Method for producing a rosebay willowherb beverage with a high gamma-aminobutyric acid content

A method for producing rosebay willowherb tea having a high gamma-aminobutyric acid (GABA) content, comprising:

• freezing a raw material comprising rosebay willowherb leaves at a temperature of from −45° C. to 0° C. or cooling the raw material to a temperature below a dewpoint;
• next, heating the raw material up to a temperature of 15-25° C.;
• subsequently grinding the raw material to produce a homogeneous plant mass;
• treating the resulting plant mass with an aqueous solution of vitamin B6 in an amount of 0.10-0.25 g of vitamin B6 per 1 kg of the plant mass and with an aqueous suspension of glutamic acid or a solution of a sodium or potassium or magnesium or calcium or ammonium or lithium or zinc salt of glutamic acid in an amount of 6.4-10.6 g of glutamic acid or one of said salts per 1 kg of the plant mass;
• further, fermenting the plant mass at 22-40° C. for 2-10 hours;
• and
• after that, drying the plant mass at 30-55° C. for 6-12 hours to produce a final product, wherein a content of vitamin B6 in the solution added is 0.5%-1%, and a content of glutamic acid in the suspension or a content of the salt of glutamic acid in the solution is 5% or 20-25%, respectively.