Submitted to: Journal of Food Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/2006
Publication Date: 3/3/2007
Citation: Nalesnik, C.A., Onwulata, C.I., Tunick, M.H., Phillips, J.G., Tomasula, P.M. 2007. Drying properties of extruded whey protein concentrates and isolates. Journal of Food Engineering. 80: 688-694.
Interpretive Summary: Drying is often an essential process for the preparation of food materials. Drying is used to reduce the moisture content of foods for reasons such as: preservation, safety, ease of processing, and consumer appeal. New food materials were invented at ARS which can be used to increase the protein content of snack foods for better nutritional value. They are called extruded whey protein concentrates (WPC) and extruded whey protein isolates (WPI). When new materials become available, it is necessary to understand how important properties of the material, such as color, density, and texture (how the material feels and breaks), are affected by drying. In this study, extruded WPC and WPI were dried at 40oC and 70oC for up to 210 minutes. The color of these materials did not change when dried at these conditions. The density, or weight of material in a certain volume, increased slightly with drying for extruded WPC at 40oC and 70oC and for extruded WPI at 70oC. Measurements of texture showed a difference at a drying time of 90 minutes and moisture of about 20% to 25% for extruded WPC and WPI. Appropriate drying conditions can now be used by processors to achieve the desired color, density, and texture of extruded whey protein, depending upon the particular use.
Technical Abstract: 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 40oC and to a final moisture of about 14% w.b. at 70oC. Color, density, and texture measurements were made as a function of drying time. No significant change in color was observed at 40oC or 70oC for either material as it dried. Density increased slightly with drying time for extruded WPC at 40oC and 70oC, and extruded WPI at 70oC. Texture, measured as linear distance, increased in magnitude with drying time. Significant differences (p<0.05) in texture at a drying time of 90 minutes, 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.