Protein body formation in the starchy endosperm of developing Sorghum bicolor (L.) Moench seeds

Chemical analyses and transmission electron microscopical observations were carried out on developing Sorghum bicolor (L.) Moench seeds to determine when and how protein bodies are formed in the starchy endosperm tissue. Protein bodies were first visible at the milk stage and by late hard dough they completely filled the sub-aleurone cells. Between these stages of development there was an almost linear increase in the amount of prolamin protein in the seed. The protein bodies appeared to grow within envelopes of rough endoplasmic reticulum. It is, therefore, suggested that protein bodies in S. bicolor are formed as a result of prolamin polypeptides being synthesized on the ribosomes on the outside of the envelopes and then passing directly into the lumen of the rough endoplasmic reticulum. This mode of protein body formation is identical to that which takes place in the seeds of another member of the Panicoideae subfamily, viz., Zea mays L.Chemiese analises en transmissie-elektronmikroskopiese waarnemings is uitgevoer op Sorghum bicolor (L.) Moench saad om vas te stel wanneer en op watter wyse proteïenliggame ontstaan in die styselhoudende endospermweefsel. Proteïenliggame het vir die eerste keer sigbaar geword gedurende die melkstadium en toe die hardedeeg stadium bereik is, het die liggame die sub-aleuroonselle volledig gevul. Tussen hierdie ontwikkelingstadia was die toename in prolamin proteïen van die saad amper liniêr. Dit het gelyk asof die proteïenliggame gegroei het binne omhulsels van die growwe endoplasmiese retikulum. Die volgende teorie word dus voorgestel: Proteïenliggame in Sorghum bicolor ontwikkel as gevolg van prolamin polipeptiedsintese deur ribosome wat op die buitekant van die omhulsel geleë is, die proteïenliggame beweeg dan reguit na die lumen van die growwe endoplasmiese retikulum. Hierdie tipe van proteïenliggaamsintese is identies aan die sintese wat plaasvind in die sade van ’n ander lid van die Panicoideae subfamilie, nl. Zea mays L

Protein biofortified sorghum : effect of processing into traditional African foods on their protein quality

Protein biofortification into crops is a means to combat childhood protein-energy malnutrition (PEM) in developing countries, by increasing the bioavailability of protein in staple plant foods and ensuring sustainability of the crop. Protein biofortification of sorghum has been achieved by both chemically induced mutation and genetic engineering. For this biofortification to be effective, the improved protein quality in the grain must be retained when it is processed into staple African foods. Suppression of kafirin synthesis by genetic engineering appeared to be superior to improved protein digestibility by chemical mutagenesis, because both the lysine content and protein digestibility were substantially improved and maintained in a range of African foods. For the genetically engineered sorghums, the protein digestibility corrected amino acid score was almost twice that of their null controls and considerably higher than the high protein digestibility sorghum type. Such protein biofortified sorghum has considerable potential to alleviate PEM.The Bill and Melinda Gates Foundation, Grand Challenges in Global Health Initiative.http://pubs.acs.org/JAF

Cereal biofortification : strategies, challenges and benefits

Under-nutrition is a key underlying cause of the 10 million child deaths each year—most of which are preventable and most of which occur in poor countries. The major direct causes of under-nutrition in poor developing countries are insufficient food intake and an unbalanced diet caused by lack of variety in available foods coupled with disease outbreaks. This study shows that the majority of children living in rural Burkina Faso are severely undernourished as a result of the low amount of food they consume, their lack of dietary diversity, and, consequently, their low intake of many macro- and micronutrients. Replacement of normal cereal staples with biofortified crops would not affect the amount of food consumed per se. However, the strategy of most biofortification programs is to add nutrients to the most profitable and highest yielding varieties available, which would address, to some extent, the issue of insufficient food availability. For biofortified cereals to make a broad impact on the nutritional status of undernourished children in rural Africa, ideally the predominant cereals consumed should be enhanced with multiple critical nutrientsThe Bill and Melinda Gates Grand Challenges 9, Africa Biofortified Sorghum (ABS) Project through a sub-grant from the Africa Harvest Biotechnology Foundation International.http://www.aaccnet.org/publications/plexus/cfw/pastissues/2012/Pages/CFW-57-4-0165.asp

