Hi folks,

  After a discussion about batter pH and how to measure it in hieperdepiep’s “how to add cognac to sour cream butter cake-batter” thread, I spoke with some friends of mine and two food scientists here at the local university about the best way to approach this issue. The consensus was that measuring the cake batter’s pH with a probe could be done, but it would not be an accurate measurement due to the way a pH probe measures the pH of a solution and that the oils, emulsions, and proteins in the batter would perturb the measurements. In a paper titled “Effects of sugars in batter formula and baking conditions on 5-hydroxymethylfurfural and furfural formation in sponge cake models.” published in Food Science International by Zhang, Yu-Yu, et al. 2012, a method describing how they measured the pH was described:

A ground sample (0.4 g) of cake was mixed with 20 mL of water and vortexed for 3 min. The mixture was held at ambient temperature for 1 h to separate solid and liquid phases. The pH of the supernatant was measured using a Thermo Orion 868 pH meter (Thermo Fisher Scientific, Inc., Pittsburgh, PA).

  However, I did find another paper by Kilkus, S. where he measured the batter’s pH directly using a pH probe. Although Kilkus was able to measure the batter directly using a probe, it does make me wonder how accurate his measurements were because of the reasons mentioned above. After reading this paper I think this was a student’s paper for a class, but it was still an interesting read. Another issue with this paper was that the author did not specify which model of pH probe he used in his experiments.

Charles, with all of this being said, you might consider using the approach used by Zhang, Yu-Yu, et al. If you decide to purchase the pH probe you mentioned I would be interested to know how your tests go and which method you use.

- MP

Monsieur Pâtisserie - 18 February 2013 05:26 PM

it does make me wonder how accurate his measurements were because of the reasons mentioned above.

Yes, that highlights a point that I make to non-technical folks all the time:  until you know how an instrument works,  you don’t know what it does. Very often an instrument measures a surrogate, rather than the actual phenomenon we’re interested in. The user has to know when the surrogate no longer fairly represents the interesting phenomenon. A pH meter measures electric potential, not acidity itself, and no doubt there is a variety of chemical behavior that can generate some inaccurate results.

Without any way to verify the accuracy of the meter for batters, it doesn’t make any sense for me to have one. It may be that litmus paper is about the best we can do, because it comes a lot closer to measuring the underlying phenomenon, rather than a surrogate. Its resolution is poor, but getting to the nearest whole pH number is probably good enough for our purposes.

(Why don’t we have Tricorders yet??!!)

Whow, you did some good science homework!

I was thinking; would it matter when you didn’t measure the batter, but only the sour ingedient?
Assuming the rest of the ingredients being neutral (unless you have some non-alkalized cocoa). Then you only have to measure the buttermilk or sour cream or lemon (/fruit) juice. Would that make it less complicated?

After we have the PH we need some kind of formula.. think think..
(Ph) x (the amount that is used in the batter) = is countered by (x gram of baking soda).

hieperdepiep - 21 February 2013 05:37 PM

Whow, you did some good science homework!

Thanks, hieperdepiep. After the discussion you started in your thread it got me thinking about this stuff and I really wanted to be able to address this with the best information possible.

hieperdepiep - 21 February 2013 05:37 PM

I was thinking; would it matter when you didn’t measure the batter, but only the sour ingedient?
Assuming the rest of the ingredients being neutral (unless you have some non-alkalized cocoa). Then you only have to measure the buttermilk or sour cream or lemon (/fruit) juice. Would that make it less complicated?

Things still remain a bit complicated with this approach. Measuring the pH of buttermilk or some type of fruit juice might actually be somewhat feasible, but measuring the pH of sour cream directly would likely still pose a problem. As Charles pointed out, the way a pH meter works is it measures a surrogate (electric potential) that can tell us indirectly what the pH is. The definition of pH is that it is the negative logarithm of the hydrogen ion (H+) concentration in solution and therein lies the problem with measuring the pH of sour cream. Sour cream contains water just like cake batter does, but neither are what we consider a water-based solution. And because of all of the other components in them an accurate measurement of the surrogate cannot be made. That’s not to say that cake batter, or sour milk products do not contain acids or have acidity to them, but just that measuring the pH of these substances is not something that can be done accurately. If we assume that all other ingredients are neutral and we have a good idea of what the pH of the acidic components are, then you would be fairly close to knowing what the pH of the cake batter is. However, the reality is that not all of the other ingredients are neutral in their acidity. Recall from what you read in TCB that cake flour is chlorinated (here in the U.S., if you get yours from the UK it is not) from the bleaching process and that makes it more acidic, so that will affect the batter’s pH. And as you pointed out, if it contains alkalized cocoa powder that will affect the overall acidity of the batter, too. There are so many factors that will affect the acidity, so I’m afraid it will remain somewhat complicated to predict the pH based on ingredients, as well as measure the pH with conventional methods we have at our disposal. We can probably make a relatively close guess, but I’m not sure we can get the most accurate measurement of pH for cake batter.

hieperdepiep - 21 February 2013 05:37 PM

After we have the PH we need some kind of formula.. think think..
(Ph) x (the amount that is used in the batter) = is countered by (x gram of baking soda).

What are you trying to determine a formula for here? Are you trying to determine the pH of the batter mixture, how much of the acid from the acidic ingredients has been neutralized, or something different? Sorry for the confusion. You’ve asked some great questions here and I’d really like to help you figure this out, but I just need a little clarification about what you’re trying to determine and we can continue this discussion if you still want to.

- MP

PS - I think you do an excellent job communicating with us in a second language!