ANALYSIS OF THE IMPACT OF GUM ARABIC FROM Acacia senegal var. kerensis ON THE TECHNO-FUNCTIONAL PROPERTIES OF MAIZE AND CASSAVA FLOURS AND STARCHES

Abstract

Chemical, enzymatic, physical or natural modification of starches and flours of food crops to achieve particular, intended functional qualities is a common protocol in food processing. Unmodified flours and starches display limited functionality due to low resistance to shear stress, decomposition upon heating and high deterioration rate when subjected to different processing conditions. Hydrocolloids are currently being utilized to modify starches and flours due to the market demand for natural, safe and economical food ingredients. This study aimed at examining the the effect of utilizing gum Arabic (GA) from Acacia senegal var. kerensis on the techno-functional qualities of cassava and maize flour and starch. Milled GA powder was substituted in both starch and flour of maize and cassava at 0 %, 0.5%, 2.0 %, 4.0 %, 6.0 % and 8.0 % g/g based on dry weight. The starch/flour-gum mixtures were analyzed for pasting properties using a Brabender Viscograph-E® at 85 rpm and 700cmg torque, textural properties were measured using Texture Analyzer® and the data analysed at 95% confidence level. The findings revealed that increasing the level of GA significantly decreased peak viscosity, final viscosity, breakdown and setback values in both maize and cassava starches. However, there was no significant effect of GA on the pasting temperature 71.8-72.1oC for maize starch and 68.7-68.9oC for cassava starch. Increasing the level of GA (0 % to 8%) in both cassava and maize flours significantly decreased the peak, final and setback viscosities. The breakdown viscosity of cassava flour reduced significantly (426 to 262 BU) while maize flour recorded a zero breakdown (7.5 to 0 BU). Unlike in starches, the pasting temperature in flours significantly decreased with increasing gum levels 64.2-63.6oC and 87.1-84.9oC for cassava and maize flour respectively. The degree of gel firmness (894g) and consistency (21060gs) was significantly greater in native maize starch than in native cassava starch (89g and 2095gs respectively) however as the levels of gum increased from 0.5 to 8% there was a significant reduction on the firmness and consistency of maize starch gels as compared to cassava starch gels that showed no marked difference. Increasing the level of GA substitution in both starches significantly decreased the bulk density but significantly increased water solubility index, swelling capacity, absorption index and water holding capacity (WHC) but no significant difference was observed for WHC in both flours. These findings demonstrate that gum Arabic can be used to modify flours and starches for specific applications in the food industry. This is the first time this type of empirical data is being reported on the techno-functional properties of maize and cassava starches and flours containing GA from Acacia Senegal var kerensis