Role of γ-kafirin in the formation and organization of kafirin microstructures

The possible importance of the cysteine-rich γ-prolamin in kafirin and zein functionality has been neglected. The role of γ-kafirin in organized microstructures was investigated in microparticles. Residual kafirin (total kafirin minus γ-kafirin) “microparticles” were non-discrete (amorphous mass of material), as viewed by electron microscopy and atomic force microscopy. Adding 15% γ-kafirin to residual kafirin resulted in the formation of a mixture of non-discrete material and nanosize discrete spherical structures. Adding 30% γ-kafirin to the residual kafirin resulted in discrete spherical nanosize particles. Fourier transform infrared spectroscopy indicated that γ-kafirin had a mixture of random-coil and β-sheet conformations, in contrast to total kafirin, which is mainly α-helical conformation. γ-Kafirin also had a very high glass transition temperature (Tg) (≈270 °C). The conformation and high Tg of γ-kafirin probably confer structural stability to kafirin microstructures. Because of its ability to form disulfide cross-links, γ-kafirin appears to be essential to form and stabilize organized microstructures.Joseph Anyango is grateful for the provision of a University of Pretoria Postdoctoral Fellowship.http://pubs.acs.org/journal/jafcauhb201

Cereal food technologies - India and Africa trends and the need for collaborative and networking programmes

India and Africa share many common food trends such as rapid urbanization and a growing demand for convenience and health-promoting foods.Notably in Africa, these food demands are currently being met by relatively simple value addition to grains through small and medium enterprises.However, achieving improved staple food security will require more complex technologies, higher technical skills and a better organized food pipeline. Thus, in Asia and Africa there is an acute need for collaborative and network programmes in grain science and technology. The recent creation of an ICC India Task Force to make India-International grain science collaboration and networking a reality is a critical step to achieving these goals.http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1757-837

Improvement in water stability and other related functional properties of thin cast kafirin protein films

Improvement in the water stability and other related functional properties of thin (<50 µm) karirin protein films was investigated. Thin conventional kafirin films and kafirin microparticle films were prepared by casting in acetic acid solution. Thin kafirin films cast from microparticles were more stable in water than conventional cast kafirin films. Treatment of kafirin microparticles with heat and transglutaminase resulted in slightly thicker films with reduced tensile strength. In contrast, glutaraldehyde treatment resulted in up to a 43% increase in film tensile strength. The films prepared from microparticles treated with glutaraldehyde treatment were quite stable in ambient temperature water, despite the loss of plasticizer. This was probably due to the formation of convalent crosslinking between free amino groups if the kafirin polypeptides and carbonyl groups of the aldehyde. Thus, such thin glutaraldehyde-treated kafirin microparticle films appear to have good potential for use as biomaterials in aqueous applications.J.O.A. acknowledges a University of Pretoria Postgraduate Research Support Bursary.http://pubs.acs.org/JAF

Improvement of zein dough characteristics using dilute organic acids

The replacement of gluten in dough products poses a major challenge. Preparing zein doughs in dilute acetic acid and lactic acid, such as produced during sourdough fermentation, was investigated. Increasing acid concentrations (0.7, 1.3 and 5.4% [v/v]) increased zein extensibility and reduced the stress and related parameters. Preparation of zein-maize starch/- rice doughs in dilute organic acids improved dough properties to the extent that the doughs could hold air and be inflated into a bubble by Alveography. Further, they exhibited similar Stability (P), Distensibility and deformation energy (W) to wheat flour dough. Confocal laser scanning microscopy revealed an ordered linear fibril network in zein and zein-rice flour doughs prepared in the dilute acids, which became uniform with increasing acid concentration. SDS-PAGE showed that the acids did not hydrolyse or polymerise the zein. FTIR indicated that the acidic conditions slightly increased the proportion of α-helical conformation in the zein doughs, possibly as a result of deamination. This conformational change may be responsible for the considerably improved zein dough properties. Zein doughs prepared in dilute organic acids show potential as a gluten replacement in gluten-free formulations.http://www.elsevier.com/locate/jcshb201

