The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Sour losing its sour

Doughboy44's picture
Doughboy44

Sour losing its sour

Hi Guys

Recently noticed our sourdough no being as sour as usual. Can we do something with our levain to increase the sour flavour. We currently feed it every 24hrs with 100% flour 50% water and 50% old levain. Mix this until incorporated and then place in container for the next days sour if we make. 

Some advice would be great.

joyfulbaker's picture
joyfulbaker

You might feed it every 12 hours for a couple of days to give it a boost.  I use a 1-2-3 ratio (1 part sour, 2 parts water, 3 parts fresh flour) that works nicely.  There must be other factors at play if your usual results aren't the same with the same procedure and amounts; maybe the weather, the humidity, the age of the flour, something different about the water, etc.  I find that my starter increases the "sour" flavor if, after boosting it for a couple of days, I let it sit for 2 or even 3 days in the fridge.  Good luck!

Doc.Dough's picture
Doc.Dough

I don't know what temperature you are experiencing, but a 1:1:2 refresh at 24 hr intervals is insufficient to dilute the acid sufficiently to allow the LAB to replicate. Try refreshing with 1:10:20 at 12 hr intervals until it again has a sour flavor (it should only take two or three cycles).  The LAB growth rate is a fairly strong function of pH.  When the post-refresh pH is regularly below ~4.3 the LAB growth rate drops below that of the yeast and the LAB population declines with each refresh cycle.  To recover, you must assure that the post-refresh pH is  above ~5 and this requires a higher dilution ratio.  Because the growth rate of the LAB is higher than that of the yeast at all temperatures (assuming that the pH > 4.3)  it stops replicating when the pH drops to ~3.8.  After that the LAB produces acid but does not replicate.  Enough cycles at low pH will deplete the starter of LAB to the point where it is no longer sour.

nicodvb's picture
nicodvb

Doc Dough, what's the correct way to use a ph-meter? So far I've been sticking it directly in the starter/preferment but recently I found a site advising to dissolve 15 gr of starter in 100 gr of deionized water. I always used the same method without considering the different hydratations of the preferments and I always wondered if I was doing the right thing or something completely wrong.

Can you explain, please?

Doc.Dough's picture
Doc.Dough

I don't know what kind of pH meter you have, but the test solution needs to be fluid enough to fully contact the sensor.  If you are using a glass probe it is pretty easy, but with an ISFET the sensor is generally recessed and a stiff starter may not fully contact the small area that is active.  In that case you can dilute the sample with some DI water.  For the accuracy you need it won't affect the outcome of the measurement significantly (in fact you can use RO filtered water at 7 ppm total dissolved solids and be just fine).  For checking post-refresh pH, even paper strips will work as an adequate indicator.

Doc.Dough's picture
Doc.Dough

In sourdough starter, and in sourdough bread, the acids that dominate are all weak acids (lactic, acetic, and perhaps carbonic at some points) and the pH does not change significantly when you dilute the solution with DI water.  The amount that is ionized is pretty much independent of the acid concentration, so you can have a high concentration of a weak acid or a low concentration of the same weak acid and the pH will be about the same.  You can read about Kc, Ka and pKa in a chemistry text if you are interested in more detail.

This is why pH is not a good indicator of how sour a bread will taste since you taste total titratable acid (TTA) and not pH. TTA measures acid concentration, not hydrogen ion concentration (pH).

joyfulbaker's picture
joyfulbaker

For those of us who don't have a background in chemistry (I studied English lang. and lit. and philosophy), what would be your recommendation for measurements for flour (assuming a "white" starter), water and "old" starter--in grams or (yes! even) ounces.  The 1:10:20 ratio is a little puzzling (1 oz starter, 10 oz water, 10 oz flour??).  I don't have a pH meter, nor do I intend to get one.  So far I've been baking great bread with the 1:2:3 ratio on a 12-hour schedule, refreshed for 2 days after refrigeration for up to a week.  

Thanks,

Joyful

Doc.Dough's picture
Doc.Dough

I use a refresh ratio of somewhere around 1:7:7 because it works for me. 

I believe the convention on this board is to use the notation (old starter:water:flour), so 1:10:10 is one part by weight starter, 10 parts by weight water, and 10 parts by weight flour.  I use grams, but you can use grains, or pennyweight, or metric tons.  There are many people who use 1:1:1 or 1:2:2, and if it works for them that is just great, but after many readings of Ganzle's paper (Modeling of Growth of Lactobacillus sanfranciscensis and Candida milleri in Response to Process Parameters of Sourdough Fermentation - availabel at: http://aem.asm.org/content/64/7/2616.full) and a lot of local experimentation and modeling I have settled on using Ganzle's model without modification. 

