Sensory and instrumental analyses of volatiles generated during the extrusion cooking of oat flours

Three batches of oats were extruded under four combinations of process temp erature (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 b y GC-MS. Maillard reaction products, such as pyrazines, pyrroles, furans, a nd sulfur-containing compounds, were found in the most severely processed e xtrudates (high-temperature, low-moisture). These extrudates were also desc ribed by the assessors as having toasted cereal attributes. Lipid degradati on 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 debr anned. It contained lower protein and fiber levels than the others and show ed increased lipase activity. Extrudates from these samples also had signif icantly lower levels of Maillard reaction products that correlated, in the sensory analysis, with terms such as stale oil and oatmeal. Linoleic acid w as added to a fourth oat flour to simulate the result of increased lipase a ctivity, and GC-MS analysis showed both an increase in lipid degradation pr oducts and a decrease in Maillard reaction products.