Pyroglutamic acid development during grape must cooking

A study of the pyroglutamic acid development during must cooking as glutamine and glutamic acid degradation product was carried out. Pyroglutamic acid was detected in two white musts (Trebbiano toscano and Spergola) and in a red one (Lambrusco) previously cooked by means of a laboratory-scale equipment emulating the real process. Results showed that pyroglutamic acid sharply increased and glutamine quickly disappeared during the first stages of the cooking process, while glutamic acid was almost linearly reduced throughout all the process. A study carried out by heating the model solutions of the single amino acids showed that both of them underwent degradation following the same trend observed in the musts.