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

Abstract

Summary In this study, we compare the histological localisation of phenols and β‐glucan in six cereal cross sections. The concentrations of β‐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. β‐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.

Novel insights into pericarp, protein body globoids of aleurone layer, starchy granules of three cereals gained using atomic force microscopy and environmental scanning electronic microscopy

“…Food microscopy analysis plays an important role in food science, 1 , 2 not only for the morphology of microstructures, but also for providing nutrient localization 3 and their bioaccessibility. 4 Optical microscopy, the oldest and most widely used method, is suitable to detect the structural organization of nutrients in sections of raw and processed foods, such as: cereal caryopses, 5-7 flour and bran, 8 pasta or bread.…”

“… 9 For example, using optical microscopy with the aid of specific staining, it is possible to describe the histological localization of proteins, starch, polyphenols and β-glucan in the cross sections of several cereals. 3 …”

Comparison of industrial and homemade bulgur produced from einkorn wheat (Triticum monococcum ) and durum wheat (Triticum durum ): Physicochemical, nutritional and microtextural properties

“…Wheat starch granules generally exhibit a bimodal distribution in the structure and can be classified as A‐type: 20–35 µm (large) and B‐type: 2–10 µm (small) (Delcour & Hoseney, ). Moreover, in another study, this classification was given as A‐type: with a discoid shape with 15–40 µm diameter, and B‐type: with a round shape with 5–10 µm diameter (Panato, Antonini, Bortolotti, & Ninfali, ). In Figure , the B‐type of granules were captured in SEM images of both wheat sample.…”

In vitro bioaccessibility of avenanthramides in cookies made with malted oat flours

“…Among cereals, oats have attracted nutrition professionals and commercial attention (Pridal et al ., ). The beneficial effects of oats can be traced in part to β‐glucan (Daou & Zhang, ), the active compound in soluble fibre, mainly present in the caryopsis endosperm (Panato et al ., ). Moreover, polyphenols, the active antioxidant ingredients of the aleurone layer of oats (Antonini et al ., ; Panato et al ., ), confer additional health benefits (Peterson, ).…”

“…The beneficial effects of oats can be traced in part to β‐glucan (Daou & Zhang, ), the active compound in soluble fibre, mainly present in the caryopsis endosperm (Panato et al ., ). Moreover, polyphenols, the active antioxidant ingredients of the aleurone layer of oats (Antonini et al ., ; Panato et al ., ), confer additional health benefits (Peterson, ). Avenanthramides (AVNs) are a group of several amino phenolic molecules specifically found in oats (Collins, ).…”