Joseph Lech

Formation of Pyrazines from the Maillard Reaction of Glucose and Lysine-.alpha.-amine-15N

The contribution of amino and amide nitrogen atoms to pyrazine formation in both dry and aqueous systems was investigated. The 15N isotope labeled at the amide side chain of glutamine was chosen to react with glucose at 180 degrees C in the studies. Pyrazine, methylpyrazine, ethylpyrazine, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, 2,3-dimethylpyrazine, vinylpyrazine, and 2-ethyl-5-methylpyrazine were identified from heating the isotope-labeled glutamine with glucose in a dry system. Similar types of pyrazines were also found in an aqueous system. The exception was 2-vinyl-5-methylpyrazine, which was produced instead of 2-ethyl-5-methylpyrazine. These results demonstrated that deamidation did participate in pyrazine production and more than half of the nitrogen sources of pyrazines came from the amide side chains of glutamine. The yields of pyrazines from the dry system were higher than that from the aqueous system.

The floral odour of Peltandra virginica contains novel trimethyl-2,5-dioxabicyclo[3.2.1]nonanes

Abstract The qualitative and quantitative composition of the floral odour of Peltandra virginica was determined by trapping odour components from freshly cut inflorescences on Tenax and Carbotrap adsorbents using a purge and trap apparatus. Analysis showed that a single novel compound, 1,3,6-trimethyl-2,5-dioxabicyclo[3.2.1.]nonane, comprised nearly 70% of the odour. Four isomers of this compound were found in much smaller amounts (1.0–7.6%) while an analogue with m, 142 comprised 13% of the odour. Small amounts (ca 0.3-2.5%) of two isomers of methylundecene and three isomers of dimethyldodecenone were also detected. This is the first case of trimethyldioxabicyclo[3.2.1]nonanes reported in floral odours.