Mild‐thermal and high pressure processing inactivation kinetics of polyphenol oxidase from peach puree

Abstract

This study has investigated the inactivation of polyphenoloxidase (PPO) in peach puree during thermal (50–60 °C, 2–30 min) and combined high pressure‐mild thermal treatment (HPMT) (200–600 MPa, 25–45 °C, and 2–23 min). HPMT resulted immediately after treatment in an increase in PPO activity up to 66.50% at 200 MPa and 45 °C compared with the untreated samples. The reaction order (nth) of PPO thermal inactivation was 1.951 (0.1 MPa, 50–60 °C) and 0.953 for the HPMT treatment (200–600 MPa, 25–45 °C). Fractional kinetic models were applied in PPO thermal (~89% labile fraction, 11% stabile fraction) and HPMT inactivation (up to ~67% stabile fraction at 200 MPa, 25 °C). The activation energy estimated for the thermal inactivation in 50–60 °C range at 0.1 MPa was 148.26 kJ/mol, while for the HPMT inactivation varied from 82.31 kJ/mol at 300 MPa to 226.16 kJ/mol at 500 MPa. A third order polynomial model described the PPO inactivation by HPMT. Practical application Inactivation of polyphenoloxidase (PPO), enzyme responsible for browning is a mandatory condition for maintaining quality of the processed fruits. As this enzyme is generally known to display variable thermal and/or barostability, depending on the type of food matrix, kinetic data are required to optimize the processing parameters. The data on peach puree PPO and the models provided in the current study could help producers to identify the optimum peach processing condition necessary for the inactivation of PPO by high pressure‐mild thermal treatment, leading to the extension of puree shelf life. However, methods for limitation of the oxygen presence in the peach puree mixtures should also be employed during processing and storage.

Quality and Stability Equivalence of High Pressure and/or Thermal Treatments in Peach–Strawberry Puree. A Multicriteria Study

“…The current study found a more labile PPO compared to other studies performed in strawberry or peaches alone [8,25]. After two weeks of storage the activity of PPO in the TT sample was reactivated to a value two-fold higher than in the first day after the treatment.…”

“…The PPO activity was determined according to the method described by [8]. Briefly, to determine PPO activity, 0.350 mL of extract was mixed in 1.420 mL McIlvaine buffer (pH 6.6) and 0.730 mL 0.175 M pyrocatechol was added.…”

“…In another study performed by researchers [6] strawberry PPO was found to be highly resistant to HPMT at 600 MPa, 60 • C for 10 min, with a residual PPO activity in the processed samples of approximately 71.8% (600 MPa, 60 • C, 10 min). However, a study conducted on HPP peach pure indicated that PPO was susceptible to inactivation, after the HPMT treatment at 600 MPa, 50 • C for 10 min when the residual activity was of approximately 30% [8]. The differences reported in residual activity of PPO from fruits after high pressure and/or thermal treatments is influenced by fruit species and cultivars and in some cases, by the presence of latent enzymes that are released during processing [8,25].…”

“…However, a study conducted on HPP peach pure indicated that PPO was susceptible to inactivation, after the HPMT treatment at 600 MPa, 50 • C for 10 min when the residual activity was of approximately 30% [8]. The differences reported in residual activity of PPO from fruits after high pressure and/or thermal treatments is influenced by fruit species and cultivars and in some cases, by the presence of latent enzymes that are released during processing [8,25].…”

“…Fruit purees' shelf-life can be extended by traditional thermal treatment (TT), which usually determines undesirable appearance changes, flavor and nutritional losses of the final product or by alternative treatments, such as high pressure processing (HPP), which proved to be a successful commercial solution with minimal negative effects on the overall quality of liquid or solid foods [3,4]. Nevertheless, application of HPP alone is not a magic bullet, as it usually does not completely inactivate the activity of browning related enzymes mainly responsible for deleterious effects in fruits: no peroxidase (POD) inactivation at pressures lower than 800 MPa in Reineta apple slices [5], 40% POD inactivation in strawberries of three cultivars after HP treatment at 600 MPa, 20 • C, for 5 min [6], 26% POD inactivation in pears treated at 600 MPa, 20 • C, for 5 min [7]; 35% inactivation of polyphenoloxidase (PPO) in peach puree after HPP at 600 MPa, 25 • C for 5 min [8], 70% PPO inactivation in pear slices after 600 MPa, 20 • C for 5 min [7], and only 7% PPO inactivation in apple, orange, strawberry and banana smoothie after 600 MPa, at 10 • C, for 3 min [9]. Limited information is available on fruit spoilage yeasts and fungi survival and growth after HPP treatment [10].…”