Black oat, rye, and wheat cereals: kinetics and changes during hydrothermal processing

Abstract

The grain hydration process is fundamental in cereal processing but can modify their physical and chemical properties. However, there is a gap in understanding the principles of mass transport (water) and its changes during the hydration phases, especially in rye, which has yet to be studied. A kinetic study was carried out to investigate moisture transfer and changes in starch during oats, rye, and wheat hydration. During the process it was observed that the mass transfer was directly affected by the system's temperature, which indicates changes in the absorption capacity over time. The tracer pigment indicated that water entered the grains by diffusion through the grain coating and capillarity through the fissures. Thermal analyses revealed that the starch remained unchanged at hydration temperatures below 50°C. Mathematical models describe the moisture gain in the different conditions studied, while the generalized model allows the experimental moisture to be predicted. This study contributes to understanding the time/temperature relationship in cereal hydration by presenting a kinetic model and examining changes in starch. This provides valuable insights to optimize the industrial operation of this stage and guides new project development.