Browsing by Author "Ubehend Gunter"

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    Batter rheology and bread texture of sorghum‐based gluten‐free formulations modified with native or pregelatinised cassava starch and α‐amylase
    (Institute of food Science technology, 2010-05-26) Onyango Calvin; Mutungi Christopher; Ubehend Gunter; Lindhauer Meinolf G.
    Summary The influence of a-amylase (0–0.3 U g)1) on the crumb properties of gluten-free sorghum batter and bread, respectively, was investigated. The formulations were modified using native or pregelatinised cassava starch (i.e. batter A – 17% pregelatinised starch, 83% sorghum, 100% water fwb; batter B – 17% native starch, 83% sorghum, 100% water fwb; and batter C – 30% native starch, 70% sorghum, 80% water fwb). The batters had solid viscoelastic character with the storage modulus predominant over the loss modulus. Storage moduli of batter A decreased with increasing angular frequency, whereas the moduli of batters B and C were independent from the angular frequency. Increasing enzyme concentration did not affect the loss factors of the batters. Batters’ resistance to deformation, from highest to lowest, followed the order C > A > B. Increasing enzyme concentration decreased crumb firmness, cohesiveness, springiness, resilience and chewiness but increased adhesiveness. Overall, breads containing native starch had better crumb properties (i.e. springier and less firm, chewy and adhesive) than breads containing pregelatinised starch.
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    Effect Of Cellulose-Derivatives and Emulsifiers on Creep-Recovery and Crumb Properties of Gluten-Free Bread Prepared from Sorghum and Gelatinised Cassava Starch
    (Food Research International, 2009) Onyango Calvin; Ubehend Gunter; Lindhauer G. Meinolf
    The effect of cellulose-derivatives and emulsifiers on the creep-recovery behaviour of glutenfree dough prepared from gelatinised cassava starch and sorghum was studied. Cellulose treated doughs, except the treatment with 2.4% w/w fwb CMC, had lower resistances to deformation (range 10–33%) than emulsifier-treated doughs (range 3–13%). The higher elastic recovery of emulsifier-treated doughs corresponded to lower compliances and higher zero shear viscosities than for doughs treated with cellulose-derivatives. Addition of egg white powder (6.7% w/w fwb) eliminated several textural defects associated with gluten-free bread. Cellulose-derivatives did not decrease crumb firmness or staling rate when compared to the control. Though increasing emulsifier concentration (from 0.4% to 2.4% w/w fwb) decreased crumb firmness, crumbs treated with 2.4% w/w fwb emulsifiers, except diacetyl tartaric acid esters of mono- and diglycerides, were weak and difficult to handle after slicing. Nevertheless, all gluten-free breads treated with 2.4% w/w fwb emulsifiers staled at a slower rate than the control.
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    Rheological And Baking Characteristics of Batter and Bread Prepared from Pregelatinised Cassava Starch and Sorghum and Modified Using Microbial Transglutaminase
    (Journal of Food Engineering, 2010) Onyango Calvin; Mutungi Christopher; Ubehend Gunter; Lindhauer Meinolf G
    The effect of different concentrations (0, 0.5, 1 and 1.5 U/g) of microbial transglutaminase (MTG) on the creep-recovery properties of gluten-free batter prepared from pregelatinised cassava starch, sorghum and egg white was investigated. The test conducted in the rheometer had an instant loading of 80 Pa for 60 s and recovery of 0 Pa for 140 s. Increasing MTG concentration decreased the batters’ resistance to deformation and compliances but increased zero shear viscosity and elastic recovery. Changes in batter rheological properties were insignificant (P > 0.05) at MTG concentrations beyond 0.5 U/g. Crumb properties of gluten-free bread baked from the batter revealed that increasing MTG concentration increased (P < 0.05) crumb firmness and chewiness, whereas increasing incubation time decreased (P < 0.05) crumb cohesiveness, chewiness and resilience. There were no significant interaction effects (P > 0.05) between enzyme concentration and incubation time
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    Rheological And Textural Properties of Sorghum-Based Formulations Modified with Variable Amounts of Native or Pregelatinised Cassava Starch
    (LWT - Food Science and Technology, 2011) Onyango Calvin; Mutungi Christopher; Ubehend Gunter; Lindhauer Meinolf G.
    Sorghum bread was made from native or pregelatinised cassava starch and sorghum flour in the ratio 10:90, 20:80, 30:70, 40:60 and 50:50. The other ingredients, measured on flour-weightbasis, were water (100%), sugar (6.7%), egg white (6%), fat (2%), salt (1.7%) and yeast (1.5%). The dynamic oscillatory behaviours of the batters were affected by the amount and type of starch. In the amplitude sweep measurements, increasing concentration of native starch decreased storage modulus, whereas increasing concentration of pregelatinised starch increased the linear viscoelastic range of the batters. In the frequency sweep measurements, the loss factor of batters treated with native starch declined with increasing frequency. Batters treated with 10 or 20% pregelatinised starch showed declining loss factors, whereas batters treated with 40 or 50% pregelatinised starch showed increasing loss factors with increasing frequency. Sorghumbased batters containing native starch gave bread with better crumb properties than batters containing pregelatinised starch. Crumb firmness and chewiness declined with increasing native or pregelatinised starch concentration. Crumb adhesiveness of breads containing pregelatinised starch increased with increasing starch content but was not affected by native starch. Cohesiveness, springiness and resilience increased with increasing native starch content, but were minimally affected by increasing pregelatinised starch content.