Background: Normal pressure steaming (NPS), autoclaved steaming (AS), and hot-air roasting (HAR) are widely used to deactivate oat enzyme in the oat-processing industry. Infrared roasting (IR) is a new oat deactivation method, and is welcomed and employed by increasing numbers of oat-processing plants in China. It is widely known that oat starch plays an important role in the processing function of oat food, and that oat beta-glucan and lipid contribute greatly to the health benefits of oat food. However, the effects of steaming and roasting treatments on the starch, beta-glucan and lipid in oat kernels are poorly known.
Results: In this research, the level and distribution of beta-glucan and lipid in oat kernels with and without deactivation treatments were tested. We also measured the viscosity properties of oat flour from kernels after NPS, AS, HAR and IR treatments, and examined the effects of these treatments on oat starch granularity using scanning electron microscopy. The results showed that the deactivation treatments did not have significant effects on oat beta-glucan and lipid levels in oat kernels (P < 0.01). The distribution of beta-glucan and lipid in enzyme-deactivated kernels was very similar to that in normal kernels. NPS, AS, HAR and IR treatments changed the shape of starch granules, crumbled large starch granules, reduced the connection between the protein network and starch granules, and improved starch gelatinization properties.
Conclusions: NPS, AS, HAR and IR treatments can change the structure of oat starch granules and improve the viscosity property of oat starch without causing beta-glucan and lipid loss to oat food.