Development of Maillard reaction related characteristics during malt roasting

Roasting trials with a modified coffee roaster revealed that the attained end-temperature is the key parameter for control of nonenzymatic browning during malt production. The development of the main Maillard reaction related malt characteristics (colour, antioxidative activity and flavour) was therefore assessed under mild, intermediate and intensive roasting conditions with end-temperatures of 120, 150 and 180 degrees C, respectively. Since maximal browning occurred between 125 and 160 degrees C, the rate of colour formation during mild roasting significantly differed from the other two conditions (3.5 versus 15 European Brewery Convention (EBC) units/min). High molecular weight (HMW) melanoidins (> 70 kDa) were mainly generated by intensive roasting (between 157 and 166 degrees C). The sudden formation of HMW melanoidins coincided with the abrupt decrease of the level of vicinal diketones and radical scavenging antioxidants, indicating a possible role for these compounds in the polymerisation reactions that lead to the formation of HMW melanoidins.