it was observed that WWF with finer millfeed particles exhibited significantly higher PPO activity than that with coarser millfeed particles (P < 0.05). PPO and phenolic compounds are primarily located in the cell plasmid of wheat bran layer so the results are probably attributed to the fact that fine grinding of millfeeds promotes the exposure of PPO active sites by fracturing cell walls in bran and provides more opportunity for PPO to access enzyme substrates. Polyphenol oxidase (PPO) has been implicated as a leading cause of discoloration in fresh noodles and other wheat products.