Factors affecting sorghum protein digestibility

Protein bodies of seeds: Ultrastructure, biochemistry, biosynthesis and degradation

To understand the influence of the sorghum and maize endosperm protein matrix honeycomb structure on starch hydrolysis in flours, three-dimensional fluorescence microscopy was applied to floury and vitreous endosperm flours cooked under various conditions. Cooking caused the collapse and matting of the sorghum and maize vitreous endosperm matrices, with the effect being greater in sorghum. The effect of cooking was rather different in the floury endosperm in that the protein matrices expanded and broke up to some extent. These effects were a consequence of expansion of the starch granules through water uptake during gelatinization. Cooking in the presence of 2-mercaptoethanol caused an expansion of the vitreous endosperm matrix mesh due to breakage of disulfide bonds in the protein matrix. Mercaptoethanol also caused an increase in the proportion of β-sheet structure relative to α-helical structure of the endosperm proteins. Increased energy of cooking caused collapse of the sorghum matrix. Disul...

Influence of Cooking Conditions on the Protein Matrix of Sorghum and Maize Endosperm Flours

Celiac disease is a serious condition affecting millions of individuals. Those afflicted with this illness are resigned to a lifelong avoidance of products containing the storage prolamin proteins found in cereal grains wheat, rye, and barley. Since many food products are based on these cereals, especially wheat, celiac patients have very limited food choices, and those that are available to them are generally poor in quality, often nutritionally deficient, and expensive. Furthermore, this condition also indirectly affects their families and friends with whom they share meals. Thus, a burgeoning need exists to develop nutritious, palatable, and affordable foods, especially staples like bread and pasta, for these individuals and their families and friends who are accustomed to wheat based products. Grain sorghum and its proteins are safe for celiac patients and individuals with varying levels of gluten intolerances. However, the main sorghum proteins, kafirins, are resistant to digestion. They are also difficult to extract and modify in an industrial-scale process and with food-compatible chemicals, thus limiting their use in foods. This review describes studies on kafirin extraction and methods for modifying sorghum proteins for improved nutrition and functionality, as well as food applications. Armed with this knowledge, scientists and technologists will be in a better position to identify opportunities that will further enhance the nutritional and functional value of sorghum proteins.

Sorghum proteins: the concentration, isolation, modification, and food applications of kafirins.

The Biochemical Basis and Implications of Grain Strength in Sorghum and Maize

The ultrastructure of endosperm protein from 7 habrids and 8 experimental lines was studied with both transmission and scanning electron microscopes. Vitreous endosperm shows a well-developed 2-component structure consisting of protein bodies embedded in a matrix protein. The aqueous alcohol-soluble fraction (prolamine) proved to be the major component of globular protein bodies. The surrounding matrix protein consisted mostly of glutelin. Globular protein bodies have a nuclear that is insoluble in aqueous alcohol. Protein bodies of almost all grain sorghums were 2-3 μm, in diam. One experimental line with above average lysine content had smaller protein bodies, a condition which verifies the negative correlation between prolamine and lysine. Distribution of protein within the sorghum kernel is similar to that of other cereal grains. The peripheral vitreous area of the kernel is rich in protein; interior areas have smaller amounts of protein. Microscopic observations show that protein bodies make up the major part of sorghum endosperm protein.

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H.L. Seckinger

Papers

Sorghum protein ultrastructure as it relates to composition