Comparison of the characterization and the temperature/pressure stability of soluble and membrane-bound polyphenol oxidase from 'Lijiang' snow peach

摘要

The characterization of soluble polyphenol oxidase (sPPO) and membrane-bound (mPPO) from 'Lijiang snow' peach was compared, and the inactivation effects by thermal treatment ranging from 45 to 85 degrees C and highpressure processing at 550 MPa for 10-50 min were investigated. sPPO and mPPO both showed optimum activity at pH 7.0, while another optimum pH at 5.0 was observed for mPPO. The optimum temperatures for sPPO and mPPO were 30 degrees C and 50 degrees C, respectively. The optimum substrate of sPPO was caffeic acid, while mPPO showed the highest activity against 4-methylcatechol. All inhibitors showed poorer inhibitory effects on mPPO compared with sPPO. According to kinetic parameters, sPPO and mPPO were well described by the first-order model and the fractional-conversion model, respectively. The activity of sPPO was activated after HPP at 550 MPa for 20-50 min, while mPPO was more stable under the treatment conditions investigated.