pH guided dough processing - a possible breakthrough!
I have posted several times about monitoring pH at various points in the sourdough breadmaking process and how my fermented dough and bread pHs seemed to be higher than those quoted by other bakers.
I thought this must be something to do with my starters (I have tried several different ones), but I hardly ever got crumb pHs below 4.40.
I have now come to a more interesting - and radical - conclusion. It's early days, but I am minded to think that the calcium carbonate present in nearly all UK flour has a neutralising effect on the sourdough acids.
All UK wheat four, other than wholemeal, is, by law, fortified with calcium carbonate (as well as B-vitamins, iron and (soon) folic acid).
The calcium carbonate addition rate was in the range 235-390mg CaCO3 per 100g of flour, but was recently amended to a fixed 300mg per 100g. So if you make a dough with 1000g of flour it will contain 3 grams of CaCO3. My thoughts are that this calcium carbonate (being a weak base) is neutralising the sourdough lactic and acetic acids.
I've done a couple of bakes with imported Italian fliours and achieved crumb pHs of 4.14 (mainly white bread) and 3.98 ( 40% wholemeal).
I know that some countries mandate flour fortification, but not all, so others may not have observed this pH discrepancy.
BTW I've nothing against flour fortification, other than this unfortunate effect on dough pH. Interestingly, the lower pH does seem to (positively) alter the appearance of the bread crumb, to give a slighly translucent, shimmery look.
I look forward to any pH results from other bakers using fortified flours.
Lance
I'm curious; is calcium carbonate listed on the package as an ingredient, along with the amount of it used?
Your comment about the appearance of the bread crumb stuck a chord. I've been doing oven experiments, making CLAS white-bread sourdough loaves as the constant, and using the cheapest flour available (Walmart house brand) so as not to be wasteful (some of it gets tossed immediately). And I'm experiencing the exact thing you described, a less-appealing (good color but less 'sheen') crust and crumb appearance with this flour. So I wonder if the big US mills are using the same stuff. It's not listed on the label...
In the US, flour enrichment legal requirements are given in 21CFR137.165. Calcium enrichment is optional and must be included on the label. However, the flour may also be "acidified" with monocalcium phosphate. If there is not enough of the phosphate to meet the amount of calcium required for calcium enrichment, then the label may not claim there is calcium enrichment.
So far as I can see, there's no requirement to label the presence of monocalcium phosphate if it doesn't provide that level of calcium.
The enriched white flours I usually bake with do not list calcium on the label.
So it *could* be present in small amounts, and be unlisted.
I have bags of Gold Medal and Traders Joes unbleached AP here, and have baked with both in the last month. Neither list calcium, and neither have the "dull sheen".
I do not recall ever seeing calcium carbonate on the labels of any flours that I have purchased in Canada or the US. But your thoughts are very interesting. Using Canadian flours I have regularly achieved pH < 4.0. I’ll have to keep my eyes out for calcium carbonate on the labels of flours I purchase in the future.
Benny
The US requirements for optional calcium enrichment do not specify what form that calcium must be in. But if it's there as an enrichment, it must be included on the nutrition label. So for US flour, if calcium is not on the label it has not been added, unless a small amount has been added in the phosphate form to mildly "acidify" the flour.
A few more countries' fortification policies are listed in Table 1 in this document.
Lance
If you are seeing pH values you think are wrong, your pH meter might be out of calibration. Remember that pH is a log scale measurement which means that each whole unit represents a 10 fold change in acidity. The acids produced by fermentation processes are weak acids, with vinegar (acetic acid) probably the strongest with a pH of 2.5. Ascorbic acid (Vitamin C) which is commonly used as an additive has a pH around 3. pH of sourdough bread can vary depending a number of factors.
Despite my background as a chemist, I never had the inclination to measure the pH of my bread(s). I'm content if it just tastes good.
If you really want to understand how it works you should grab a general chemistry text and read a chapter on weak acids and buffer solutions.
Or maybe I could dig out my old Chemistry degree course notes?
Please expand Mike.
Lance