With the invention of mechanized steel roller mills and automated sifting devices in the latter part of the 19th century (35), the nutritional characteristics of milled grain changed significantly because the germ and bran were removed in the milling process, leaving flour comprised mainly of endosperm of uniformly small particulate size (35,36). (academic.oup.com)
The Brazilian scientists skinned the kernels of their hulls and puffed up the starchy endosperm in a pressure chamber — the same way Kellogg's makes Corn Pops. (discovermagazine.com)
The benefit was not found with refined grain containing only endosperm. (academic.oup.com)