Since Papin (XVII th century) gelatine was expected to be substituted for meat in poor peoples' food. Its nutritional value was studied by academic Commissions, from 1803 to 1841. The question has been given up after 1870 when the growth in agricultural yield owing to fertilizer use made food shortage vanish. In this paper, successive extraction methods are examined, and Chevreul's participation in the academic debates (XIX th century) is emphasized.