Electron microscopy and composition of raw acorn starch in relation to in vivo starch digestibility

Abstract

The structure and composition of starch play an important role as co-factors affecting raw starch digestibility: such features were investigated in raw acorn starch from the most diffused oak trees in the Mediterranean basin. A total of 620 whole ripe acorns from Holm (Quercus ilex L., n = 198), Downy (Quercus pubescens Willd., n = 207) and Cork (Quercus suber L., n = 215) oaks sampled on the Sardinia Isle (40° 56' 0'' N; 9° 4' 0'' E; 545 m above the mean sea level) in the same geographical area, were analyzed for their chemical composition. The starch contents ranged between 51.2% and 53.5% of dry matter. The starch granules displayed a spheroid/ovoid and cylindrical shape; on scanning electron microscopic (SEM) analyses, a bimodal distribution of starch granule size was observed both for Holm and Cork oak acorns, whereas the starch granules of Downy oak acorns showed diameters between 10.2 and 13.8 μm. The specific amylose to amylopectin ratio of acorn starch was 25.8%, 19.5% and 34.0% in the Holm, Downy and Cork oaks, respectively. The (13)C Nuclear Magnetic Resonance (NMR) signal analysis displayed a pivotal spectrum for the identification of the amylose peaks in raw acorn starch, as a basis for the amylose to amylopectin ratio determination.

Physicochemical and Morphological Properties of a Small Granule Legume Starch With Atypical Properties From Wild Mango (Cordyla africana L.) Seeds: A Comparison to Maize, Pea, and Kidney Bean Starch

“…The amylose content of wild mango starch (25.5 ± 0.2% w/w dwb of starch) was not significantly different from that of maize starch (24.4 ± 1.0% w/w dwb), but was significantly ( p ≤ 0.05) lower than that of bean (30.9 ± 1.3% w/w dwb) and pea (31.7 ± 0.5% w/w dwb) starches. The amylose content of the wild mango seed starch was within the range (19.5–34.0%) reported for acorn starch . The amylose contents of bean, pea, and maize starches reported in the present study were consistent with those reported in the literature for maize, pea, and bean starches .…”

“…The wild mango starch granules were also smaller than similarly shaped granules reported in literature, such as cassava (15 µm), jackfruit (7.6 µm), tannia (14.7 µm), and sago (30 µm) starch granules. The wild mango seed starch granules were also smaller than those reported for acorn starch (10.2–43.3 μm) . The wild mango starch granule size showed a normal/unimodal distribution with a narrower distribution than bean, pea, and maize starches (Figure ).…”

Impact of Acorn Flour on Gluten-Free Dough Rheology Properties

“…Paste retrogradation is influenced by the amylose content and also by the structural arrangement of the starch chains [37,38]. According to Hager et al [35], buckwheat starch presents a granular shape, whereas acorn starch granules show a spheroid/ovoid and cylindrical shape [43].…”

“…Since our study is focused on acorn flour, it is important to highlight that among the different species of oak trees, the acorn starch is also different due to taxonomic characteristics of the plant [43]. For this reason, to make possible the comparison about starch behaviour, we used the studies based on the same species: Quercus rotundifolia and Quercus ilex from Cappai et al [43] and Correia et al [39].…”

Response of Fattening Rabbits with Acorns (Quercus pubescens Willd.) Combined in the Diet: First Acquaintances on Growth Performance, Carcass Traits and Perirenal Fatty Acid Profile

“…Nutrient composition of acorns identifies these fruits as energy-rich feedstuffs (starch 512–571 g and 42–63 g crude fat content in kg dry matter) [ 14 ]. Therefore, acorns can serve as concentrate feeds in extensive breeding systems [ 14 ] chiefly in feed mixtures [ 15 , 16 ] due to biologically active compounds (polyphenols profile) and to the peculiar pattern of fatty acids [ 14 ]. A number of studies on the use of acorns was carried out in pigs and, to a lesser extent, in ruminants and poultry.…”