Browsing by Author "Hofmann Thea"

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    Digestibility and Antinutrient Properties of Acidified and Extruded Maize–Finger Millet Blend in the Production of Uji
    (ScienceDirect, 2004) Onyango Calvin; Noetzold Horst; Ziems Annette; Hofmann Thea; Bley Thomas; Henle Thomas
    Lactic and citric acids were used as alternatives to backslop fermentation in the manufacture of extruded uji (a thin porridge from eastern Africa). Acidity of the blends was reduced by fermentation or progressively lowered with 0.1, 0.5 and 1.0 mol/l lactic or citric acids before extrusion. The absence of ethanol soluble starch in the extrudates indicated that extrusion solubilizes starch without formation of maltodextrins. In vitro starch digestibility increased from 20 mg maltose/g starch in the raw blend to about 200 mg/g after extrusion. Extrusion reduced total dietary fibre by 39–68%, redistributed soluble to insoluble fibre ratios and had a negligible effect on the formation of resistant starch (less than 1 g/100 g). In vitro protein digestibility increased after fermentation or acid treatment followed by extrusion. Nitrogen solubility index decreased by 40–50% when the unfermented, lactic or citric acid treated blends were extruded, but increased by 20% when the blend was fermented before extrusion. Amino acid analysis showed that histidine, lysine and arginine contents were lowest in the fermented-extruded blends. Tannin content decreased from 1677 mg/100 g in the raw blend to between 551 and 1093 mg/100 g in the extrudates whereas phytate content remained unaffected by extrusion (248–286 )
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    Production of High Energy Density Fermented Uji using a Commercial Alpha-Amylase orby Single-Screw Extrusion
    (ScienceDirect, 2003) Onyango Calvin; Henle Thomas; Hofmann Thea; Bley Thomas
    The effects of alpha-amylase and extrusion on the viscosity and energy density of uji, a spontaneously fermented thin porridge from different combinations of maize, finger millet, sorghum and cassava, were investigated. Fermentation alone was not able to reduce the viscosity of uji, but addition of 0.1–2.1 ml/100 ml alpha-amylase to the fermented slurry or extrusion of the fermented and dried flour at 150–180°C and a screw speed of 200 rpm reduced the viscosity of 20 g/100 ml uji from 6000–7000 to 1000–2000 cP, measured at 40°C and a shear rate of 50 s−1. The amount of flour required to make uji could thus be increased by a factor of 2.0–2.5 and consequently it was possible to produce uji with acceptable energy densities (0.6–0.8 kcal/g) for child feeding.