The invention relates to nitroxy group mediator and the reaction medium containing the carbohydrate and / or carbohydrate derivatives and comprising contacting the peroxidase enzyme, carbohydrates and / or carbohydrate derivatives having at least one primary alcohol group a method of oxidation, the initial reaction medium contains at least 10 wt.% of carbohydrates and / or carbohydrate derivative, a peroxidase enzyme oilseed peroxidase and a hydroperoxide and an alkali compound to the reaction medium, is that of pH gradually comprising adding to be maintained between 3.5 to 10.0, relates to the aforementioned method.