Publication: Effect of Drying Lactic Acid Bacteria Fermented Uji on Its Pasting Properties and Content of Carboxylic Acids
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1999-01-01
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University of Nairobi
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University of Nairobi Department of Food and Nutrition Technology
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Abstract
The effect of fermentation and drying on the pasting properties and carboxylic acids of pure
flours of maize, finger millet and cassava and of composite flours of maize-finger millet and
cassava-finger millet were studied. The pasting properties were measured between 30°C and
96°C in a Brabender Amylograph while carboxylic acids from the uji slurries were determined
on thin layer chromatography plates coated with 0.25 mm silica gel. Irrespective of the treatment
given, the cereal flours of maize, finger millet and the composite of maize-finger millet
consistently had higher onset and peak gelatinization temperatures than pure cassava or the
composite of cassava-finger millet. Also the latter two flours developed higher peak viscosities
and disintegrated more rapidly after attaining the peak than either pure maize, finger millet or the
composite of maize-finger millet. The higher viscosities of the root flours was also reflected in
the higher swelling powers and solubility values at 85°C. Fermentation increased the viscosity of
the slurries. The greatest increases were recorded by maize (500BU) and the composite of maizefinger millet (780 BU). Fermentation did not affect gelatinization temperatures except for the
maize-finger millet composite whose gelatinization temperature decreased by 10°C.
Fermentation and drying resulted in increased viscosity when compared to the non-fermented
flours, except for the drum dried cassava-finger millet composite. For all the drum dried flours
there was a spontaneous increase in viscosity at 30°C when the Brabender Amylograph was
switched on. The drum dried flours absorbed about four times their own weight of water; and
since the starch granules were pregelatinized, reconstitution in cold water was difficult, as the
flour particles tended to lump together, getting wetted on the surface and inhibiting the
penetration of water into the interior. In contrast, sun and cabinet dried flours absorbed about 1.9
times their own weight of water and formed smooth slurries in cold water. Fermentation
increased total titratable acidity and fixed acidity of the slurries to about 3.9% and 3.6%
respectively, while the pH declined from 5.5 to 3.9. On drying there were no significant changes
in (p0.05) from the uji prepared from fermented and nondehydrated slurries.
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Keywords
Fermentation, Drying, Pasting properties, Carboxylic acids, Gelatinization temperatures, Viscosity