Physical, chemical and microbiological changes in alcoholic fermentation of sugar syrup from cassava flour

Changes in alcoholic fermentation of sugar syrup produced from cassava flour with Saccharomyces cereviseae (baker’s yeast) were investigated. Cassava flour paste was hydrolysed using rice malt toproduce hydrolysate (sugar syrup), which was fermented at 28 – 30°C for 1, 2, 3, 4 and 5 days. The fermented sugar syrup was analysed for alcohol content, reducing sugars, specific gravity, soluble solids, pH, volatile acids and total acidity using standard analytical methods. Yeast growth was also monitored. Results showed that pH values decreased with increased total acidity with concomitant increase in yeast growth (biomass) and alcohol contents of the fermenting sugar syrup. There were decreases in soluble solid contents, refractive indices of the fermenting medium. Volatile acids (as acetic acids), increased with alcoholic fermentation. Fermentation of sugar syrup from cassava flour is associated with physical and chemical changes that occur in other form of fermentation alongside increased in biomass

Effects of gamma radiation on the thermoanalytical, structural and pasting properties of black rice (Oryza sativa L.) flour

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)The effects of different doses of gamma radiation on the thermoanalytical, structural and pasting properties of black rice (Oryza sativa L.) flour were studied using thermogravimetry and derivative thermogravimetry (TG-DTG), differential scanning calorimetry, X-ray diffraction (XRD), field emission gun-scanning electron microscopy (FEG-SEM) and pasting properties (RVA) analysis. The thermogravimetric curves showed four mass losses. A small displacement was observed for the second loss, which occurred for the irradiated flours, compared to the control sample. The irradiated samples showed a slight decrease in the thermal parameters: initial temperature (T (o)), peak temperature (T (p)) and gelatinisation enthalpy (a-H-3). All the black rice flours exhibited A-type crystallinity pattern, and the gamma radiation did not change the XRD patterns or the degree of crystallinity. The micro-images obtained using FEG-SEM showed a composite of organic and heterogeneous material; after gamma radiation, some changes occurred, such as cracks, pores and smaller fragments. The pasting properties decreased significantly with irradiation. The decrease in setback and breakdown viscosity after irradiation suggested an indication that it may be possible to improve the quality of food based on black rice flours. Gamma radiation can be a useful tool to modify rice flours in order to suit various functionalities and to help meet the growing demands of the food industry