Differential inhibitory effects of organic acids on pear polyphenol oxidase in model systems and pear puree

Abstract

The inhibitory effects of ascorbic, citric, ferulic and salicylic acid on pear polyphenol oxidase (PPO) were investigated in model and food system. All four organic acids showed strong inhibition effect in model system. However, compared to model system, inhibitory effect of PPO in pear puree was quite different. Ascorbic acid showed a much weaker effect in pear puree compared to the model system. Similarly, ferulic and salicylic acid had limited inhibitory effect in pear puree. Interestingly, the inhibition of PPO activity was not correlated to browning control in pear puree. Ascorbic acid in low concentration was not effective in inhibiting PPO activity in pear puree but exhibited an excellent anti-browning effect. The study indicates that the level of PPO activity is not always a good indicator of susceptibility to browning in foods. Overall, ascorbic acid showed the strongest inhibition of browning and increased the total phenolic content of pear puree.