The histology of grain caryopses for nutrient location: a comparative study of six cereals

In this study, we compare the histological localisation of phenols and beta-glucan in six cereal cross sections. The concentrations of beta-glucan and total phenols in whole grain flour (WGF) were also investigated to provide their nutrient content in grams. Cross sections of durum, soft, einkorn and emmer wheat, oats and barley were stained with Azan Trichrome (ATH) and periodic acid-Schiff (PAS) to characterise the morphology and cytohistology of the living cells in the aleurone, subaleurone and germ, as well as the a-nucleated cells in the starchy endosperm. Phenol localisation in the outer layers was performed by fluorescence microscopy due to the presence of ferulic acid. beta-Glucan, examined with Calcofluor White staining, was found to be located primarily in the subaleurone layer and starchy endosperm of oats and barley. Our findings shed light on why WGF nutritional value is markedly reduced when the bran is removed through milling.