CHAPTER XXIII - PHOTOMICROGRAPHS OF STARCHES

Abstract

Publisher Summary Different varieties of unmodified starch exhibit wide variations in granule appearance. Sizes and shapes range from the small, angular granules of rice to the large, smooth, oval granules of potato. Ordinary light microscopy, with a resolution of 2000-2500 A can be used to examine the hilum of granules as well as granule shape, size, and size distribution. Observations under the light microscope are sometimes difficult to interpret owing to problems in distinguishing surface and internal structures. The use of a scanning electron microscope (SEM) for examining granule morphology has two major advantages over use of a light microscope. This instrument permits the study of the fine surface structure of starch and cereal products in general. Angular granules show pronounced pressure facets from field drying. The light microscope shows a centric hilum and polarization crosses that are moderate to strong in brightness. SEM also shows the mixture of rounded and angular granules. The more spherical granules have smooth or more regular surfaces compared to those of the angular granules, which are often grooved or dimpled.