Impact of pulsed electric fields on polyphenols extraction from Norway spruce bark

• A new technology for polyphenols recovery from bark pieces is proposed.
• PEF treatment enhances the extraction of polyphenols from Norway spruce bark.
• Efficiency of PEF-treatment is not affected by the initial humidity of the sample.
• PEF treatment does not modify the wood composition (cellulose, hemicelluloses and lignin).

sThe objective of this study is to improve aqueous solid/liquid extraction of the polyphenols contained in Norway spruce (Picea abies   (L.) Karst.) bark by the use of pulsed electric field (PEF) treatment. The feasibility of PEF treatment was studied through two different PEF protocols with an intensity of E=20kV/cmE=20kV/cm. These two PEF protocols are applied at different initial humidity of the bark samples (14% and 21%). PEF treatments protocols were compared to untreated samples (simple diffusion without PEF) and to a diffusion from sawdust of Norway spruce bark. The main parameters for the follow-up of the diffusion kinetics and characterization of extracts were studied: moisture content, pH, electrical conductivity, polyphenols concentration and antioxidant activity. The results of this study showed the positive effect of the pulsed electric fields on intracellular compounds extraction. The PEF treatment enhanced extraction of total phenolic content and antioxidant activity. Indeed, the total phenols content has increased of more than 8 times with the use of PEF treatment. The kinetics of pH and electrical conductivity during treatment were studied. The solid fraction was analyzed and the results showed that PEF treatment does not affect the structure of wood and that there are no modifications of the chemical functions by exposing the samples to PEF treatment.