Table 3.
Summary of extraction of bioactive compounds obtained from tea under various PEF conditions
| Sample | Extraction conditions* | b | Keynote (s) | Reference |
|---|---|---|---|---|
| Green tea | 38.4 kV/cm, 20 °C, 160 µs, 667 pps, 2 µs | Polyphenols and free amino acids |
- A promising technology to maintain the quality of the bioactive compounds and color - The inactivation of microorganisms (e.g., Escherichia coli and Staphylococcus aureus) - Synergistic effect in the reduction of the microorganisms by the low-temperature storage and antibacterial property of polyphenols extracted -No significant effect on polyphenol extraction with PEF (1.82 mg/mL (PEF) vs 1.82 mg /ml (untreated)) and 36% in amino acids compared to conventional methods |
Zhao et al. [185] |
| Green tea | 20–40 kV/cm, 121 °C, 50–200 µs, 667 pps, 2 µs | Polyphenols, catechins, and free amino acids | High retention of color and bioactive compounds | Wang et al. [183] |
| Green tea infusions | 38.4 kV/cm, 37 °C, 200 µs, 667 Hz, 2 µs | NR | - Shelf-life period more than 90 days (at 37 °C) for the infusions with PEF | Zhao et al. [34] |
| Green tea infusions | 20 to 40 kV/cm, 5–15 °C, 200 µs, 667 pps, 2 µs | Catechins, polyphenols, and free amino acids |
- Increased content of amino acids (specifically theanine) by 7.5% at 40 kV/cm with the loss of volatiles (≈10%) - Efficient retention of the bioactive compounds and color |
Zhao et al. [35] |
| Tea | 0.9 kV/cm, 5 °C, 5 × 105 µs, 5 × 104 µs | Polyphenols |
- 27% maximum extraction yield for polyphenols - Significant effects of the pulse and strength of electric field on the extraction yield |
Zderic et al. [180] |
| Black tea | 20 kV/cm, 95.83 µs, 125 Hz, 2 µs | Total solids, polyphenols, and amino acids |
- A 22.7% extraction yield for instant black tea powder - Improved the tea solubility in cold water along with reducing the tea cream - Total polyphenols (40.73 mg/g), amino acids (20.79 mg/g) and total solids (221.19 mg/g) were extracted using PEF |
Ye et al. [186] |
| Unfermented Pu’er tea | 18 kV/cm, 60 min (extraction time), 200 pps, 120 Hz, 0.3 µs | Polyphenolics, and theine |
- Improved the taste, aroma and other sensory parameters in tea samples compared with the effect of natural aging on teas - Effective in the artificial aging as it improved the content of tea extract and its taste - Shorter and quicker method for aging of unfermented Pu’er tea - New method to enhance the tea quality and safety - Total polyphenols extraction was ~ 30% and theanine ~ 4% and did not show significant difference compared to conventional method |
Chen et al. [174] |
| Tea | 0.9 kV/cm, 10 °C, 3 × 106 µs | Polyphenols |
- 27% maximum extraction yield for polyphenols -Direct and positive relationship between the time of pulse and the treatment time |
Zderic and Zondervan [33] |
| Tea | 1.1 kV/cm, 100 µs, 0.1 × 10−3 s, 50 pulses | Polyphenols | Maximum extraction yield (32.5%) of polyphenols with the PEF without destroying bioactive compounds compared to the conventional hot-brewing method | Zderic and Zondervan [179] |
*1- Field strength (kV/cm), 2- Temperature (°C), 3- Pulse duration (µs), 4- Pulses per second (pps)/Frequency (Hz), 5- Pulse width (µs), NR not reported