Evaluation of laser diffraction as a fast method for particle size distribution measurement of plant cell structures in whole oat and soy beverages

In food engineering in general and in liquid food processing specifically, accurate measurement of particle size is important, both for product development and daily quality control. Laser diffraction is the dominating method for particle size measurement of e.g., plant cell structures in food and beverage processing. However, the accuracy of the method can be questioned since these particles differ substantially from the isotropic spheres assumed in laser diffraction algorithms. This paper validates laser diffraction for particle size measurement of plant cell structures in whole plant-based beverages, using direct static image analysis. Premixes of oat and soy beverages were prepared and homogenized under different conditions. This was performed with the purpose of creating several beverages with varying particle sizes. The final beverages were either analyzed as prepared or sieved to isolate the plant cell structures. It is concluded that after isolation of the particles of interest, laser diffraction can accurately capture the size of the largest particles (D_v99). These particles are known to be of critical importance for sensory properties and physical stability. For other characteristic particle sizes-such as the D_v90 and D_4,3-laser diffraction and static image analysis correlate but with a lower coefficient of determination.