That is, the decomposition of albuminous matter (i.e. water-soluble proteins) caused sugar to transform to alcohol.[4][5] Liebig held this view until his death in 1873.[4] A different theory was supported by Charles Cagniard de la Tour and cell theorist Theodor Schwann, who claimed that alcoholic fermentation depended on the biological processes carried out by brewer's yeast.[6][5]