Effect of roasting and fermentation on viscosity of cereal-legume based food formulas

With the view of preparing semi-liquid weaning foods of high energy content, the influence of roasting (stationary hot air treatment) and fermentation (with natural and pure culture inocula) on the viscosity of maize-sorghum-soya porridges was investigated. Roasting resulted in porridges of significantly higher viscosity (cooked porridge cooled to 40 degrees C). Porridges made from the individual ingredients (maize, sorghum, soya) did not show this behaviour. Natural fermentation of mixed ingredients resulted in lower porridge viscosities (cooked porridge cooled to 40 degrees C, as well as hot-paste peak viscosity) when pH was 5.0-5.5. At lower pH the viscosity of the final porridges increased. Fermentation experiments of individual ingredients inoculated with pure cultures of Lactobacillus plantarum and Candida famata lead to the conclusion that various factors contribute to the effect of fermentation on porridge viscosity. Porridges of minimum viscosity are obtained at pH 5.0-5.5 corresponding with a moderate extent of fermentation. From a consumer safety point of view, it would be preferable to acidify to lower pH values (pH < 4.5). If necessary, viscosity adjustments could be made using malted cereals.