High-intensity pulsed electric fields processing parameters affecting polyphenoloxidase activity of strawberry juice

Area of Science:

• Food Science and Technology
• Biotechnology
• Biophysics

Background:

• Polyphenoloxidase (PPO) causes undesirable browning and quality degradation in fruit juices.
• Enzyme inactivation is crucial for extending shelf-life and maintaining the quality of strawberry juice.
• Conventional methods may affect juice quality; alternative inactivation technologies are being explored.

Purpose of the Study:

• To investigate the feasibility of using high-intensity pulsed electric fields (HIPEF) for strawberry juice PPO inactivation.
• To optimize HIPEF parameters for maximum PPO inactivation.
• To determine the effectiveness of different HIPEF modes (monopolar vs. bipolar) and treatment conditions.

Main Methods:

• Response surface methodology was employed to analyze the effects of HIPEF parameters.
• Controlled variables included total treatment time (1000–2000 μs), pulse frequency (50–250 Hz), pulse width (1.0–7.0 μs), and polarity (monopolar/bipolar).
• A constant electric field strength of 35 kV/cm was maintained throughout the experiments.

Main Results:

• HIPEF significantly reduced PPO activity in strawberry juice across the tested conditions.
• Bipolar HIPEF treatments were more effective in inactivating PPO compared to monopolar treatments.
• Extended treatment durations further reduced enzyme activity; minimal residual PPO activity (2.5%) was achieved under optimized bipolar conditions (frequency > 229 Hz, pulse width 3.23–4.23 μs, time 2000 μs).

Conclusions:

• HIPEF is a feasible and effective technology for inactivating PPO in strawberry juice.
• Optimized bipolar HIPEF parameters allow for substantial reduction of PPO activity, preserving juice quality.
• This study provides a basis for applying HIPEF in the food industry for enzymatic quality control.