FLOW BEHAVIOR AND FUNCTIONAL PROPERTIES OF MALT EXTRACT CONCENTRATES

Abstract

Flow characteristics and functional properties of malt extract concentrates were investigated. Flow behavior was studied using a coaxial viscometer over shear rates of 0.6–145.8 s‐1. The shear rate‐shear stress data followed the power law, Casson, Herschel‐Bulkley and Bingham plastic models. Herschel‐Bulkley values for flow behavior index which ranged from 0.73–0.94, and presence of yield stress indicated the Bingham plastic nature of malt extract concentrates. The activation energy of flow for various concentrates was in the range of 14.8–17.7 kcal/gmole. Magnitudes of Reynold numbers (0.0–49.9) for all concentrates were lower than 2100. Temperature, yield stress and plastic viscosity considerably influenced the flow of concentrates in straight pipes. The pressure drop and power requirements for flow of concentrates in pipes at 50°–60°C were lower than those at 30°C, but negligibly different from those at 80°C. Coefficients of correlation between the Bingham plastic values for pressure drop and yield stress (r = 0.86, P < 0.01), and plastic viscosity (r = 0.97, P < 0.01) were highly significant. Hulled barley and corn concentrates containing high amounts of reducing sugars, showed low viscosities and yield stresses, and required desirably low power for flow in pipes at 50°–60°C. The high protein concentrates of wheat and triticale malts showed high whip volume and good foam stability. Wheat concentrate was superior in fermentability. Hulless barley and finger millet malts produced concentrates with high viscosities which might facilitate their utilization in gums, candies and other such products.