The Effect Of Modified Starches On The Rheological And Baking Properties Of Wheat/Maize, Wheat/Millet Composite Flours For Biscuit Production

ABSTRACT

The effect of modified starches on the baking properties of composite (wheat- maize, wheat-millet) flours was investigated. Starches were produced from sorghum, maize, and cassava. The starches were modified chemically using 1.0% hydrochloric acid, glucoamylase and a combination of 1%l-lcl and glucoamylase. The bulk density, least gelation concentration, solubility in water, swelling index and water absorption capacity of the modified and unmodified starches were determined. The effect of these starches on dough made from wheat/maize, wheat/millet composite flours (75:25) were also investigated using a farinograph. Based on the results from the farinograph studies, sensory evaluation was carried out on wheat-millet flour with varying concentrations of acid treated sorghum starch. The biscuits were also subjected to further tests to determine their physical properties such as spread ratio, percentage shrinkage and moisture absorption. The yields of the starches were 15.59%, 54.14% and 56.71% for cassava, maize and sorghum respectively. The percentage recovery for modified starches from various treatments was all above 70% with cassava starch having the best recovery for all the treatments. There were no significant differences (p> 0.05) in the bulk densities, swelling index and water absorption capacities of the starch samples. However, maize starch treated with a combination of acid and enzyme had the highest solubility in water of 47%, while sorghum starch treated with 1 % Hcl had the highest LGC value of 15%w/v. the dough from wheat/millet composite flour (75:25) with 5% Ass incorporated into it proved to be the best flour for biscuit making, with a water absorption rate of 59.90, dough development time (DDT) of 1 .5, stability 4.5 minutes. Biscuits baked with 1% Ass and wheat millet flour proved to be best as it improved the organoleptic properties of the wheat/millet biscuits.