Formation of pyrazines from the Maillard reaction of glucose and glutamine-amide-15N

Abstract

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.