Integrated process for the production of natural extracts from black spruce bark

Black spruce bark is an underestimated by-product from Quebec wood industry containing important quantities of valuable chemicals. We are presenting here an integrated process leading to a simultaneous extraction of an essential oil, a hydrosol and a polyphenol enriched hot water extract while the residual bark remains available for heat generation due to its preserved calorific value. Two types of hydrodistillation were tested: steam distillation (SD) and water distillation (WD). Since no difference was found between the two processes neither in respect to the essential oil and hydrosol production nor in respect to their chemical compositions, the focus of the present research was on the hot water extracts obtained from the two processes. The drained extract from water distillation process (WD-DE) was obtained at high yield (21.6%), and was determined to have the phenol and proanthocyanidin contents (337 mg GAE/g, 139 mg CChE/g) in the same range as the control (extract from simple hot water extraction), along with the remarkable concentration of trans-resveratrol (627 mg/100 g dry extract). The results of DPPH radical and ORAC tests indicate that all studied extracts have antioxidant activities, especially the WD-DE. Higher heating values of the remaining bark after extractions were determined to be almost identical as those of the original bark (around 20 MJ/kg), indicating that black spruce bark would still be available for combustion, otherwise its conventional use, after the extraction. The integrated process of black spruce bark extraction presented here represents a new approach to the complete valorization of residual bark from wood transformation.