Pulsed electric field assisted extraction of phenolic compounds from blueberries

Abstract

Pulsed electric field (PEF) technology can be used to improve mass transfer of inner liquids and intracellular compounds from plant materials [1]. The objective of this study was to investigate the influence of PEF pretreatment of Vaccinium myrtillus L. fruits both on the extraction yield and quality of juice obtained by pressing, and on the subsequent solvent extraction of phenolic compounds from berry press residues (presscake). PEF pretreatment of constant electric field strength (3kV/cm) and varying specific energy (1-10kJ/kg) was applied to blueberries prior to their mechanical pressing. The juice yield, content of phenolic compounds and antioxidant activity of the juice were evaluated and compared to untreated sample (control juice). In addition, berry presscake obtained after juice pressing was subjected to further extraction with acidified aqueous ethanol and the recovery of phenolic compounds from press residues was evaluated. PEF treatments carried out at 3kV/cm and energy input of 1, 5 and 10kJ/kg achieved a cell disintegration index (Zp) of 0.73, 0.77, and 0.80, respectively. PEF pretreatment of blueberries increased the juice yield up to 34% (energy input of 5kJ/kg) as compared to the control. Juice obtained from PEF pretreated berries had also significantly higher content of total phenolics (up to 46%). Furthermore, the total anthocyanins content of juice obtained from PEF pretreated berries was from 34% (energy input 1kJ/kg) to 77% (energy input 10kJ/kg) higher than that of the control juice. In addition, juice of PEF pretreated berries had significantly higher antioxidant activity. Extracts from presscakes obtained after PEF assisted pressing of blueberries had 1.6-fold higher content of total phenolics and 1.7-fold higher content of anthocyanins as compared to the control extract.