59D-16 |
Hydrophobic binding properties of high pressure treated b-lactoglobulin affected by pH, NaCl, KIO3 and N-ethylmaleimide |
J. YANG1, J. R. Powers1, K. A. Dunker2, S. Clark1, and B. G. Swanson1. (1) Department of Food Science and Human Nutrition, Washington State University, P.O. BOX 646376, Pullman, WA 99164-6376, (2) Department of Biochemistry and Biphysics, Washington State University, Pullman, WA 99164 The molten globule is an intermediate structural state of protein between the folded and fully unfolded states possessing a unique hydrophobic structure with potentially advantageous functional properties. b-lactoglobulin (b-Lg) is induced into the molten globule state by high hydrostatic pressure (HHP) and stabilized by intermolecular disulfide bonds. HHP treatment conditions directly affect the observed hydrophobicity of b-Lg in the molten globule state. Our objective was to investigate the effects of pH, NaCl, KIO3 and N-ethylmaleimide (NEM) during HHP treatment on the hydrophobic affinity of b-Lg. b-Lg solutions (27µM) at selected pH, NaCl, KIO3 or NEM concentrations were treated at 600 MPa at 50°C for 16 min. Fluorescence intensity of 1-anilino-naphthalene-8-sulfonate (ANS) was used to assess hydrophobicity of b-Lg. b-Lg treated with HHP at pH 7.0 exhibited a 1.9X or 1.1X greater ANS fluorescence intensity than b-Lg treated at pH 2.0 or 9.0. ANS fluorescence intensity of b-Lg increased when treated in the presence of NaCl and KIO3. b-Lg treated with HHP at pH 7.0 in 0.16M NaCl or 0.2mM KIO3 exhibited a 1.5X increase of ANS fluorescence intensity. Addition of NaCl after HHP treatment of b-Lg solutions increased ANS fluorescence intensity. With the addition of 0.8M NaCl, HHP treated b-Lg with or without KIO3 exhibited a 5.0X or 4.2X increase of ANS fluorescence intensity when compared to native b-Lg. b-Lg treated with HHP in the presence of NEM resulted in a 2.2X increase in ANS fluorescence intensity when compared to the ANS fluorescence intensity of HHP treated b-Lg containing no NEM. The molten globule state of b-Lg induced by HHP at pH 7.0 exhibited greater hydrophobic affinity than b-Lg treated with HHP at pH 2.0 or 9.0. Addition of NaCl and KIO3 to b-Lg during or after HHP treatment at pH 7.0 may improve hydrophobic functional properties of whey proteins.
Session 59D, Food Chemistry: Proteins and Physicochemical Properties
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