Effects of sourdough-type fermentation and sorghum type on the techno-functional properties of the batter used for kisra, a fermented flatbread

Techno-functional properties of six sorghum types were determined during spontaneous sourdough batter-type fermentation for Kisra production. All sorghum types showed a progressive decrease in pH to about 3.3 with fermentation for 40 h, accompanied by an increase in titratable acidity and free amino nitrogen. Fermentation increased pasting viscosity at 16 and 24 h, but decreased at 40 h due to starch hydrolysis. Protein hydrolysis as shown by SDS-PAGE leads to disaggregation of flour particles and the release of starch granules to increase the pasting viscosity. Thus, starch was more freely available to absorb water to paste and produce a higher viscosity from zero to 40 h. The decrease in pasting viscosity from 24 h to 40 h of fermentation was related to starch hydrolysis, as there was a reduction in total starch in the batter and pitting of starch granules, as shown by scanning electron microscopy. Fermentation had a more significant effect on techno-functional properties than sorghum types. Low protein and high tannin contents among the sorghum type also showed higher pasting viscosity. The techno-functional changes of sorghum batter during fermentation, especially the high pasting viscosity, might be helpful for structure design of kisra and other gluten-free sorghum-based products.