17B-5 |
|
M. K. WALSH, D. P. Taylor, and C. E. Carpenter. Dept. of Nutrition & Food Sciences, Utah State Univ., UMC 8700, Logan, UT 84322-8700 Whey protein can be extruded into expanded and textured products using a patented process. Still, there is a general lack of understanding regarding how protein functionality influences the properties of the extruded product. To expand our knowledge base in the area, we evaluated and compared functional properties and extrusion performance of whey protein concentrate after sulfonation to disrupt disulfide bonds to various degrees. Whey protein concentrate (WPC) was treated with sodium sulfite to achieve 4 levels of disulfide bond sulfonation (0, 31, 54, and 71%), and functionality of each was evaluated by measuring emulsification activity index (EAI), foam stability, foam overrun, gel strength, and protein melt temperature. Each sulfonated WPC was blended with cornstarch and extruded into an expanded product. Extrudates were analyzed for physical (air cell diameter, expansion ratio, breaking strength, and density) and chemical (water adsorption index (WAI), water solubility index (WSI), moisture content, soluble protein and soluble carbohydrate) properties. Sulfonation increased foam overrun, foam stability, and EAI, while protein melt temperature decreased. Changes in functionality were attributed to increased protein flexibility from unfolding and from increased electrostatic charges from the added sulfite groups. Extrudates from control and 54% sulfonated WPC had larger expansion ratios and air cell diameters and smaller densities and breaking strengths than extrudates from the 31 and 71% sulfonated WPC. EAI of sulfonated WPCs correlated to all the chemical and physical properties of their extrudates except WAI, WSI and breaking strength. Foam stability of sulfonated WPCs correlated to all the chemical and physical properties of their extrudates except WAI, WSI, soluble carbohydrate, moisture and expansion. In summary, the disulfide bond content of whey proteins influenced both their functional properties and the chemical and physical properties of their extrudates. There was a positive correlation between extrusion performance of WPC and its functional properties reflecting flexibility.
Session 17B, Dairy Foods: General
|