Measurement of the oxidation-reduction potential of cheddar cheese

The objective of this study was to develop a method to measure the oxidation-reduction (redox) potential of hard cheeses such as cheddar and to investigate the impact on this parameter of measurement temperature, and factors associated with electrochemical cell design such as distance between reference and working electrodes and depth into the cheese of the platinum electrodes. For this purpose, a novel, self-sealing, platinum working electrode was constructed which was thin and flexible enough to be inserted directly into the cheese sample. A calomel electrode was used as the reference electrode and the circuit was completed with a 3 M KCl salt bridge. The physical orientation of electrodes, such as distance between reference electrode and working electrode, had a substantial effect on equilibrium time for redox potential measurement. The time required for redox potential to reach equilibrium was 2 d in cheddar cheese and the optimum distance between the platinum and calomel electrodes was 2.5 cm. The fastest equilibration time was obtained when the working electrode was inserted 5 or 6 cm into the cheese. Temperature also had an important effect on redox potential. The shortest time to reach equilibrium of potential was at room temperature (20 degrees C), but it was not practical to keep cheese at this temperature for a period of 2 d. Therefore, redox measurement at 12 degrees C was recommended in spite of the longer equilibration time compared with room temperature. The results of this study suggest that the novel platinum working electrode allows reproducible measurement of the oxidation-reduction potential of cheddar cheese.