PPO activity of two varieties of pears. Control of enzymatic browning for temperature effect, presence of inhibitors and complexation with b-cyclodextrin

Polyphenoloxidase (PPO) is an enzyme that produces enzymatic browning, which causes numerous losses in the industry. For this reason, the characterization and inhibition of PPO are very important. In this work were characterized PPOs from two types of pears (Pyrus communis L): White of Aranjuez (APPO) and Williams (WPPO), since this comparison has not been done before. The optimum pH and temperature for enzyme activity were determined (APPO: 7 and 30ºC; WPPO: 7.5 and 24.5ºC). Both enzymes are heat-labile enzymes and exhibited similar behaviour against temperature. The enzymes analysed showed a higher affinity for 4-methylcatechol than for catechol. The inhibition of PPOs through ascorbic acids, 4-hexylresorcinol, sodium isoascorbate and citric acid was determined. Additionally, the inhibitory effect of b-Cyclodextrin, which results in the prevention of fruit oxidation because it forms an inclusion complex with the substrates, was evaluated. The value of the constant of the complex formed was 16888 M-1.

Keywords: polyphenoloxidase, chemical inhibition, b-Cyclodextrin, inclusion complex.