Effect of Endogenous Lipids and Proteins on the Antioxidant, in vitro Starch Digestibility, and Pasting Properties of Sorghum Flour

This study evaluated the effect of endogenous lipids and proteins on the antioxidants, starch digestibility, and pasting properties of sorghum (Sorghum bicolor) flour (SF). Endogenous lipids and/or proteins were removed from different portions of SF to obtain defatted (DF), deproteinized (DP), and defatted and deproteinized (DF-DP) flours. Bioactive constituents (total phenolics, tannins, flavonoids, saponins, and anthocyanins), antioxidant activities [2,2-Azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) radical cation (ABTS*+) and 2, 2-Diphenyl-2-picrylhydrazyl radical (DPPH*) scavenging activities, reducing power, and Fe2+ chelating capacity], starch, amylose, starch hydrolysis index (HI), estimated glycemic index (eGI), and pasting properties of treated and control (untreated) flours were determined. The control flour (SF) had significantly higher (p < 0.05) levels of all the bioactive constituents and antioxidant activity tested than the DF, DP, and DF-DP flours, while the DF-DP flour had the least levels of bioactive constituents and antioxidant activity. In contrast, the starch, amylose, HI, and eGI were consistently in the order of DF-DP > DF > DP > control flour (p < 0.05). The control flour had the highest (p < 0.05) peak viscosity, and the least peak time and pasting temperature, while the DF flour had the highest final viscosity. Therefore, endogenous lipids and proteins contribute to the antioxidant, starch digestibility, and pasting properties of sorghum flour.

Effect of Hulless Barley Flours on Dough Rheological Properties, Baking Quality, and Starch Digestibility of Wheat Bread

Hulless barley (Hordeum vulgare L.), also known as highland barley, contains nutritional compounds, such as β-glucan and polyphenol, which can be added to wheat flour to improve the dough nutritional quality. In this study, different formulated dough samples were obtained by individually adding four hulless barley flours into flour of a wheat variety (Jimai 44, designated as JM) which has very strong gluten. The effects of hulless barley supplementation on gluten structure, dough rheological properties, bread-making properties, and starch digestibility were assessed. The results showed that compared with JM dough, substitution of hulless barley flour to wheat flour at levels ranging from 10 to 40% negatively affected gluten micro-structure and dough mixing behavior, because the cross-links of gluten network were partially broken and the dough development time and stability time were shortened. For the hulless barley-supplemented bread, specific volume was significantly (P < 0.05) increased while springiness was not greatly changed. Furthermore, the hydrolysed starch rate in hulless barley-supplemented bread was decreased, compared with that in JM bread. Importantly, the contents of β-glucan, polyphenols and flavonoids in hulless barley-supplemented bread were 132.61–160.87%, 5.71–48.57%, and 25–293.75% higher than those in JM bread, respectively. Taken together, the hulless barley-supplemented bread has been fortified with enhanced nutritional components, more desirable bread-making quality, and improved starch hydrolytic properties, which shows a great potential to use hulless barley as a health supplement.