Physicochemical Interactions Between Aroma Compounds and Milk Proteins: Effect of Water and Protein Modification

¹ Université Cadi Ayyad, Faculté des Sciences Semlalia, Marrakech, Morocco
² Ecole Nationale Supérieure de Biologie Appliquée à la Nutrition et à l'Alimentation, Université de Bourgogne, 21,000 Dijon, France
³ Faculté des Sciences Mirande, Université de Bourgogne, 21,000 Dijon, France

The physicochemical interactions between aroma compounds and sodium caseinate were studied by complementary techniques involving the protein in aqueous solution at 25 or 75 g/L (exponential dilution and equilibrium dialysis) or in a solid state (sorption and infrared spectroscopy). No retention of acetone, ethyl acetate, and 2-propanol in aqueous solutions was found by exponential dilution and equilibrium dialysis. Diacetyl and benzaldehyde interacted with sodium caseinate through strong and weak bonds, as found by equilibrium dialysis. The results obtained by sorption differ from those obtained in aqueous solutions. The compounds that sorbed best to sodium caseinate were acetone and ethyl acetate, and their infrared spectra showed a negative shift of the carbonyl peak between the pure and sorbed state of the compounds, demonstrating their involvement in hydrogen bonds with the protein. In addition, 2-propanol and ethyl acetate were strongly bound to sodium caseinate in a dried state. For the other compounds, results from infrared spectroscopy indicated the presence of interactions between sodium caseinate and the ligand.

Key Words: aroma • casein • water • interactions

Submitted on July 23, 1996
Accepted on July 9, 1997