The effect of thermal drying on the contents of condensed tannins and stilbenes in Norway spruce (Picea abies [L.] Karst.) sawmill bark

Norway spruce (Picea abies (L.) Karst.) bark contains marked amounts of polyphenolic compounds. Condensed tannins (CTs) and stilbenes show commercial potential as antioxidants, antimicrobials, preservatives in food cosmetic applications, technochemical products, pharmaceuticals. Storing before the conversion process leads to substantial losses extractives In present study, thermal drying for maintaining content was assessed based on an experiment which samples were dried convection kilns at 40, 50, 60, 70 °C temperatures. The development CTs stilbene contents CT degradation followed 28–34 h. analysed from with thiolysis. Quantities glycosides aglycones water-acetone extracts applying gas chromatography flame-ionization detection (GC-FID). Multilevel regression analysis used analyse statistical differences moisture composition between schemes. initial 35–36 mg g?1 dry material declined 25–31 g-1 average degree polymerisation (DP) decreased slightly, relative proportion prodelphinidins increased significantly 60 A-type linkages slightly increase temperature. mean varied 19 22 mass. Isorhapontin major constituent, a 45–49 % total stilbenes. Stilbene up detected during processes. 10 h, example, 36–43 lost. Degradation activities by enzymes released oxidative reactions after crushing debarking phase concluded be primary mode degradation. results indicate that can preserved moderate temperature not exceeding 50 °C, but may affect their suitability various applications. Sufficient industrial processes is unlikely maintainable through drying. permanence post-drying should practical-scale storage using varying contents.