Effect of processing parameters on the quality of oat flakes

Abstract

Quality of oat flakes is dependent on end-use. Specific weight is used to steer the flaking process, and is important in ensuring that the correct pack weight is achieved. It is also related to flake thickness. Flake thickness in turn may affect other quality parameters such as water absorption, colour and breakage of the flakes. The aim of this study was to describe the effect of specific weight on the quality parameters of oat flakes. Oat flakes were prepared from locally grown oats by a commercial mill. Five flake thickness levels were obtained by adjusting the gap between the rolls. According to usual practice, specific weight was used as an indicator of thickness. For determination of moisture content and pasting properties, samples were ground using a pin mill and cyclone mill. Thickness was measured from 10 randomly selected flakes. Moisture content was determined by air-drying. Water absorption was determined by weighing 50 g of flakes into a beaker and adding 200 ml of water at 24°C. After 5 min the mixture was spread over a pre-weighed 0.85 mm screen, tilted at 28° from the horizontal and allowed to drain. Flake colour was measured with a tri-stimulus instrument. Flake size distribution was measured using 5 and 2.5 mm round-holed sieves, from a representative sample obtained with a sample divider. Pasting properties were measured using a Rapid Viscoanalyzer. There was a positive correlation between specific weight and flake thickness. Specific weight showed strong negative correlations with water absorption and the peak viscosity of flakes ground in a pin mill, however there were no significant difference between finely ground flakes, which suggests differences in the particle size distribution or extractability of starch. Thin flakes were whiter. The relationship between specific weight and breakage was less clear, although thin flakes were more susceptible to breakage. These results suggest some methods for measuring the quality of oat flakes and show the effect of a milling parameter (specific weight) on these quality parameters.