Flour
41. Whether or not dry flour is considered chometz depends on if water was added during the grinding process. This could be different for any given place or time.
42. “Wet flour.” Strictly speaking, flour made from wet wheat may be used for matzah on Pesach, since it does not display signs of becoming chometz. However, the Ge’onim forbade its use for matzah (שו"ע סי' תנ"ג ס"ה ). Even those who do not sell true chometz to a non-Jew may certainly rely on its sale (תשובות והנהגות ח"א סי' ש"ט ).
43. Regular flour. For the most part, wheat kernels today are not soaked before being ground. However, many times the kernels are sprayed with a bit of water to ease the removal of the shell during the grinding. Even then, signs of becoming chometz are not visible on the wheat, even after several hours. Therefore, the poskim rule that regular flour is not chometz (תשובות והנהגות שם ).
44. Thus, even the machmirim rely on its sale to a non-Jew (חזו"א, הגרי"י קנייבסקי, ארחות רבינו ח"ב אות י"ט, הגריש"א, אשרי האיש ח"ג פס"ב אות ז'). Being machmir on this is an excessive chumra for a potential issur derabanan.
45. Dry flour. However, after Pesach some only use “dry flour” [the wheat was not sprayed at all with water] even if it was ground before Pesach. This flour is no different than flour ground after Pesach. [Many products produced after Pesach have a label indicating they were made from flour ground after Pesach or dry flour ground before Pesach (מדריך הכשרות עדה''ח תשפ''ב ).]
Whole Wheat
46. Whole wheat products, even if the flour has no concern of chometz, often contain raw materials from before Pesach, e.g., gluten or malt [which are chometz], added. Therefore, even if they are ground and baked after Pesach, it must be verified that the raw materials added were purchased from a non-Jew after Pesach.
For Small Children
47. Based on the above, there is no reason to be machmir to only feed children flour that was ground after Pesach, as there is plenty to rely on to use even regular flour ground before Pesach. One should not make his children hungry or weak, especially when they are learning, because of chumras over an issur derabanan.
