Timing the sourdough sponge

I usually make a sourdough sponge, from some inactive sourdough starter that I take out of the fridge, and a batter of equal amounts of flour and water. Most of the time my sponge develops overnight or while at work. Uptil now, the lifecycle of the sponge has been quite a mystery to me. The amount of leaven I put in has also been very "random", and I suspected that this really has an impact on the sponge.

In some areas timing is of less importance when working with sourdough, since everything is going at a slower pace. However; my experience when it comes to timing of the sponge, is that it's very critical. I've had some ruined atempts trying to bake with an inactive one, and I promise you that it's a recipe for disaster ( http://www.glennbech.com/2006/04/sourdough-disaster.html )

So, I did a little experiment, to see how the amount of "inactive" sourdough starter affects the speed of development. I also wanted to document the total lifecycle, from inactive to inactive.

This is how I set it up

• I took two measuring cups, labeled one "A", and mixed in 18g inactive sourdough starter with 100g flour and 100g water at 23c.

• I took the other measuring cup, labeled it "B" and mixed in 36g inactive sourdough starter with 100g flour and 100g water at 23c. I put a thermometer in one of them and setup up my "proofing lamp" so that the temperature is constant 28-29 degrees C.

• I then checked the experiment every 30 minutes or so, photographed it, and measured volume for each cup.

#	time	Delta	tot. Time	A	B
1	19:44	00:00	00:00	2.9	3
2	20:15	00:31	00:31	2.9	3.1
3	20:48	00:33	01:04	2.95	3.4
4	21:32	00:44	01:48	3.1	4
5	22:03	00:31	02:19	3.5	4.5
6	22:35	00:32	02:51	4	5.2
7	23:09	00:34	03:25	4.8	6
8	23:40	00:31	03:56	5.3	5.5
9	00:12	00:32	04:28	6	5
10	00:39	00:27	04:55	5.8	5.5
11	06:39	06:00	10:55	7	5
12	15:52	09:13	20:08	3	3

For a grahical presentation of the data, click here

To see the picture taken at a certain time, click the entry in the "time" column.

Thoughts and Analysis

• An interesting observation is that both samples, grew exponentialy, decreased in size before "puffing up" one last time with a lot of foam. You can clearly see this in the graph at sample 11 for "A", and 10 for "B.
  
  
• The 18g sponge peaked at 7 hours, the 36g one peaked at 9. This is usefull information if I know I'll be working late or doing something after work.
  
  
• It would be very interesting to know the best time to use the sponge. My best guess would be one the the "peeks" in activity. Since this is the time where you have the largest number of active yeast cells, and lb. Sf. Bacteria.
  
  
• It would be very interesting to know if my data is valid only for my current starter, or if other starters work the same way.
  

Please feel free to comment on this entry or discuss it in the eGullet baking & cooking forum .
You can also email me any comment at mail@glennbech.com