Optimization of Pulsed Electric Field as Standalone "Green" Extraction Procedure for the Recovery of High Value-Added Compounds from Fresh Olive Leaves.

Olive leaves (OLL) are reported as a source of valuable antioxidants and as an agricultural by-product/waste. Thus, a twofold objective with multi-level cost and environmental benefits arises for a "green" standalone extraction technology. This study evaluates the OLL waste valorization through maximizing OLL extracts polyphenol concentration utilizing an emerging "green" non-thermal technology, Pulsed Electric Field (PEF). It also provides further insight into the PEF assistance span for static solid-liquid extraction of OLL by choosing and fine-tuning important PEF parameters such as the extraction chamber geometry, electric field strength, pulse duration, pulse period (and frequency), and extraction duration. The produced extracts were evaluated via comparison amongst them and against extracts obtained without the application of PEF. The Folin-Ciocalteu method, high-performance liquid chromatography, and differential scanning calorimetry were used to determine the extraction efficiency. The optimal PEF contribution on the total polyphenols extractability (38% increase with a 117% increase for specific metabolites) was presented for rectangular extraction chamber, 25% v/v ethanol:water solvent, pulse duration (tpulse) 2 µs, electric field strength (E) 0.85 kV cm-1, 100 µs period (Τ), and 15 min extraction duration (textraction), ascertaining a significant dependence of PEF assisting extraction performance to the parameters chosen.

Pulsed Electric Field and Salvia officinalis L. Leaves: A Successful Combination for the Extraction of High Value Added Compounds.

The present study aimed to evaluate the pulsed electric field (PEF)-assisted extraction of phytochemicals from Salvia officinalis L. leaves. The study parameters included a PEF pulse duration of 10 or 100 µs for 30 min, using different "green" extraction solvents: pure ethanol, pure water, and their mixtures at 25, 50, and 75% v/v concentrations. The resulting extracts were evaluated against reference extracts obtained without PEF. For estimation of the extraction efficiency, the content in total polyphenols, individual polyphenols, and volatile compounds, as well as the resistance to oxidation, were determined. The optimal PEF contribution on the total and individual polyphenols, rosmarinic acid, extractability (up to 73.2% and 403.1% increase, respectively) was obtained by 25% v/v aqueous ethanol solvent using a pulse duration of 100 µs. PEF was proven to also affect the final concentration and composition of volatile compounds of the extracts obtained.