Effect of drying lactic fermented uji (an East African sour porridge) on some carboxylic acids

Abstract

Maize, finger millet, cassava, maize–finger millet and cassava–finger millet flours were fermented and sun-, cabinet-, or drum-dried. Total titratable acidity (TTA), fixed acidity (FA), pH and carboxylic acids were determined. The TTA of the non-fermented flours ranged from 0.22%(w/w) lactic acid in cassava to 0.36%(w/w) lactic acid in the maize–finger millet composite. After fermentation the TTA ranged from 3.26%(w/w) lactic acid in cassava–finger millet to 4.54% in maize-finger millet while FA ranged from 2.86% in cassava–finger millet to 4.26% in cassava and maize–finger millet. Fermentation decreased the pH from about 5.5 to 3.7–4.1. Drying did not change the pH but TTA decreased by 20–60%. Acetic acid levels in the fermented slurries varied from 0.80 to 0.95 µg per 5 µg while those of hexanoic acid varied from 0.9 to 1.8 µg per 5 µg. Propionic acid was absent in the fermented slurries. Acetic and formic acids were completely lost when the fermented slurries were dried. On average hexanoic acid losses on drying varied from 33% in maize to 91% in cassava fermented slurries. These losses were not significantly influenced by the drying system. In sensory evaluation panellists could not detect flavour loss as a result of drying.