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A method for preparing Maillard products under basic conditions was developed. The Maillard reaction products from 4 sugars and 20 amino acids were analyzed with GC/MS. Nitrogen-, oxygen-, sulfur-containing heterocyclic compounds, aromatic compounds and ketene(enal)compounds were selected as key aroma components, and the types and contents were determined. The results showed that: 1) Among the key aroma components, nitrogen-containing heterocyclic compounds were higher in almost all the Maillard reactions. The types and amounts of oxygen-containing heterocyclic compounds were lower, and mainly formed by glucose or fructose. Sulfur-containing heterocyclic compounds were less in the type and content, and formed by cysteine. The types and contents of aromatic compounds and ketene(enal)compounds were less, and formed by some specific amino acids. 2) In the order of the total contents of key aroma components by sugars were: fructose >> xylose > glucose > deoxyribose. 3) The total contents of key aroma components from the different amino acids were different, and the contents from leucine, lysine, phenylalanine and tryptophan were higher. [ABSTRACT FROM AUTHOR]

A convenient one-pot synthesis of fully substituted pyrazoles via three-component condensations of phenylhydrazine, aldehydes, and 1,3-dicarbonyl compounds using ytterbium perfluorooctanoate [Yb(PFO)3] as catalyst under solvent-free conditions is described. The reusable catalyst can be easily prepared and was efficient for the reaction. A possible mechanism is suggested. [ABSTRACT FROM AUTHOR]