Preparation, characterization, and thermal pyrolysis of three Maillard intermediates

Maillard intermediates, such as Amadori and Heyns compounds, play a pivotal role in the formation of flavor or adverse Maillard products and thus direct affect the sensory and organoleptic properties of foodstuffs. In this study, three Maillard intermediates, namely N-(1-Deoxy-D-fructos-1-yl)-L-phenylalanine (Fru-Phe), N-(1-Deoxy-maltos-1-yl)-L-phenylalanine (Mal-Phe), and N-(2-Deoxy-D-glucos-2-yl)-L-phenylalanine (Glu-Phe), were chemically synthesized, and their potentials as flavor precursors were evaluated through thermogravimetry (TG), derivative thermogravimetry (DTG), and pyrolysis–gas chromatography–mass spectrometry. TG-DTG analyses indicated that Fru-Phe, Mal-Phe and Glu-Phe were stable at room temperature, with the largest mass-loss rates occurring at 138°C, 141°C, and 127 ℃, respectively. Upon thermal pyrolysis, the major flavor substances observed were 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (DDMP), phenylacetaldehyde, furaneol, and 5-methylfurfuryl alcohol for Fru-Phe; phenylacetaldehyde, maltol, DDMP, isomaltol and 2-acetylfuran for Mal-Phe; and DDMP, furaneol, phenylacetaldehyde, and 2,5-dimethyl pyrazine for Glu-Phe. The principal component analysis (PCA) revealed that the number of saccharide units conjugated to phenylalanine exerted significant effects on the variety and abundance of pyrolysis products at 300°C, while specific attachment positions of sugars became the primary factor directing pyrolysis pathways at 600°C and 900°C. Overall, this study provides a method to regulate the species and amounts of degraded flavor products.