Long-term storage of oat (Avena sativa) flour – an investigation of hydrolytic and oxidative rancidification

Oats (Avena sativa) are commonly kilned to inactivate native lipases, yet the impact of kilning on the storability of oats is not fully understood. In this study the impact of kilning on five different oat varieties during 12 months of continuous storage was investigated. The study included three commercial oat varieties with different lipid contents, and two novel oat lines selected for decreased lipase activity. We show that over the storage time studied, the free fatty acid (FFA) content increased to 80% of total lipid content for non-kilned oats independent of the initial lipase activity. Initial lipase activity did not correlate with FFA formation or lipid oxidation in the non-kilned material, indicating that significantly lower lipase activities than in the studied lines is needed to allow minimization of the heat inactivation. Remarkedly, it was found that the pattern of formation of hydroxylated fatty acids was significantly impacted by kilning.