Electron Spin Resonance (ESR) or Electron paramagnetic resonance (EPR) is a unique and sensitive technique for detection of radical formation and antioxidant properties. Small sample amount (mg) is necessary and typical requires no to very limited sample preparation.

• ESR detects paramagnetic compounds (i.e. free radicals and transition metal ions)
• Used to study the early oxidative changes in various food systems (radical formation)
• Small amount of sample is placed in a strong magnetic field where paramagnetic compounds such as radicals absorb microwave energy due to the transition of unpaired electrons  --> we get a signal