confidence to rely on them exclusively as the leven for my bread.  The reason for that lack of confidence is that sourdough starters are an unknown quantity.  Their performance varies greatly depending on how old they are, how warm it is in your kitchen and which grain you are using. Strict adherence to a recipe is quite likely to end in disappointment because of all these variables. They also take a lot more time to produce a rise than commercial yeast.  That's not a problem if you can devote all your waking hours to breadmaking but if you work 9 to 5 and like breadmaking too then scheduling your sourdough production is going to be a problem. You run the risk of wasting good ingredients and your investment in time if you lose track of your timing. Given the above I have tended to fall back on dried yeast. (One of my favourites is a 50/50 Rye Sour/Yeasted Wheat  loaf.  The rye sour can develop over a day while the rest of the ingredients, including commercial yeast can be added in the evening to produce a loaf before bedtime.)

But now I'm ready to take the next step: to get to know my sourdough starter by discovering its profile in my current kitchen conditions.

Equipment:

• One jam jar per starter 
• Marker pen
• Watch or clock 
• muslin or paper towel
• Sourdough starter

Method:

• Fill a jam jar to 1/3 it's capacity with newly refreshed starter, carefully avoiding the walls.
• Mark height on the outside of the jar with the marker pen
• Cover jar with a muslin or paper towel
• Wait two hours
• Mark height on the outside of the jar with the marker pen
• Wait two hours
• Mark height on the outside of the jar with the marker pen
• Repeat until the sourghdough starter has fallen back from its highest point.

Results

• My results are all captured in the picture above taken six hours after the experiment began. 
• On the left is a white wheat starter on the right a wholegrain rye starter
• The lowest line marks the starting point, each subsequent line a two hour interval
• The wheat starter grew rapidly for 4 hours but by 6 hours it had peaked and fallen back.
• The rye starter was slow to get going hardly rising in two hours but then steadily rose for 4 more hours. An hour later it hadn't risen any more but hadn't fallen back either 

Conclusion:

• My wheat starter (and dough made from it) needs a 4 hour rise, but should not be left beyond 5 hours
• My rye starter needs at least 5 hours to peak but will hold up for 7 hours

Postscript

• These timings only apply to my starters, although similar conditions should produce similar times.
• Timings will accelerate in the summer. These results were obtained in an unheated Edinburgh kitchen in March

After 4 hours

Top View: Collapsed Wheat Starter

Top View: Rye Starter After 7 Hours