Through all of the experiments I have conducted on this thread, one of the things that has always intrigued me is the appearance of dark specks and an overall grayish tinge on the tops of dough balls during cold fermentation. Examples of what I am referring to can be seen in the first photo posted at http://www.pizzamaking.com/forum/index.php/topic,3985.msg35370.html#msg35370
(Reply 23) and in the second photo posted at http://www.pizzamaking.com/forum/index.php/topic,3985.msg36081.html#msg36081
Before I started making doughs that went beyond 4 or 5 days, I had never seen doughs with the appearances as shown in the abovereferenced posts. And, although the “gray” dough balls produced some of the best crusts and pizzas I have made, I was still puzzled as to what was causing the gray appearance. I might add that the grayish tinge and specks appeared only on the tops of dough balls. The bottoms were quite normal, even up to 15 days of cold fermentation. Usually the first signs of the dark specks appeared at around 6-7 days of cold fermentation, although in one case, as described at Reply 29 referenced above, the spots and gray coloration of the dough occurred after about 2-3 days.
Initially, I thought that maybe the dark specks were dead yeast, or possibly yeast that was affected in some way at around 6-7 days because of the prolonged presence of oil on the outer surfaces of the dough balls. When I researched the matter, one of the few explanations I could find was that the dark specks were due to oxidation of bran particles in the dough (“old dough”). This explanation came from John Correll at his Encyclopizza
tome, at section 18 at http://www.correllconcepts.com/Encyclopizza/07_Dough_trouble-shooting/07_dough-crust_trouble-shooting.htm#_Toc533730478.
Since I was using high-gluten flour (KASL), this explanation seemed plausible because high-gluten flours are more likely to have more bran than other white flours, even though millers go to great lengths to keep the bran levels low in just about all white flours. Also, high-gluten flours have higher ash values than other white flours, which can be taken as an indication that the flours were milled closer to the outer bran/aleurone layer of the endosperm where the mineral content is higher than at the center. It is the higher mineral content that is reflected in the higher ash values of the incinerated samples of high-gluten flours. As best I can determine, the KASL has an ash value of 0.52 +/- 0.02%. By contrast, for the KA all-purpose flour and bread flour, I believe the corresponding number is 0.48 +/-0.02% (see http://www.kingarthurflour.com/stuff/contentmgr/files/85e624febf29e4c7836066cc68c71648/miscdocs/BFS%20Specs%20-%20Customer%20Copy.pdf
To see whether the dark specks were limited to doughs based on high-gluten flours, I made several test doughs using all-purpose flour and bread flour. I allowed the test doughs to cold ferment for several days, watching daily for the appearance of the dark specks. In just about all cases, I let the dough ferment past their useful lives, just to be sure that enough time was provided for the specks to appear, if they were ever going to do so. I also tested plastic (Rubbermaid) and metal containers, to see if the type of container might have contributed in some way to the occurrence of the specks. In some of the test doughs, I used ADY in lieu of IDY, to see if that mattered, and in others I omitted the oil altogether. This was done to see if the oil was a possible factor, either in or on the dough, particularly for a dough that was allowed to ferment for 6 or more days, where I had little past experience
When the tests were done and I evaluated the results, I concluded that it was only the high-gluten doughs (KASL) that had the dark specks. I saw no evidence of specks in the doughs made from all-purpose flour or bread flour, even after 7 days, and up to 9 days in a few cases. The type of yeast didn’t seem to matter, whether it was used early or late in the dough making process, and the presence or lack of oil didn’t seem to matter. There could well be some other explanation, but for now the best I can offer is that it is only the KASL high-gluten flour that seems to be prone to the formation of the dark specks in doughs that cold ferment for more than 6-7 days. I wish that I could say that the appearance of the specks is a good indicator that the dough should be used shortly thereafter, but the specks can persist and even increase with time. The appearance of bubbles on the upper surface of the dough, along with smaller gas bubbles at the sides and bottom, seems to be a more reliable indicator, whether the specks exist or not. I saw this most clearly with the all-purpose and bread flour doughs. At some point, they all developed the bubbles. But no dark specks.
EDIT (10/2/13): For a substitute link for the Correll Encyclopizza item referenced above, see http://web.archive.org/web/20040602213637/http://correllconcepts.com/Encyclopizza/07_Dough_trouble-shooting/07_dough-crust_trouble-shooting.htm#_Toc533730478