One result is that I use a refresh ratio that respects both the temperature in my kitchen and the constraints on my time, and it changes over the seasons and with circumstances.  The only requirement is that I plan half a day in advance.  The time to maturity for a 1:10:10 refresh is 8 to 16 hrs, and the difference between a 1:10:10 and a 1:20:20 is one doubling time (about 3 hrs at 23°C).  If for some reason I will not be able to do at least one daily refresh (usually due to travel) I will refrigerate my starter one hour after refreshing it at 1:10:10.  My refrigerator maintains 36°F where I store the starter so I can let it coast for a week, after which the LAB have grown by a factor of 10 while the yeast have only grown by a factor of 2.  Thus it is important to bring it back to room temperature for a couple of hours (this does not hurt the LAB) and then refresh it at least once at 1:10:10 to rebalance the numerical ratio of LAB to yeast (about 100:1 in a healthy starter).  This refreshment takes only 12-16 hrs overnight and I am back in business. 

I also maintain only small quantities of starter (30 g) since I can generate as much as I need in half a day - a (1:20:20) refresh starting with my 30 g yields 1200g of starter in 8-16 hours (in part because I can precisely control the temperature I want it to run at) and that will make a lot of bread.

Hope this helps.

 

Doughboy44's picture
Doughboy44

Thanks you guys for all the info I will start on some of the ideas and see which works for me.

joyfulbaker's picture
joyfulbaker

for taking the time to explain further.  While some of it is still over my head, I do understand that you are placing the old starter in a much more highly diluted mixture than I have been.  I also see that you are using refrigeration in a way so as to make the fermentation schedule flexible.  There should be a course in "Bread Chemistry for Dummies"--maybe you'll give one online.  If it's within my budget, I'll take it!  I'm so used to using ounces (not such a good thing); I'm going to move to grams so I can get a feeling for how much quantity in how many grams (I have that sense for ounces at present).  Your refrigerator is much colder than mine (I keep it at 40 dF, sometimes 39), and I'm not sure what the advantage is.  Since I'm getting busier (baking for a caterer these days), I appreciate ways to save time, as it's sometimes tedious to do the refreshing every 4 or 5 days (again, the 1:2:3 ratio) for two starters (I regularly bake Hamelman's mixed starter levain with the rye and "white" starters--a delicious everyday bread).

That did help--a bit. 

Joyful

PS:  I am enjoying the new Bosch.  When I have some time, I am going to post some pictures of the bagel process; I mixed the dough (ITJB formula now upped to 55% hydration) on the Bosch; it went beautifully and much easier to roll and seal!

Doc.Dough's picture
Doc.Dough

With a 1:2:3 refresh and a 40°F storage temperature, the LAB will shut down (for low pH) after about 3 days, while the yeast will not finish their meal until day 8 so you are still relatively OK.  There will be enough LAB to restart the process when you get around to feeding it.  What I don't know is how fast the LAB die off after their replication is inhibited by low pH.  There is ample evidence that you can still recover a starter that has been left in the refrigerator for 6 weeks or more though it is not clear that the dominant LAB species in the recovered starter is the same as what it was put into the cooler.

I am glad that you found a hydration level for your bagels that works for both you and the mixer.  I make a bread twist that I call a Crustick using approximately the same dough (steamed and baked in the combi instead of being boiled and then baked):

https://picasaweb.google.com/DocDough/Crusticks?authuser=0&authkey=Gv1sRgCMT7ksr19b2lqAE&feat=directlink

 

joyfulbaker's picture
joyfulbaker

I'm amazed at how you can tell all this, but then, I'm without any chemistry knowledge.  But I can digest (oops! NPI!) the outcomes, and I see the qualitative difference in the texture of the starter after about 5-7 days at 40 dF.  It gets "runny" and thins out.  Has an acidic odor (you'll know just why), "sour" I suppose, but the consistency is much more liquid.  So when it's been close to a week in the chiller, I refresh twice (12-hour intervals) and then back in the chiller if I'm not ready to bake with it.

Your Crusticks look intriguing; all those blisters!  The surface crust, in the photo at least, looks very light, unlike the golden brown bagels.  The moisture from the steaming, I suppose.  Wonder about the chew and the crumb.  Very creative!

Doc.Dough's picture
Doc.Dough

Joyful,

The Crustick formula was developed to maximize the ratio of crust to crumb.  It took a year to work through the process to the point where I had it under control and could predict the outcome every time. There is a balance between how dark the bottom is and how dark the top is because I prefer to use a perforated Teflon-coated baking sheet.  If I bake on Silpat to the same end point (crumb@200°F) the top is dark and the bottom is light.  The timing is critical so while it isn't yet perfect it is pretty good - and chewy too. Much like a good bagel; perhaps a bit more chew because it has a smaller diameter.