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Fermented Sorghum as a Functional Ingredient in Composite Breads

¹Department of Rural Engineering, Faculty of Agronomy and Forestry Engineering, Eduardo Mondlane University, Maputo, Mozambique. ²Soil and Crop Sciences Department, Cereal Quality Laboratory, Texas A&M University, College Station, TX. ³Department of Food Science, University of Pretoria, Pretoria, South Africa. ⁴Corresponding author. E-mail: jtaylor@postino.up.ac.za. Phone: +2712-420-4296. Fax: +2712-420-2839.

Whole sorghum flour was fermented (a five-day natural lactic acid fermentation) and dried under forced draught at 60°C, and evaluated for its effect on sorghum and wheat composite bread quality. In comparison with unfermented sorghum flour, fermentation decreased the flour pH from 6.2 to 3.4, decreased total starch and water-soluble proteins, and increased enzyme-susceptible starch, total protein, and the in vitro protein digestibility (IVPD). Fermentation and drying did not decrease the pasting temperature of sorghum flour, but slightly increased its peak and final viscosity. In comparison with composite bread dough containing unfermented sorghum flour, fermented and dried sorghum flour decreased the pH of the dough from 5.8 to 4.9, increased bread volume by ≈4%, improved crumb structure, and slightly decreased crumb firmness. IVPD of the composite bread was also improved. Mixing wet fermented sorghum flour directly with wheat flour (sourdough-type process) further increased loaf volume and weight and reduced crumb firmness, and simplified the breadmaking process. It appears that the low pH of fermented sorghum flour inactivated amylases and increased the viscosity of sorghum flour, thus improving the gas-holding capacity of sorghum and wheat composite dough. Fermentation of sorghum flour, particularly in a sourdough breadmaking process, appears to have considerable potential for increasing sorghum utilization in bread.