Pyroglutamic acid in wine and fruit juices: Risk and avoidance of unwantedaroma influencing

The content of pyroglutamic acid was determined in 70 different beverages a fter cation exchange: Chromatography. The highest concentration of the 55 a nalyzed wine samples was 0.61 gli. Sensory investigations demonstrated that the detection limit for off-flavours caused by pyroglutamic acid is depend end of the species of the grapes and the age of the wine. The lowest tastab le concentration of pyroglutamic acid in wine was 0.1 g/l. Approximately ha lf of the investigated wines showed Values which were above that concentrat ion. Fresh prepared fruit juices did not contain more than 0.04 g/l pyroglu tamic acid. After intensive thermic treatment the values increased signific antly and reached in one sample 0.92 g/l. A commercially available tomato j uice contained 1.55 g/l pyroglutamic acid, which was the highest concentrat ion of all samples. The amino acid analysis of fresh fruit juices and model solutions showed that pyroglutamate is formed in the presence of glutamic acid or glutamine. After autoclaving latter is converted almost quantitativ ely to pyroglutamate. Depending of the plant species the formation of pyrog lutamic acid can almost be eliminated, if there is no excessive heat treatm ent and if the nitrogen manuring is adapted to the real demand, In case of a necessary thermic treatment, an amino acid analysis is helpful to estimat e the risk of pyroglutamate formation.