Yield of Stirred Cold Maceration and Extraction of Milled European Black Alder Wood and Bark using Different Solvents

Wood extractives, especially polyphenols, have great influence on the xylem colour of many wood species, which affects the success of hydrothermal wood processing, such as wood drying. One such wood species is European black alder (Alnus glutinosa (L.) Gaertn.), which is prone to forming intense and uneven reddish-orange or reddish-brown discolourations immediately upon harvesting and processing. However, there is lack of published scientific data on the wood and bark extractives of black alder, as well as the most suitable solvents to extract them. In this work, total soluble extractives, phenols, and flavonoids have been quantified in the wood and bark of black alder. Furthermore, the influence of four different polar organic solvents and deionized water on extractives removal yields has been measured. It was found that the bark has much higher levels of extractives as compared to the wood. Furthermore, it has been found that the highest extractive yields were obtained by using methanol as the extraction solvent for all observed compound group classifications.