Light-colored lignin fragment

The present invention relates to a method for preparing lignin fragments with a lightness (l*) value of more than 65 comprising a plurality of cycles including a first cycle comprising the steps of a. providing a lignocellulose-containing composition, b. heating the composition of step a) together with an aldehyde or an acetal in the presence of an acidic catalyst and optionally a solvent, c. filtering the reaction to obtain a lignin containing filtrate 1 and a cellulose-rich filter cake 1, a second cycle comprising the steps of d. adding an aldehyde or an acetal, an acidic catalyst and optionally a solvent to the cellulose- rich filter cake 1 obtained in step c), e. heating the composition of step d), f. filtering the reaction to obtain a lignin containing filtrate 2 and a cellulose-rich filter cake 2, one or more further cycles involving g. repeating steps d to f) n times to obtain a cellulose-rich filter cake n+2 and a lignin containing filtrate n+2, wherein n is at least 1, and a separation step including the step of h. isolating the lignin-fragments of the lignin containing filtrate n+2.