Pyroglutamic acid development during grape must cooking.

A study of the pyroglutamic acid developmentduring must cooking as glutamine and glutamic acid degradationproduct was carried out. Pyroglutamic acid wasdetected in two white musts (Trebbiano toscano andSpergola) and in a red one (Lambrusco) previously cookedby means of a laboratory-scale equipment emulating thereal process. Results showed that pyroglutamic acid sharplyincreased and glutamine quickly disappeared during thefirst stages of the cooking process, while glutamic acid wasalmost linearly reduced throughout all the process. A studycarried out by heating the model solutions of the singleamino acids showed that both of them underwent degradationfollowing the same trend observed in the musts