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    Effect of steam explosion on enzymatic hydrolysis and baking quality of wheat bran
    (Academic Press, 2017) Aktaş Akyıldız, Eda; Mattila, Outi; Sözer, Nesli; Poutanen, Kaisa; Köksel, Hamit; Nordlund, Emilia
    In this study, the effect of steam explosion (SE) treatment on microstructure, enzymatic hydrolysis and baking quality of wheat bran was investigated. Coarse and fine bran were treated at different steam temperatures (120–160 °C) and residence times (5 or 10 min) and then hydrolysed with carbohydrase enzymes. The SE treatment increased water extractable arabinoxylan (WEAX) content from 0.75 to 2.06% and reducing sugars from 0.92 to 2.41% for fine bran. The effect was more pronounced with increased SE temperature and residence time. The highest carbohydrate solubilisation was observed in fine bran at SE treatment of 160 °C, 5 min. WEAX content increased to 3.13% when this bran was incubated without enzyme, while WEAX content increased to 9.14% with enzyme addition. Microscopic analysis indicated that cell wall structure of wheat bran was disrupted by severe SE conditions. Supplementation of SE treated (150 °C, 10 min) bran at 20% replacement level decreased the baking quality of bread. However SE followed by enzymatic hydrolysis increased specific volume and decreased crumb hardness (on the day of baking and after three days of storage). Phytic acid content of bread supplemented with SE treated bran was lower than the one supplemented with untreated bran. © 2017 Elsevier Ltd
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    Extraction of soluble ?-glucan from oat and barley fractions: Process efficiency and dispersion stability
    (Academic Press, 2018) Aktaş Akyıldız, Eda; Sibakov, Juhani K.; Nappa, Marja; Hytönen, Eemeli; Köksel, Hamit; Poutanen, Kaisa
    This study comprises laboratory-scale extraction of soluble ?-glucan (BG) from oat (16 and 32% BG) and barley (12 and 32% BG) fractions, investigation of chemical composition and stability of dispersions prepared from water extracts and techno-economic evaluation for small industrial scale production. Oat and barley fractions were hydrolysed with an enzyme preparation and BG was extracted from hydrolysed samples by boiling water. Enzymatic hydrolysis resulted in medium molecular weight (MW = 38,500–69,400 g/mol) after 2 h incubation with 10 nkat ?-glucanase activity/g bran and low MW (11,800–22,600 g/mol) after 4 h incubation with 50 nkat/g bran. MW and concentration of BG affected the stability of dispersions during storage. Barley fractions, after both 2 and 4 h hydrolysis, resulted in higher viscosities than oat fractions. MW of BG in soluble barley fractions was only slightly higher, but the difference in MW does not seem to be adequate to justify the observed viscosity differences. Barley extracts contained higher amounts of starch, however, starch did not have a distinct effect on viscosity. Techno-economic analysis for production process with feedstock design capacity of 100 kg/h showed that production costs varied from 0.06 to 0.11€/g soluble BG. Raw material and capital charge were key cost factors. © 2018 Elsevier Ltd