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

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-LeuL-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), ciscyclo( 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.