2, 5-Diketopiperazines (Cyclic Dipeptides) in Beef: Identification, Synthesis, and Sensory Evaluation

ABSTRACT:  Stewed beef and grilled dry aged beef were analyzed as part of an in-depth analytical program, with the aim of creating new flavors incorporating only compounds identified in the target foods and identifying new synthesis targets. In-house GC-MS analyses of several types of cooked beef have identified over 1000 volatile and semivolatile components; many for the 1st time. Among the semivolatiles detected were ten 2, 5-diketopiperazines (cyclic dipeptides) previously unreported in beef. These cyclic dipeptides are cis -cyclo( l -Ile- l -Pro), cis -cyclo( l -Leu- l -Pro), cis -cyclo( l -Pro- l -Pro), cis -cyclo( l -Pro- l -Val), cis -cyclo( l -Ala- l -Pro), cyclo(Gly- l -Pro), cyclo(Gly- l -Leu), cis -cyclo( l -Met- l -Pro), cis -cyclo( l -Phe- l -Pro), and cis- cyclo( l -Phe- l -Val). All 10 cyclic dipeptides were synthesized and evaluated organoleptically. Among them cis -cyclo( l -Leu- l -Pro), cis -cyclo( l -Met- l -Pro), and cis -cyclo( l -Phe- l -Pro) were found to be of particular organoleptic interest.