Behaviour of Extractives in Norway Spruce (Picea abies) Bark during Pile Storage

Abstract

The current practices regarding the procurement chain of forest industry sidestreams, such as conifer bark, do not always lead to optimal conditions for preserving individual chemical compounds. This study investigates the standard way of storing bark in large piles in an open area. We mainly focus on the degradation of the most essential hydrophilic and hydrophobic extractives and carbohydrates. First, two large 450 m3 piles of bark from Norway spruce (Picea abies) were formed, one of which was covered with snow. The degradation of the bark extractives was monitored for 24 weeks. Samples were taken from the middle, side and top of the pile. Each sample was extracted at 120 °C with both n-hexane and water, and the extracts produced were then analysed chromatographically using gas chromatography with flame ionisation or mass selective detection and high-performance liquid chromatography. The carbohydrates were next analysed using acidic hydrolysis and acidic methanolysis, followed by chromatographic separation of the monosaccharides formed and their derivatives. The results showed that the most intensive degradation occurred during the first 4 weeks of storage. The levels of hydrophilic extractives were also found to decrease drastically (69% in normal pile and 73% in snow-covered pile) during storage, whereas the decrease in hydrophobic extractives was relatively stable (15% in normal pile and 8% in snow-covered pile). The top of the piles exhibited the most significant decrease in the total level of extractives (73% in normal and snow-covered pile), whereas the bark in the middle of the pile retained the highest amount of extractives (decreased by 51% in normal pile and 47% in snow-covered pile) after 24-week storage.

Valorizing Assorted Logging Residues: Response Surface Methodology in the Extraction Optimization of a Green Norway Spruce Needle-Rich Fraction To Obtain Valuable Bioactive Compounds

“…Condensed tannins (Figure 5) in spruce logging residues were mixtures of procyanidins and prodelphinidins, consistent with previous studies on spruce bark and needles. [48][49][50]78 The yield of condensed tannins was dependent on the extraction time and temperature. Interestingly, there were high-yield ridges at the 90−100 °C temperature range in water and aq.…”

“…48 Logging residues also need to be collected and refined as fresh as possible to avoid the losses of extractives. 49,50 Thus, in this study, the process was kept industrially feasible and rapid while avoiding energy-inefficient drying. Optimization of extraction time and temperature was performed against multiple responses, such as the extract bioactivities, which were detected using antioxidant and antibacterial analyses, and tannin quantification with chromatographic methods.…”

The Sustainable Development of Forest Food

“…Through a literature review and experts' interviews, technological innovation has promoted the development of the forest industry [84][85][86][87]. There are increasing enterprises in the production, processing (transportation), and sales stages of Chinese FFVC.…”