Characterization of the Maillard reaction in bread crisps

Maillard reaction (MR) is one of the main chemical event occurring during baking. To study the reaction in bakery products, a dry model system is more useful than an aqueous one. In this work, the effects of formulation and processing conditions in a crisp bread system were investigated to test the effects of different additives on both the overall reaction and the formation of MR products such as 5-hydroxymethyl-2-furaldehyde (HMF) and acrylamide. Cylindrical dough made up of flour, water and yeast was baked at 180 degrees C for 35 min and the slices were toasted at different times/temperatures combinations. Browning and water content were monitored along with the kinetic of formation of chemical indicators such as HMF and acrylamide also calculating rate constants and activation energy. These parameters were also monitored in systems added with glycine and asparaginase. During toasting water content follows an exponential trend, being the rate of water loss faster in the initial stage of toasting and at higher temperature. Browning was more intense when toasting at higher temperature and a linear correlations between browning (Delta L*, Delta E*), HMF and acrylamide concentration were observed when toasting at 180 degrees C. HMF and acrylamide content increased with the toasting time and temperature. Their concentrations were strongly dependent on the water content of the final product, and both the addition of glycine and asparaginase are effective in reducing acrylamide content. The addition of glycine enhanced the browning of toasted bread, and slightly increased HMF content at any toasting temperature. The system characterized in this work represents a suitable tool to study the development of the MR in dry systems.