METHOD OF PRODUCING NATURAL COLOURING AGENT FROM LARCH BARK Russian patent published in 2016 - IPC C09B61/00 

FIELD: chemistry.

SUBSTANCE: invention relates to methods of producing natural colouring agents from natural raw materials and can be used in food, as well as in perfume and textile industry. Larch bark is used as raw material (usually Gmelin larch). Method involves grinding larch bark and water purification, followed by primary extraction in melted water at temperature of 18±2 °C for 12±2 hours and secondary extraction without use of chemical additives at 80±10 °C for 45-60 min, and ratio of water to bark by weight of 1:10 to 1:8. Further, method includes hot filtration of extract and drying to a dry residue at temperature of 15±2 °C to 70±2 °C for 22-24 hours depending on required colour gamma of obtained dye. Evaporated dry residue is crushed to a powder and packaged in said form. Furthermore, after cooling, extract may be stored in liquid form in a closed opaque container.

EFFECT: according to disclosed solution at minimum power consumption ecologically clean and stable dye is obtained, wherein without using additional chemical reagents and with preservation of biologically active substances, and used bark can be used for fertiliser or mulching of depleted soils, which contributes to cleaner technological process.

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