Factors affecting sorghum protein digestibility

Publisher Summary
Starch granules range in size from sub-micron elongated granules of chloroplasts to the relatively huge oval granules of potato and canna. Semi-compound granules originate as two or more distinct granules, which then fuse together. Pseudo-compound granules, such as pea starch granules, start out as individual granules, which then develop several large cracks while remaining a single entity. These differences in size and shape make it possible to recognize most of the ordinary food and commercial starches. Starch granules contain small amounts of non-carbohydrate components—lipids, proteins, phosphate, and ash—that affect the behavior of starch in various applications. The tiny starch granules of chloroplasts are important as a temporary carbohydrate reserve and show diurnal synthesis and degradation. Native starch granules show growth rings when observed by optical microscopy, scanning electron microscopy of eroded granules, and transmission electron microscopy of thin sections, especially after chemical treatment. Starches that show prominent growth rings, such as potato starch, require high or saturating water levels for ring visibility.

Chapter vii – organization of starch granules

Publisher Summary This chapter reviews nonmutant starch granule composition and development, and focuses on genetic mutants and how they have been useful in understanding the complexity of polysaccharide biosynthesis and development. Plant species, which are important sources of commercial starch production are focused on, especially maize, because of the many known endosperm mutants of maize, which affect polysaccharide biosynthesis. The information gained applies to other species, and these effects are illustrated in the chapter. General trends in the genetics and physiology of starch development have been illustrated with examples. Starch is a common constituent of higher plants and a source of carbohydrates. Starch in chloroplasts is transitory and accumulates during the light period and is utilized during the dark. Storage starch accumulates in reserve organs during one phase of the plant's lifecycle and is utilized at another time. Starches from reserve organs of many plants are important in commerce. Although considerable effort has been directed at characterizing the enzymes involved in starch synthesis, the role of these enzymes and other factors in determining subtle variations in starch granule structure and starch fine structure remain largely unknown. Variations in granule structure can be associated with plant species, cultivars of a species, the environment in which a cultivar is grown, and genetic mutations.

Genetics and Physiology of Starch Development

The objectives were to characterise the structure and morphology of starch from 17 maize endosperm mutant genotypes in a common Oh43 inbred background to help in understanding the influences of recessive mutant genes on the maize starches

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1145&context=fshn_ag_pubs

Characterization of Starch Structures of 17 Maize Endosperm Mutant Genotypes with Oh43 Inbred Line Background.

Pelleting of broiler diets: An overview with emphasis on pellet quality and nutritional value

Optical microscopy shows that the protein network in endosperm cells of normal corn is composed of an amorphous matrix in which granules averaging about 2 microns in diameter are embedded That these granules are rich in zein is demonstrated by their solubility in 80 percent ethanol High-lysine corn, with submicroscopic granules clearly resolved only in the electron microscope, has a much lower content of zein than normal corn The small size of subcellular protein granules in high-lysine maize as compared with normal corn correlates with the reported difference in zein content of the two types of corn

https://science.sciencemag.org/content/sci/157/3788/556.full.pdf

Subcellular Structure of Endosperm Protein in High-Lysine and Normal Corn

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.

/pdf/sorghum-protein-ultrastructure-as-it-relates-to-composition-334ti9q1et.pdf

Sorghum protein ultrastructure as it relates to composition

Microscopic Characteristics of High‐Amylose Corn Starches

Polarization Colors of Maize Starches Varying in Amylose Content and Genetic Background

Protein either in flour particles or in thin sections spreads on water as a surface dispersion These protein dispersions were transferred to plastics-covered specimen grids and examined by transmission electron microscopy Examinations showed that wheat flour contained lipid which formed small droplets ranging from 001 to 035 μm in diam Protein bodies like those found in immature wheat were not observed in any of the preparations A purified fraction of gliadin contained particles 20 to 80 A in diam representing mol wt between 17 000 and 216 000; whereas a glutenin fraction did not form small particles Protein dispersions from hard and soft wheat had particles 65 to 250 A in diam; hard wheat had smaller particles than the soft wheat Mild treatment with NaHSO3 increased the size of hard wheat protein particles; those in soft wheat did not change much From these observations, hard wheat appears to have compact protein particles which swell in NaHSO3, whereas the structure of soft wheat particles is less dense and they swell in distilled water

M. J. Wolf

Papers

Subcellular Structure of Endosperm Protein in High-Lysine and Normal Corn

Sorghum protein ultrastructure as it relates to composition

Microscopic Characteristics of High‐Amylose Corn Starches

Polarization Colors of Maize Starches Varying in Amylose Content and Genetic Background

Electron microscopy of endosperm protein from hard and soft wheats.