Sensory characterisation of the aromas generated in extruded maize and wheat flour

The effects of extrusion temperature, moisture and residence time (RT) on flavour generation in maize and wheat flours processed by direct extrusion cooking have been investigated using quantitative descriptive aroma profiling. Temperature and moisture level were important variables influencing the aroma generation in extrusion of both maize and wheat hour. Changing RT from 35 to 60 s had a relatively small effect on the aroma of extruded maize. A greater effect of RT on aroma generation was noted for extruded wheat flour. The maize and wheat extrudates were described by similar aroma vocabularies, although low-intensity sulphury and musty notes were observed in the extruded wheat. The extrudates from the lowest extrusion temperature (120 degrees C) and higher moisture levels (18 and 22%) were mainly characterised by porridge-like, cooked milk, cooked vegetable terms. At the intermediate conditions (150 degrees C and 18% moisture), popcorn, toasted and puffed wheat notes dominated the extrudates from both cereals, with the popcorn note more characteristic for the extruded maize samples. The popcorn aroma was lower in the extrudates prepared under the most severe conditions (180 degrees C and 14% moisture), where puffed wheat, burnt and toasted aromas were scored at relative high intensity. (C) 1998 Academic Press.