Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/2003
Publication Date: 11/15/2003
Citation: Onwulata, C.I., Tomasula, P.M. 2003. Functionality of extrusion-texturized whey proteins. Journal of Dairy Science. 86:3775-3782.
Interpretive Summary: Most crunchy snack foods are made from corn meal in a machine called an extruder. The extruder consists of a long, heated barrel with two mixing screws inside. The corn meal is cooked as the screws mix and push the corn meal through the extruder to form the snack food. The crunchiness of the snack is determined by its moisture content and its temperature as it leaves the extruder. To improve the nutritional profile of crunchy snack foods, whey proteins, whey protein isolate (WPI), whey protein concentrates (WPC), or whey albumin (WLA) - concentrated forms of whey - were extruded with corn meal. It was determined that addition of WPI adversely affected the crunchiness, color, and texture of extruded snack foods. Extrusion conditions that modify WPI, WPC and WLA, before it is added to extruded corn, were then determined. The temperature and moisture conditions of the WPI, WPC, or WLA leaving the extruder were adjusted to modify their structures. This then created a form of WPI, WPC or WLA compatible with that of the corn meal. This knowledge allows the creation of nutritious expanded crunchy snack foods, and utilizes whey protein; a byproduct of the cheesemaking process.
Technical Abstract: 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 is utilized in foods. In order to increase their utilization, texturizing WPC, WPI, and whey albumin (WA) 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 (WA) were extruded in a twin screw extruder at approximately 38% moisture content (15.2 mL/min, feed rate 25 g/min) and using four melt temperatures at the die 35, 50, 75, and 100 degrees C respectively. Protein solubility, gelation, foaming and digestibility were determined for the products. Degree of denaturation, determined by solubility at pH 7, for extruded WPI increased from 30 to 60, 85, and 95% for melt temperatures of 35, 50, 75, and 100 degrees C, respectively. Gel strength of extruded isolates increased initially 115% (35 degrees C) and 145% (50 degrees C), but all gel strength were lost after 75 degrees C. Denaturation at these melt temperatures had minimal effect on foaming. Similar results were obtained for extruded WPC and WA. Varying melt temperature at the extruder die allowed a controlled rate of denaturation, indicating that a texturized ingredient with a predetermined functionality based on degree of denaturation can be created.