Arabinogalactan extraction – Biorefining is a process of deep complex chemical refining of timber, aimed at turning its main components into market products with high added value (both large-tonnage and low-tonnage). This includes refining of larch sawdust, as well.
There are various methods of AG extraction from ground larch timber. Due to excellent water solubility of Arabinogalactan, virtually all its extraction methods are based on water extraction of raw material. Extraction temperature in different methods may vary from 23 to 100 C.
The simplest methods include water extraction of larch sawdust at room or higher temperature, followed by extract separation and evaporation. AG sediments with the help of acetone with sodium chloride or ethanol. More complex and multistage methods allow getting AG of high purity degree with simultaneous extraction of biologically active taxifolin. In particular, there is a method of high-purity Arabinogalactan acquisition which starts with water extraction of larchwood pretreated with ethyl acetate and dried. After that the extract is concentrated, mixed with coagulating and flocculating agents, separated from residue and sedimented.
The main disadvantage of the above methods is low AG amount when extraction process is short, as a result of diffusion limitations.
There are various methods of external diffusion intensification in solutions. The simplest is acceleration of reaction feed mixing rate. In order to intensify refinery processes of plant raw material mechanical and mechanochemical activations are successfully used. Mechanical activation boosts the amount of extracted raw material without changing its chemical composition. It sufficiently widens raw material contact surface with the solvent and diffusion limitation of extraction process decreases. Mechanochemical activation methods not only break cell walls but also change chemical composition of plant raw material due to breaking of the weakest chemical bonds and chemical reaction between new active particles.
Among the most effective methods of plant polymer activation mechanoactivation in mills of different designs and treatment with superheated water vapor in non-isobaric conditions can be named. There is also a wide range of methods of AG extracts purification and concentration, with the help of which solutions, allowing us to get high purity degree product, can be obtained. For such solutions a method of spray drying can be applied, which allows to skip the stage of AG redeposition from organic solvent. In order to use Arabinogalactan in food and pharmaceutical industries it is necessary to get purified strong solutions or dry product of high purity degree.