Changes during the extrusion of semolina in mixture with sugars

Wheat semolina and its mixtures with 5% glucose, fructose of sucrose were processed in a sigle screw extruder at the maximum temperature of 140°C and the processing time of 30 s. The nonenzymic browning was only moderate, but it was substantially more intensive in mixtures with glucose or fructose than in the case of wheat semolina or its mixture with sucrose. Red and yellow pigments were mainly formed. The odour acceptability was affected by the presence of sugars almost negligibly, but the intensities were different, higher in extruded mixtures with glucose and fructose than in wheat semolina or its mixture with sucrose. Small differences were observed in the sensory profile. Extrusion of semolina with sugars produced more sensory active volatiles (52-69 identified compounds) than in extruded semolina (41 compounds). Pyrazines, furans and pyrans were the most important sensory active compounds. Their amounts increased by the addition of sugars to semolina; the mixture of semolina with glucose was particularly rich in active compounds. The formation of pyrazines was more enhanced by the addition of fructose than of other sugars. Maltol, butyrolactone and acetic acid were present in large amounts. Even if sensory characteristics were improved by addition of sugars to semolina, the difference was not very pronounced.