Nutritional and microbiological attributes of soybean(Glycine max) during fermentation with Rhizopus oligosporus

Soybeans (Glycine max) which belong to the family leguminosae constitute one of the oldest cultivated crops of the tropics and sub-tropical regions, and one of the world’s most important sources of protein and oil.  It is being used because of its good quality and functionality of its proteins, surplus availability and low cost. In this study, a mold Rhizopus oligosporus was used to ferment soybean, and the time course (12 h for 3 days) of changes in its characteristic was observed in order to investigate the period of maximum changes, and the consequent effect on nutritional benefits. Proximate composition, vitamins, mineral contents and microbiological characteristics were determined using standard procedures. Results obtained revealed that fermentation for 36 h produced optimal changes (p < 0.05) in terms of the contents of protein, ash, fibre, fat, moisture and carbohydrate.  Low levels of moisture and carbohydrate contents of fermented soybean flour with increase in fermentation period were obtained while vitamins A, B2 and niacin increased significantly (p < 0.05). Significant increases were also observed with respect to values of the mineral elements. Microbiological analyses indicated that no faecal coliforms were detected, although the populations of other groups of microorganisms increased significantly within the period of fermentation. Therefore, the study has demonstrated a desirable use of Rhizopus oligosporus in order to obtain fermented product of soybean which could be used to fortify starchy foods. Keywords: Fermentation, soybean, Rhizopus, nutritional and microbiological attribute

Effect of Heat-Moisture Treatment on Equilibrium Moisture Content Models for Cassava Starches

The level of water contained in food products is known to affect several unit operations in food processing including drying, storage, and thermodynamics phenomena which are related to the sorption attributes of food. Heat-moisture treatment as an aspect of the thermodynamic properties of the food affects sorption phenomena and invariably the associated empirical models for the sorption behaviour. In this study, effect of heat-moisture treatment on sorption moisture isotherms for cassava starch at 27, 32, and 37oC, respectively was determined for selected cassava genotypes (TMS 97/4763 and TMS 98/0510) including its impact on equilibrium moisture content (EMC) empirical models. The moisture isotherms were sigmoidal indicating effect of temperature and show the influence of the heat pre-treatment. Six widely recommended three parameters sorption models were fitted to the EMC data from the gravimetric method. Desorption isotherms appears well fitted than adsorption isotherms. Analysis shows that due to the heat-moisture treatment, the Modified Oswin Equation (MOE) and Modified Halsey Equation (MHE) models are the preferred empirical equations for the modelling of the emc data for the cassava starches. Keywords: Cassava starch, equilibrium-moisture-content, heat-moisture treatment, sorption, isotherms

Effect of drying conditions on energy utilization during cocoyam drying

Cocoyam samples soaked in sodium metabisulphite (SM) and water blanched (WB) were oven dried at 50, 60 and 70° C and microwave power levels of 385, 540 and 700 W while untreated samples were sun dried. The effect of drying on selected properties of cocoyam was studied. The drying time generally reduced with increase in drying temperature and power level used. The use of SM pretreatment resulted in lower drying times compared with WB pretreatment. Effective moisture diffusivity values (Deff) for all the drying conditions varied from 5.27 x 10-8 to 2.07 x 10-6 m2/s and SM samples had higher values than WB samples.  Activation energy values for oven drying were 37.41 KJ/mol and 61.79 KJ/mol and that for microwave drying were 38.59 and 41.91W/g for SM and WB samples respectively.  The energy consumption varied from 125.1 to 142.8 kWh and 308 to 396.7 Wh while that of specific energy requirement varied from 86.2 to 106.5 kWh/kg and 1.49 to 2.03 KJ/kg water for oven drying and microwave drying respectively