Effect of chemical agents on physical and rheological properties of starch-guar gum extrudates

A mixture of starch and guar gum was extruded with citric acid, sodium stearoyl-2-lactylate (SSL) and diacetyl tartaric acid ester of monoglyceride (DATEM). Water solubility, blue value, extrudate expansion and viscosity were measured for the different additives. Incorporation of hydrocolloids caused a synergistic increase in viscosity indicating a strong interaction between starch amylose and gums. Extrusion with chemical agent affected the physical properties of starch. Citric acid decreased viscosity and increased water solubility and expansion volume. Sodium stearoyl-2-lactylate and diacetyl tartaric acid ester of monoglyceride increased viscosity while reducing expansion and water solubility. This indicated that even at extrusion temperatures, these surfactants maintained their complexing power. Analysis of variance showed that addition of chemical agents significantly affected the physical and rheological properties of the extrudates.