The Presence of Hippuric Acid in Milk

During research on the ether-extractable acidic material from heated milk, an unidentified crystalline substance was recovered. Its physical and chemical properties suggested that it was hippuric acid (benzoyl glycine). Before investigating the matter further, a fairly comprehensive search of the literature was made concerning the possible presence of this compound in milk. One such reference was found. While concentrating the biotin-containing fraction of milk, Karabinos and Dittiner (5) obtained 11 g. of hippuric acid from 1,160 kg. of milk, equivalent to a concentration of approximately 1 mg./100 ml. However, the authors state that the concentration may have been considerably greater since it is not known how much of the compound was lost in the process of isolation. In order to supplement this limited information, studies were undertaken to confirm the presence and determine the concentration of hippuric acid in milk.