Formation of a viscoelastic dough from isolated total zein (α-, β- and γ-zein) using a glacial acetic acid treatment

Only predominantly α-type zein (commercial zein) has been shown to form a viscoelastic dough. In maize zein comprises α-, β-, γ- and δ-zein (total zein). Because glacial acetic acid can fully solubilise zein, its effect was investigated. Dissolving total zein (comprising α-, β-, γ- and δ-zein)_ in glacial acetic acid and casting a film, enabled a viscoelastic dough to be formed with water above zein’s Tg. The dough was stronger and less extensible than commercial zein dough made without film formation. When residual acetic acid was removed from the total zein film, a dough still formed.. CLSM showed that the total zein dough fibrils were shorter and less well-aligned than those of commercial zein dough and appeared as particles. Disulphide bond cross-linking was probably responsible, for total zein dough stiffness. FTIR showed that total zein wet doughs and total zein slurry with water were predominantly β-sheet, indicating that β-sheet conformation was not directly responsible for dough formation. It is suggested that acetic acid brings about chemical changes in zein, enabling it to better interact with water molecules, counteracting disulphide bonding effects, allowing total zein to form a dough. This is the first report of viscoelastic dough formation from total zein.B.L King is grateful for the provision of South African National Research Foundation and University of Pretoria bursaries.http://www.elsevier.com/locate/jcs2017-09-30hb2017Food Scienc

Roles of protein, starch and sugar in the texture of sorghum biscuits

This study investigated why biscuits made from sorghum flour have a similar texture to wheat biscuits despite the absence of gluten in sorghum dough. Electron microscopy revealed that the sorghum prolamin protein bodies remained intact in the sorghum biscuits and hence were unlikely to contribute to biscuit structure and texture. Polarized light microscopy showed that the starch granules in the sorghum biscuits were not gelatinized. Increasing dough water content increased the breaking strength and brittleness of sorghum biscuits. However, increasing the proportion of pre-gelatinized sorghum flour in the dough reduced the breaking strength of the sorghum biscuits, indicating that starch gelatinization weakened the biscuit structure. In contrast, increasing the sucrose content of the dough increased sorghum biscuit breaking strength and brittleness. At 20% sucrose (flour basis), the sorghum biscuits had similar breaking strength and brittleness to both Marie and sugar-snap wheat biscuits. DSC and X-ray diffractometry showed that the sugar in both the sorghum and wheat biscuits was in the glassy state and polarized light microscopy revealed that the sugar glass embedded or enveloped the sorghum biscuit flour particles. It is concluded that this sugar glass matrix is responsible for the strength and cohesiveness of the sorghum biscuits.The South African National Research Foundationhttp://www.elsevier.com/locate/lwthj2022Consumer ScienceFood Scienc

Protein quality and physical characteristics of Kisra (fermented sorghum pancake-like flatbread) made from tannin and non-tannin sorghum cultivars

Kisra is a naturally lactic acid bacteria- and yeast-fermented sorghum thin pancake-like flatbread produced in Sudan. Kisra has considerable potential as the basis for development of a gluten-free sandwich wrap. To help direct cultivar selection for commercial production of these products, two white, tan plant non-tannin Type I, one white Type II tannin, and one red Type III tannin sorghum cultivars were evaluated with respect to kisra protein quality and physical characteristics. Kisra from the non-tannin sorghums were flexible and had an open-textured structure with many regular gas cells, whereas those from the tannin sorghums were more brittle, denser in structure, and contained far fewer and smaller gas cells. Kisra from the tannin sorghums had the lowest reactive lysine content, in vitro protein digestibility, and Protein Digestibility Corrected Amino Score (PDCAAS), with values being lowest for the Type III sorghum. PDCAAS of kisra from the Type III sorghum was only 0.12, less than half of that from the Type I sorghums. As the tannins in tannin sorghums adversely affect kisra protein quality and physical characteristics, white tan plant, non-tannin sorghum cultivars are most suitable for kisra production and for development of wrap-type sorghum-based baked goods.The South African National Research Foundation for a fellowship for AMAE.http://cerealchemistry.aaccnet.or