Volatile components in maize flour, extruded under different conditions obtained by varying product temperature (120, 150, or 180 °C), moisture level (14, 18, or 22%), and residence time (35 or 60 s), were identified and evaluated by gas chromatography/mass spectrometry (GC/MS) and GC olfactometry (GCO). Eighty compounds were identified in the headspace collections of the extrudates. Increasing the product temperature, reducing the moisture level, or prolonging the residence times generally increased the numbers and quantities of Maillard-derived compounds, such as pyrazines, pyrroles, furans, and sulfur-containing heterocycles. In low-temperature (120 °C) and high-moisture (22%) extrusions, the main volatiles were compounds associated with lipid degradation, with few compounds derived from the Maillard reaction. Increasing the temperature and reducing the moisture level to 18% gave rise to the formation of some pyrazines and thiophenones. A marked increase in quantities of 2-furfural, 2-furanmethanol, and alkylpyrazines occurred in the extrusions at 180 °C and 14% moisture level. Under these conditions, other nitrogen- and sulfur-containing heterocyclic compounds were also generated. GCO assessments identified 2-acetyl-1-pyrroline and 2-acetylthiazole as compounds that contributed to cereal-like odors of the extrudates. Some other sulfur-containing compounds were also believed to be involved in the aroma of extrudates processed at 180 °C and 14% moisture level. Keywords: Cereal; maize; extrusion processing; aroma; volatiles; Maillard reaction

Three batches of oats were extruded under four combinations of process temperature (150 or 180 degrees C) and process moisture (14. 5 and 18%). Two of the extrudates were evaluated by a sensory panel, and three were analyzed by GC-MS. Maillard reaction products, such as pyrazines, pyrroles, furans, and sulfur-containing compounds, were found in the most severely processed extrudates (high-temperature, low-moisture). These extrudates were also described by the assessors as having toasted cereal attributes. Lipid degradation products, such as alkanals, 2-alkenals, and 2, 4-alkadienals, were found at much higher levels in the extrudates of the oat flour that had been debranned. It contained lower protein and fiber levels than the others and showed increased lipase activity. Extrudates from these samples also had significantly lower levels of Maillard reaction products that correlated, in the sensory analysis, with terms such as stale oil and oatmeal. Linoleic acid was added to a fourth oat flour to simulate the result of increased lipase activity, and GC-MS analysis showed both an increase in lipid degradation products and a decrease in Maillard reaction products.

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