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Effect of Ohmic Heating on the Extraction Yield, Polyphenol Content and Antioxidant Activity of Olive Mill Leaves

Author

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  • Fereshteh Safarzadeh Markhali

    (CEB–Centre of Biological Engineering, Campus of Gualtar, University of Minho, 4710-057 Braga, Portugal
    LABBELS–Associate Laboratory, 4710-057 Braga, Portugal)

  • José A. Teixeira

    (CEB–Centre of Biological Engineering, Campus of Gualtar, University of Minho, 4710-057 Braga, Portugal
    LABBELS–Associate Laboratory, 4710-057 Braga, Portugal)

  • Cristina M. R. Rocha

    (CEB–Centre of Biological Engineering, Campus of Gualtar, University of Minho, 4710-057 Braga, Portugal
    LABBELS–Associate Laboratory, 4710-057 Braga, Portugal)

Abstract

This study examined the influence of ohmic heating ( OH ), compared to the conventional heating ( Conven ) and Control (solvent) methods, on the extraction of olive mill leaves. The main extraction parameters were: (i) solvent ratio (aqueous ethanol; 40%, 60%, and 80%, v / v ), and (ii) extraction temperature; 45 °C, 55 °C, and 75 °C (for OH and Conven ), and room temperature (for Control ). The selected response variables were extraction yield (%), total phenolic content (TPC), and antioxidant activity (ABTS and DPPH). The ohmic system, compared to Conven and Control , exhibited the greatest effects ( p < 0.001) on increasing (i) extraction yield (34.53%) at 75 °C with 80% ethanol, (ii) TPC at 55 °C (42.53, 34.35, 31.63 mg GAE/g extract, with 60%, 40%, and 80% ethanol, respectively), and (iii) antioxidant potency at 75 °C detected by DPPH and ABTS, in the range of 1.21–1.04 mM TE/g, and 0.62–0.48 mM TE/g extract, respectively. Further, there were relatively similar trends in TPC and antioxidant activity (both methods), regardless of solvent ratios, p < 0.001. These findings demonstrate the potential of ohmic heating, as a green processing tool, for efficient extraction (15 min) of olive leaves. To date, no literature has described ohmic application for olive leave extraction.

Suggested Citation

  • Fereshteh Safarzadeh Markhali & José A. Teixeira & Cristina M. R. Rocha, 2022. "Effect of Ohmic Heating on the Extraction Yield, Polyphenol Content and Antioxidant Activity of Olive Mill Leaves," Clean Technol., MDPI, vol. 4(2), pages 1-17, June.
    • Handle: RePEc:gam:jcltec:v:4:y:2022:i:2:p:31-528:d:830026
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