Effect of Roll Gap and Mill Speed on the Quality of Oat Flakes

摘要

Oat flakes have various end-uses, for which the quality requirements may be different. Flake size and thickness, color, friability and bulk density are among the most important physical properties. Water absorption and pasting characteristics also are important in some applications. The flakes should be stabilized, that is heat-treated to inactivate lipase. Bulk density of the flakes is often used to control flake thickness, and is also important for ensuring correct pack weights. This study describes the relationship between the bulk density, thickness, color and water absorption of oat flakes. Oat flakes were prepared from Finnish oats by a commercial mill at two speed settings. Five flake thickness levels were obtained by adjusting the gap between the rolls. According to usual practice, flake bulk density was used as an indicator of thickness. Moisture content, flake thickness, and water absorption were determined. Flake thickness correlated with bulk density at the same mill speed. There was also a strong negative correlation between bulk density and water absorption (r=-0.98), which was did not depend on mill speed. The correlation with flake thickness and water absorption was weaker. Moisture content was also related to flake thickness, with thick flakes having higher moisture content. Flakes with a comparable bulk density were generally thinner and whiter at the higher rate of mill throughput. This study showed that bulk density and mill throughput can be used to control the quality of oat flakes. This is a first step towards relating processing conditions of oat flakes to quality parameters.