Formation of Maillard reaction products in bread crust-like model system made of different whole cereal flours

Free and protein-bound Maillard reaction products (acrylamide, 5-hydroxymethylfurfural, alpha-dicarbonyl compounds, N-epsilon-fructosyllysine, N-epsilon-carboxymethyllysine and N-epsilon-carboxyethyllysine) and the reaction precursors (sugars and amino acids) were investigated in bread crust-like systems prepared with different cereal flours. Selected cereals were; whole and refined wheat, whole einkorn, whole rye, whole oat and whole corn. For all cereals, the concentrations of reducing sugars, free amino acids and protein-bound lysine increased significantly after dough fermentation (p < 0.05). Heating the bread crust-like model systems at 200 degrees C for different time periods (5, 15, 30 min) caused significant decrease in the concentration of sugars and amino acids (p < 0.05). Among alpha-dicarbonyl compounds, 3-deoxyglucosone and methylglyoxal were found in high amounts. However, extended heating time caused significant reduction in their concentrations (p < 0.05). Compared to 5 min of heating, higher amounts of 5-hydroxymethylfurfural formation were observed in samples heated for 15 and 30 min. However, prolonging the heating time resulted in a reduction in the amount of acrylamide formed in bread crust-like samples prepared with einkorn and oats. Heating for 5 min caused formation of early and advanced glycation products in bread crust-like samples prepared from all cereals. The amounts of early and advanced glycation products in the high molecular weight fractions of bread crust-like systems were significantly higher than those in bread-crust-like systems, but they decreased rapidly in samples heated for longer time (p < 0.05).