Effect of a HPP pretreatment on thermal inactivation kinetics of polyphenoloxidase obtained from three apple cultivars

Maria F. Machado, Alexandra Sousa, Sónia M. Castro, Sílvia A. Moreira, Jorge A. Saraiva*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


Enzymatic browning due to the action of polyphenoloxidase (PPO) is highly undesirable and efficient methodologies to avoid/reduce it are of great interest for food industry. The effect of a pressure pretreatment (100 MPa, 15 min, room temperature) on the activity of PPO extracts obtained from three apple cultivars (Bravo de Esmolfe [BE], Reineta [RN], and Golden delicious [GD]), and subsequent thermal inactivation kinetics was evaluated, as a way to more efficiently achieve thermal inactivation of PPO. The effect of pH on PPO activity was also assessed to define the value at which carry out the thermal inactivation of PPO. The enzymatic activity decreased in the order BE, RN, and GD. Two log-linear ranges ([62.5–72.5] °C and [72.5–80.0] °C) of D-value with temperature were found. The pressure pretreatment caused enhanced stability within the range of 62.5–67.5 °C, caused no changes at 70.0–72.5 °C, and decreased the stability at 75.0–80.0 °C (e.g., at 75 °C the D-values for BE, GD, and RN ranged, respectively, from 25.6/27.3, 14.5/18.6, and 8.8/10.4, after/before the pressure pretreatment) and increased thermal sensitivity (decreased the z-value), particularly in the lower temperature range studied (up to 72.5 °C). Practical applications: Knowledge of PPO activity level and its thermal resistance for different cultivars is of interest to develop efficient and optimized enzymatic browning control by thermal treatments. Sequential combination of low intensity pressure treatments followed by thermal treatments can be an interesting approach to enhance enzyme inactivation. In this work was found that after a low intensity pressure pretreatment (100 MPa, 15 min), apple PPO temperature stability could be reduced, since a lower stability (lower D-values) and increased sensitivity toward temperature (lower z-value) was systematically found for PPO thermally inactivated at T > 72.5 °C. These findings are of interest for a more efficient PPO inactivation for enhanced browning control.

Original languageEnglish
Article numbere12570
JournalJournal of Food Process Engineering
Issue number6
Publication statusPublished - Dec 2017


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