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In this work, optimal Pulsed Electric Fields-assisted extraction conditions were selected in order to intensify the extractability of polyphenol compounds with high antioxidant activity from potato peels.Effectiveness of PEF as cell disintegration technique was confirmed using both impedance measurements and Scanning Electron Microscopy (SEM). Solid-liquid extraction (SLE) for both untreated and PEF pre-treated potato peels was optimized to determine the most effective solvent concentration (0-100% ethanol in water) as well as extraction temperature (20-50°C) and time (30-240 min) using response surface methodology. Total phenolic compounds (TPC) and antioxidant activity (DPPH) of the extracts were determined. Results showed that the application of PEF prior to SLE has the potential to reduce duration, temperature and consumption of solvent to achieve the same recovery yield of phenolic compounds. Under optimized conditions (54% ethanol, 233 min and 50°C for SLE; 52% ethanol, 230 min and 50°C for PEF), the extracts obtained from PEF pre-treated samples showed higher total phenolics yield (10%) and antioxidant activity (9%) as compared to the control extraction. Finally, HPLC-DAD analysis revealed the major classes of the detected polyphenolic compounds as chlorogenic, caffeic, syringic, protocatechuic and p-coumaric acids, and no significant degradation of individual polyphenols due to PEF application was observed.

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The present study aimed to investigate the effect of the main pulsed electric field (PEF) process parameters on the cell damages of A. platensis microalgae and the extractability of valuable compounds [water-soluble proteins (WSP), C-phycocyanin (C-PC), and carbohydrates (CH)]. Aqueous microalgae suspensions (2%, w/w) were PEF-treated at variable field strength (E = 10, 20, 30 kV/cm), total specific energy (W T = 20, 60, 100 kJ/kg susp), and inlet temperature (25, 35, 45 • C), with either monopolar or bipolar square wave pulses (5 µs of width, delay time between pulses of opposite polarities = 1, 5, 10, 20 µs), prior to extraction with water at room temperature (25 • C) for up to 3 h. High-pressure homogenization (HPH) treatment (P = 150 MPa, 3 passes) was used to achieve complete cell disruption to quantify the total extractable content of target intracellular compounds. Scanning electron microscopy (SEM) and optical microscopy analyses clearly showed that PEF merely electroporated the membranes of algae cell, without damaging the cell structure and forming cell debris. The application of PEF treatment (monopolar pulses, 20 kV/cm and 100 kJ/kg susp) at room temperature significantly enhanced the extraction yield of WSP [17.4% dry weight (DW)], CH (10.1% DW), and C-PC (2.1% DW), in comparison with the untreated samples. Bipolar pulses appeared less effective than monopolar pulses and led to extraction yields dependent on the delay time. Additionally, regardless of pulse polarity, a clear synergistic effect of the combined PEF (20 kV/cm and 100 kJ/kg susp)-temperature (35 • C) treatment was detected, which enabled the extraction of up to 37.4% (w/w) of total WSP, 73.8% of total CH, and 73.7% of total C-PC. Remarkably, the PEF treatment enabled to obtain C-phycocyanin extract with higher purity than that obtained using HPH treatment. The results obtained in this work suggest that the application of PEF combined with mild heating could represent a suitable approach for the efficient recovery of water-soluble compounds microalgal biomass.

The objective of this study was to evaluate the potential of green solvents for extractions of bioactive compounds (BACs) and essential oils from wild thyme (Thymus serpyllum L.) using theoretical and experimental procedures. Theoretical prediction was assessed by Hansen solubility parameters (HSPs) and conductor-like screening model for realistic solvents (COSMO-RS), to predict the most suitable solvents for extraction of BACs. An experimental procedure was performed by nonthermal technology high voltage electrical discharge (HVED) and it was compared with modified conventional extraction (CE). Obtained extracts were analyzed for chemical and physical changes during the treatment. Theoretical results for solution of BACs in ethanol and water, as green solvents, were confirmed by experimental results, while more accurate data was given by COSMO-RS assessment than HSPs. Results confirmed high potential of HVED for extraction of BACs and volatile compounds from wild thyme, in average, 2.03 times higher yield of extraction in terms of total phenolic content was found compared to CE. The main phenolic compound found in wild thyme extracts was rosmarinic acid, while the predominant volatile compound was carvacrol. Obtained extracts are considered safe and high-quality source reach in BACs that could be further used in functional food production.

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