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Total Titratable Acidity (TTA)

alcophile's picture
alcophile

Total Titratable Acidity (TTA)

A recent discussion of TTA in another thread prompted me to start this thread. This question is aimed at chemistry nerds (like me) and/or diehard sourdough users.

TTA is considered an important parameter in sourdough development. I don't have a copy of the AACC Method 02-31.01, Titratable Acidity, but I understand the titration procedure. What I haven't been able to figure out is the convention for the units used for reporting TTA. A lot of publications will state the acidity in mL of NaOH, but that number is meaningless without knowing the sample size that was used for the analysis. I watched some videos from Puratos on the titration and the scientist shows an equation:

HOW TO MEASURE THE ACIDITY OF YOUR SOURDOUGH

Volume 0.1 M NaOH / Weight of sourdough (≈10 g) * 10 = TTA

Why does he multiply by 10?

Is there a convention for reporting the TTA in sourdough? My guess is that it is milliequivalents (meq or mequiv) acid per 100 g of sourdough. Can anyone confirm this?

Thanks!

Ilya Flyamer's picture
Ilya Flyamer

I think it's to obtain a value corresponding to so called Thorner's degree acidity, which is measure for 100 g sample, not 10 g? And/or it's just a convention to standardize to 100 g of sample.

MikeV's picture
MikeV

I've never done this myself, but looked it up in a couple different books that mention it (T. Teffri-Chambelland's "Traité de Boulangerie au Levain" and L. Geißler's "Brotbackbuch #4"). Both define the units as the volume in mL of 0.1 M NaOH needed to titrate a 10 g dough sample.

In the video you link to, he divides the mL needed for titration by the actual weight in grams of the sample he used. Therefore he needs to multiply again by 10 grams to obtain the mL of base per 10 g.

Interestingly, the German source actually defines a unit for this TTA metric: the °Sr.
(I presume this is derived from "Säuregrad," which is their word for TTA)

Ilya Flyamer's picture
Ilya Flyamer

Ha I guess I either screwed up the arithmetic or missed something in the formula in my answer haha. Indeed it would be for 10 g.

I found a Russian standard with the definition of degree of acidity for dough, which says it's the volume in cm³ of 1M NaOH or KOH to neutralize acids in 100 g of product. So that would be the same as volume of 0.1M base for 10g product.

https://docs.cntd.ru/document/1200021542

Gadjowheaty's picture
Gadjowheaty

Sorry for the hijack seque, Ilya et al, but Mike, those are some serious books!   I'd forgotten about the Boulangerie Coffret.  I see on Amazon they have a 1 and 2 book version.  Mind telling me which you have, and what your opinion on it is?

Secondly, planning to slowly gather up  L. Geißler's books over time.  I have already learned a good deal from his blog (in fact, baked his Weizenmischbrot mit Dinkel and Berliner Roggenmischbrot yesterday).  I'd planned to start with his sauerteig book - any suggestions on a good one to begin with, and impressions of the series overall?

Finally, would really love to find the Brotland Deutschland books.  I can find No. 2, but really, basically, I'm finding the series is not available (especially his first one).  Do you or anyone know where to find these bookss?

MikeV's picture
MikeV

I found "Traité" to be really good, especially the theory book: a very nice overview of the processes going on in sourdough baking, accessibly written and well-illustrated. The "Practice" section is oriented towards an experienced/professional baker, it is not a "learn to bake" book. The links you show both look the same to me - it is a two-book set ("theory" + "practice"). 

Geißler is an extremely prolific author, I have not read/looked at most of his books ... Brotbackbuch #2 is a nice collection of "fundamental" bread recipes (wheat, spelt, rye, various mixes, whole wheat, etc) crossed with different preparation approaches (commercial yeast, sourdough, no-knead, overnight), both very practical and insightful. #4 (Sauerteig) has a lot of in-depth discussion on sourdough biology, if your German level is limited it will be very tough going. If you want to learn to bake some German "standards" I would recommend #2 over it.

Gadjowheaty's picture
Gadjowheaty

Yes, sorry Mike, I did see they're the same.  With one offered for $240 and the other $90, I thought they were different.  My mistake.

Thanks on the German texts.  Good to know about Brotbackbuch #2 because #4, Sauerteig, caught my eye first.  I am really on the hunt for Brotland Deutschland but they seem impossible to find.  What do you think of Schwartz Brot Gold, by Brotz and Swoboda? 

charbono's picture
charbono

In the wine world, TA is expressed as, for example, .75 g/100 ml. However, some go ahead and multiply by 10 to give a cleaner expression: 7.5 g/L.

 

alcophile's picture
alcophile

@Ilya—Math was never my strong subject. That's why I focused on organic chemistry. I confused myself on this calculation.

@MikeV—The titration affords the mmol (or mequiv) of acid per gram of sourdough. So, it makes sense that the value would be multplied by 10 for a 10 g sample. But I really would like to get my hands on the AACC method to see if a 10 g sample is always used for the TTA analysis by convention. The problem I have is that the scientific literature is not consistent in always using that convention for reporting. I have seen several different ways the TTA is reported. I wish units for the TTA would be used instead.

@charbono—I think the 10× correction is also used here for a cleaner expression just like the wine example

MikeV's picture
MikeV

I suppose at the end of the day the unit choice will always be a matter of convention - just because the AACC defines a particular method, doesn't mean a Russian or a French or a Japanese analyst will also follow it! The sources I mentioned above both indicate that it is "standard" to use 10g of sourdough material in the titration (one even specifies + 100 ml of distilled water), but I guess that means "standard" in their local context.

alcophile's picture
alcophile

Mike,

Thanks for the response. My problem is that I'm used to chemistry publications generally using ACS and IUPAC/SI units and conventions for all numerical data, no matter where the research was conducted. One of the few exceptions allowed (thank goodness!) is the continued use of liters for volume instead of the preferred cubic meter.

As I mentioned earlier, the problem I had was that some of the literature articles I looked at would state that the AACC method was used and then show data in "mL NaOH" for the acidity without listing the sample size. Other articles would report TTA using different units or samples sizes. Without having access to the AACC method, it was difficult to know how to compare the data. It also didn't help that the Puratos scientist used "degrees" as the unit in his video. I had no idea what this was until you provided that info.

 

Gadjowheaty's picture
Gadjowheaty

Thanks for the thread alcophile. 

FWIW, just a snippet from a source I can't recall, on customary units from countries:

"As already mentioned, it is vital that you use a solution of known normality. You can either buy this or make it yourself. Making it yourself is not difficult, but if you’re not up for it, you can buy it. The normality available commercially may vary with your location. This is because different parts of the world use different standard methods and units to measure dairy products. You can choose from the following values commonly used with TA, and prepare the normality accordingly:

 

Soxhlet Henkel degrees (°SH). This unit is used in central Europe, except in France and the Netherlands. The commercial standard method is to use 100 ml milk and NaOH with normality of N/4 (.25 N).

Therner degrees (°Th). This unit is used in Sweden and the former USSR countries. The commercial standard method is to use 100 ml milk diluted with 200 ml water and NaOH that has a normality of N/10 (.1 N)

Dornic degrees (°D). This unit is used in the Netherlands and France. The commercial standard method is to use 100 ml milk and NaOH with normality of N/9 (.11 N).

Per cent lactic acid (% l.a.). This unit is used in the “British” countries, that is, USA, UK, Canada, Australia, and New Zealand. It’s really the Dornic degree divided by 100."