The effects of drying on the properties of extruded whey protein concentrates and isolates Original Research Article

Extruded whey protein concentrate (WPC) and extruded whey protein isolate (WPI) are new food materials that may be used to fortify foods, and as such, the effects of drying on their physical properties need to be investigated for efficiency in milling and blending. Extruded WPC and extruded WPI at an initial moisture content of about 30% w.b. and 37% w.b., respectively, were dried to a final moisture of about 21% w.b. at 40 °C and to a final moisture of about 14% w.b. at 70 °C. Color, density, and texture measurements were made as a function of drying time. No significant change in color was observed at 40 °C or 70 °C for either material as it dried. Density increased slightly with drying time for extruded WPC at 40 °C and 70 °C, and extruded WPI at 70 °C. Texture, measured as linear distance, increased in magnitude with drying time. Significant differences (p < 0.05) in texture at a drying time of 90 min, corresponding with a moisture of about 20% w.b. to 25% w.b. for extruded WPC and extruded WPI, were observed. Such a transition in texture may indicate that drying to a moisture of 20% w.b. to 25% w.b. is adequate for extruded whey proteins.