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Functionality of Extrusion—Texturized Whey Proteins¹

USDA, ARS, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038

Corresponding author: C. I. Onwulata; e-mail: Conwulata{at}errc.usda.gov.

Whey, a byproduct of the cheesemaking process, is concentrated by processors to make whey protein concentrates (WPC) and isolates (WPI). Only 50% of whey proteins are used in foods. In order to increase their usage, texturizing WPC, WPI, and whey albumin is proposed to create ingredients with new functionality. Extrusion processing texturizes globular proteins by shearing and stretching them into aligned or entangled fibrous bundles. In this study, WPC, WPI, and whey albumin were extruded in a twin screw extruder at approximately 38% moisture content (15.2 ml/min, feed rate 25 g/min) and, at different extrusion cook temperatures, at the same temperature for the last four zones before the die (35, 50, 75, and 100°C, respectively). Protein solubility, gelation, foaming, and digestibility were determined in extrudates. Degree of extrusion-induced insolubility (denaturation) or texturization, determined by lack of solubility at pH 7 for WPI, increased from 30 to 60, 85, and 95% for the four temperature conditions 35, 50, 75, and 100°C, respectively. Gel strength of extruded isolates increased initially 115% (35°C) and 145% (50°C), but gel strength was lost at 75 and 100°C. Denaturation at these melt temperatures had minimal effect on foaming and digestibility. Varying extrusion cook temperature allowed a new controlled rate of denaturation, indicating that a texturized ingredient with a predetermined functionality based on degree of denaturation can be created.

Key Words: extrusion • texturization • whey proteins • functionality

Abbreviation key: WLAC = whey lactalbumin, WPI = whey protein isolate

This article has been cited by other articles:

				C. I. Onwulata, S. Isobe, P. M. Tomasula, and P. H. Cooke Properties of Whey Protein Isolates Extruded under Acidic and Alkaline Conditions J Dairy Sci, January 1, 2006; 89(1): 71 - 81. [Abstract] [Full Text] [PDF]