Cereal Chem 46:227 - 241.  |  VIEW ARTICLE
The Microscopic Structure of Popped Cereals.

R. M. Reeve and H. G. Walker, Jr. Copyright 1969 by the American Association of Cereal Chemists, Inc. 

The endosperms of grains expanded by popping show different degrees of starch granule gelatinization. In barley and wheat, which do not expand greatly, some starch granules undergo complete gelatinization without appreciable granule expansion; other gelatinized granules appear to have expanded and fused. Localized cell-wall rupturing occurs when the kernels split open; a few intracellular voids or enlarged bubbles occur in the gelatinized starch as a result of popping explosion. Ungelatinized and partly gelatinized starch granules predominate immediately beneath the aleurone and near the scutellum. Localized cell-wall rupturing also occurs in expanded endosperms of popped grain sorghum or milo, popcorn, and dent corn, but the spongy, expanded endosperms consist of intact cells within which the gelatinized starch forms a characteristic "soap-bubble" structure. Gelatinized granules expand directly to form the individual bubbles. Expansion is much less pronounced in dent corn than in milo and popcorn, in which more cell rupturing occurs to form voids. The soap-bubble structure also is less extensively developed in all poorly popped kernels. Some unaltered and partly gelatinized starch is present immediately beneath the aleurone and near the scutellum, even in fully popped kernels. Differences in distribution of horny and floury endosperm, and differences in their protein content influence the capacity to expand when different cereals are popped. There appear also to be some differences between starch granules. More fundamental information on starch composition in different cereals is needed for a more complete understanding of interrelationship between protein, starch, and structure in relation to popping expansion.