Location: Grain Quality and Structure Research2021 Annual Report
OBJECTIVE 1: Determine and quantify grain components linked to ‘health-promoting’ benefits and commercial quality of sorghum foods and feed. • Subobjective 1.A. Determine the mechanism related to the reduced protein quality of cooked sorghum flour. • Subobjective 1.B. Characterize protease inhibitors in sorghum and their role in modulating digestibility in sorghum flour. • Subobjective 1.C. Evaluate and identify bioactive compounds in sorghum linked to anti-cancer and other health promoting properties. OBJECTIVE 2: Develop and improve methodologies for rapid prediction and measurement of sorghum grain attributes linked to valuable end-use quality traits. • Subobjective 2.A. Utilize UHPLC (ultra-high-performance liquid chromatography) size exclusion for characterizing sorghum polymeric protein complexes related to end-use quality of sorghum. • Subobjective 2.B. Develop near infrared spectroscopic methods to predict grain composition and quality traits of sorghum.
Sorghum is an important drought tolerant crop in the central U.S. where water is limited and rainfall unpredictable. Sorghum has been primarily used for animal feed in the U.S. and is consistently used by the biofuel industry and increasingly used in human foods. As for any cereal, grain composition plays an important role in its utilization. To support utilization of sorghum grain, research is needed that identifies grain components linked to functional and nutritional quality of sorghum products. One issue for sorghum utilization is how processing, especially cooking, impacts sorghum flour nutritional and functional properties. It is known that heating increases sorghum protein cross-linking, which in turn affects both protein and starch functionality and digestibility. The exact mechanism of how this occurs is not known; nor is it known how protein and starch changes influence the role of digestive inhibitory compounds in sorghum. Identifying the mechanism behind these changes will provide avenues to improve sorghum flour quality as well as provide new targets to improve sorghum grain composition at the genetic level. Likewise, sorghum is known to have high levels of bioactive compounds that have potential human-health promoting benefits. However, much of the past research on bioactive compounds in sorghum has been based on chemical assays. To further define and identify the health-promoting benefits of sorghum, research using additional methods such as cellular based assays are needed. Such research will help define the value of sorghum in human foods and provide targets for the genetic improvement of sorghum.
The overall goal of this project is to identify grain composition traits related to end-use quality and value of sorghum. The project is completing the first year of its current 5-year plan. Progress this year includes completing research characterizing changes to sorghum proteins when heated which directly relates to Objective 1.A “determine the mechanism related to the reduced protein quality of cooked sorghum flour”. Related research has started that is investigating how different types of fermentation impact protein digestibility in sorghum as well. This research will provide data on how processing sorghum can potentially negate the negative effect of heating on sorghum proteins. Related to Objective 1.C “Evaluate and identify bioactive compounds in sorghum linked to anti-cancer and other health promoting properties” research has encapsulated sorghum phenolic extracts in lecithin-based vesicles for greater bioavailability/delivery, evaluated sorghum extract effects on cytokine signaling to further study the effects of sorghum on inflammatory pathways, and begun to develop additional methods in order to analyze sorghum phenolics in more detail. Substantial research related to Objective 2.B “develop near infrared spectroscopic methods to predict grain composition and quality traits of sorghum” has been completed this year with near-infrared spectroscopy calibration curves well developed for protein content and with calibration curves in development for starch content, amylose content, lysine content, crude fat, and total phenolics as well as discrimination models for waxy sorghum and tannin sorghum. Methods for measuring amylose content in sorghum have been evaluated and compared to provide higher throughput wet chemistry methods to support development of NIR calibrations. Close to 1500 sorghum grain samples were scanned by NIR this year for the sorghum breeding community and sorghum grain composition data has been supplied for two sorghum germplasm releases. Objective 1.C. research evaluating how nitrogen and sulfur fertilization impacts sorghum grain protein and protein digestibility has also been partially completed which demonstrates that crop management can have a large impact on grain quality and supports overall Objective 1 of the project (improving value of sorghum). In addition, research this year has been conducted on using sorghum bran and proteins to produce different types of biomaterials (particles, encapsulating agents, etc.), also supporting the overall objective of the plan to increase the value of sorghum grain.
1. Anti-cancer effect of sorghum polyphons in the colon cancer model. