The level of red clover polyphenol oxidase (PPO) activity can be greatly increased following cell damage. This is probably due to activation of latent PPO by quinone products of phaselic acid produced by the constitutive active PPO, which is normally at a much lower level than the latent PPO. This “self activation” of PPO following tissue damage could act as an indicator of the level of tissue damage in a conditioned red clover crop. This study investigated a range of tissue damage levels with the PPO activation state and activation with bound-phenol formation in an attempt to correlate degree of cell damage with PPO activity.