September 23, 2023 - 6:10am
Sourdough Starter and Maillard Reaction in Enriched Doughs
An interesting article on browning with sourdough over at Breadtopia.
https://breadtopia.com/sourdough-starter-and-maillard-reaction-in-enriched-doughs/
I have noticed that the browning of my toast correlates strongly with the pH of the bread. Lower pH equals less browning for identical ingredients.
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I thought yeast were lactose intolerant, they can't consume the milk sugars, so if there is milk in the bread there should be a malliard reaction. Unless there's something else going on in sourdough.
I have noticed too, the lower the pH the less it browns when toasted.
The lower pH from the sourdough results in fewer amino acids available to participate in the Maillard reaction. More amine groups of the amino acids are protonated at lower pH. The protonated amines will not react with aldehydes.or other carbonyls (first step of the Maillard reaction).
As we have the sugar from milk left unconsumed by the yeast. It's the acid affect on the proteins that prevent the malliard effect. In simple terms.
Thank you.
Interesting article. I have also noticed that effect on toast.
I have one quibble with her comparison of acetic acid and lactic acid. The more accurate statement is "acetic acid is weaker per mole than lactic acid." Because acetic acid (MW = 60.05) is an 8× weaker acid than lactic acid (MW = 90.01), the 1.5× difference in MW is not as noticeable.
I hate to seem down on somebody who is clearly interested in the why of what she is doing, so I have to give her credit for curiosity. And if she keeps at it for another few years she can get to where she understands how to do the analysis. There are in this case some missing information: no pH or TTA measurement in any of the samples; no distinction between maillard and caramelization browning; no assessment of what kinds of sugars were in each dough or how much of each. Did the flour have malted barley added or fungal amylase? Was there sucrose added equally to all batches? How is the egg accounted for? Fermentation time is not a good proxy for yeast activity in any case.
I'll concede that the Breadtopia post could not withstand the rigor of a peer-reviewed journal. For that, there would need to be more data, as you stated. Her conclusions were that the sweet stiff levain (SSL) was less acidic. The pH/TTA were not reported, but from what I read here on TFL and elsewhere, that's a pretty safe conclusion. The SSL produced the desired browning. Was it all from the Maillard reaction? Probably, but caramelization may have also contributed. The analysis of types of sugars are likely beyond the instrumentation available.
Successful processes can be developed in the absence of a lot of data. Nearly 30 years of process chemistry in industry inform my conclusion.
If the goal is to develop a billion dollar pharmaceutical, then yes, large amounts of data are collected at every stage of the process. OTOH, if the goal is a product with sales in the thousands instead of millions, then the type of study the author performed would be adequate (time = money). It was a comparative experiment using the same raw materials with levain composition and fermentation time as the variables.
This reminds me of countless processes that my colleagues and I developed. We would use the same RMs and vary a few parameters to get a better yield and/or purity. If the process was reproducible, then it was a successful process. Often the only analysis was final purity assessment. Some processes even did not lend themselves to easy data collection while underway.
If the Sourdough Challah recipe with the sweet stiff levain reproducibly yields a nicely browned loaf, then for the needs of most home bakers, mission accomplished.
For challa I found that oven temperature (and oven timing) and the egg wash that you brush on before going to the oven does a lot to set the color . When the egg wash with a little evaporated milk in it begins to brown it really goes fast so you can wait as long as you dare to get a darker color. There you have the protein and the pentose sugar right on the surface.