Effects of glucose and acid-hydrolysed vegetable protein on the volatile components of extruded wheat starch

The volatile components produced in wheat starch, and wheat starch combined with 1% glucose, 1% acid-hydrolysed vegetable protein (aHVP) or 1% glucose and 1% aHVP, extruded under different processing conditions (temperatures of 150 or 180 °C and moisture content of 16% or 20%) were identified by gas chromatography-mass spectrometry (GC-MS). Gas chromatography olfactometry (GCO) was used to assess the odour intensity of volatile components present in the starch and starch/glucose/aHVP extrudates obtained at 180 °C. In total, 70 compounds were identified in the eight extrudates. The smallest number (24) was found in the extrudate of the starch/glucose mixture and the largest number (67) in the extrudate of the starch/glucose/aHVP mixture, both processed at 180 °C. Lipid degradation products, such as alkanals, 2-alkanones, 2-alkenals and 2,4-alkadienals, were present in all extrudates in significant quantities. However, in those extrudates containing aHVP, Strecker aldehydes were quantitatively the dominant components. Maillard reaction products, such as pyrroles and pyrazines, were only found in extrudates containing both glucose and aHVP whereas sulphur-containing aliphatic compounds were found in all extrudates containing aHVP. The production of the Maillard reaction products and sulphur-containing compounds were favoured by extrusion at 180 °C. Sensory analyses showed that each of the eight extrudates had different odours, and that the extrudates containing both glucose and aHVP possessed the highest overall odour intensity.