Kenneth J. Kraut

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-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.

Identification of 2-ethyl-4-methyl-3-thiazoline and 2-isopropyl-4-methyl-3-thiazoline for the first time in nature by the comprehensive analysis of sesame seed oil.

Toasted sesame seed oil was comprehensively analyzed. It was extracted using the SAFE (Solvent-Assisted Flavor Evaporation) technique. The extract was analyzed by GC and GC-MS on 2 phases and a total of 87 components were identified, confirmed, and are presented in this paper. The major components were methylpyrazine; 2,5-dimethylpyrazine; 2,6-dimethylpyrazine; 2-ethyl-3,6-dimethylpyrazine; furfuryl alcohol; and guaiacol. In addition, as part of this analysis, 2-ethyl-4-methyl-3-thiazoline and 2-isopropyl-4-methyl-3-thiazoline were confirmed as being present in a natural product for the first time. Their identification, confirmation, and sensory evaluation have been documented here.