Influence of extrusion on storage quality of dried oat noodles: Lipid degradation and off-flavours.

The aim was to investigate whether extrusion could improve the storage stability of dried oat noodles by inhibit lipid-degrading enzyme activity and the degradation of lipids. Thus, noodles were made from extrusion-treated oat under two treatment conditions and subjected to 12-week storage. Extrusion completely inactivated lipase and peroxidase in oat flour, while lipoxygenase activity persisted at a low level. Processing of dried oat noodles also influenced enzyme activity dramatically. For instance, the most significant impact was observed for lipase activity, which dropped to ca. 11 U∙min−1∙g−1 in the freshly prepared noodles made from non-heat-treated oat flour. Lipid hydrolysis was greatly controlled in extrusion-treated noodles as fatty acid values did not increase during storage. The total lipids decreased more in the extrusion-treated groups than in the control sample, which may indicate the promotion of extrusion in non-enzymatic reactions, as the initial values of volatile compounds were much higher. Interestingly, the occurrence of non-enzymatic lipid oxidation should not be severe during storage, as the reduction of tocols and the accumulation of volatile compounds were only moderate in extrusion-treated oat noodles. In conclusion, extrusion could be an effective method for enhancing the storage stability of dried oat noodles. [Display omitted] • Lipase and peroxidase were completely inhibited by extrusion in dried oat noodles. • Lipoxygenase persisted activity at low level after extrusion. • Enzymatic reaction was the main factor to cause lipid-degradation during storage. • Formation of volatile lipid oxidation products was greatly controlled by extrusion. • Extrusion may confer some advantages in the production of stable oat food products. [ABSTRACT FROM AUTHOR]