Beef Extract (Extractum Carnis)
Beef extract as produced by Liebig’s method consists of the water-soluble fraction of lean beef: mineral salts, small organic molecules including creatine, creatinine, inosine monophosphate, glutamate and other amino acids, and various nucleotides and peptides. The large structural proteins (myosin, actin) and fats remain in the solid residue and are not present in the extract. The product is dark brown, intensely savoury (the glutamate and nucleotide content drives its umami flavour), and dissolves readily in hot water.
Liebig claimed this fraction captured the vital nutritive essence of meat. Later analytical and physiological work showed it did not: the protein content is negligible, the fat content is negligible, and the nitrogenous substances it contains (creatine, creatinine) are waste-product molecules without caloric value in the human diet. The extract’s flavour and mild stimulant effect on gastric secretion were real; its claimed equivalence to the full nutritive value of the original meat was not.