A A C C   2 0 0 0   A n n u a l   M e e t i n g

Digital image analysis and laser light diffraction were used to study starch isolated from a variety of wheat classes. A laser light diffraction system provides rapid analysis of large numbers of particles, but is volume-based with results expressed in terms of equivalent spheres. Since larger starch granules in wheat endosperm are oblate spheroids, light diffraction systems introduce errors in size distribution calculations. Size distributions obtained from image analysis can not be directly compared to those of the laser light instrument because image analysis data is number-based while diffraction data is volume-based. Conversion of the number-based image analysis data to a volume-base resulted in similar size distributions as those obtained from diffraction studies. Fewer large type A granules were present in the image analysis data than from diffraction because of perimeter touching edge of field of view effects, but both had similar mean diameters. The type B granules showed the largest differences where many more granules were counted by image analysis than by the diffraction system. Results indicate that laser light diffraction used for routine starch size distribution determinations should be calibrated using image analysis data.