59D-10 |
Characterization of binding interaction of a model phenolic compound (para-Hydrobenzoic Acid) with dairy proteins |
S. K. BAIER1, D. J. McClements1, and K. Shetty2. (1) Food Colloids and Bioploymer Lab, University of Massachusetts, 430 Chenoweth Laboratory, Amherst, MA 01003, (2) Laboratory of Food Biotechnology, University of Massachusetts, Chenoweth Laboratory, Amherst, MA 01003 In recent years the importance of certain phenolic compounds as antimicrobial, antioxidant and nutraceutical agents has been established. The bioavailability and neutraceutical effects of many phenolic compounds are modified in the presence of proteins. To obtain the maximum benefit of these phenolic compounds, it is of fundamental importance to understand the nature of the protein - phenolic interaction. Our objective was to use a variety of modern analytical techniques to systematically study the nature of the protein - phenolic interactions. An isothermal titration calorimeter was used to monitor the enthalpy of mixing of a model phenolic compound (para-hydrobenzoic acid, p-HBA) with different purified dairy protein fractions (a-lactalbumin, b-lactoglobulin, b-casein and BSA) at different temperatures (20 to 50 oC) and pH values. (3-9). The thermodynamic binding parameters (binding constant and number of binding sites) of selected protein – phenolic combinations was quantified using equilibrium dialysis. The binding of p-HBA to dairy proteins was weak (K < 103) and exothermic. The binding enthalpy became increasingly exothermic in the following order: a-lactalbumin > b-lactoglobulin > b-casein > BSA. We hypothesize that the origin of the interaction was partly hydrophobic and partly electrostatic, which accounts for its dependence on protein surface area and surface chemistry. This study has provided quantitative information about the binding of a model phenolic compound to the major dairy proteins. A better understanding of the nature of these interactions would enable food scientists to optimize the bioavailability of these nutraceutical compounds in the human diet.
Session 59D, Food Chemistry: Proteins and Physicochemical Properties
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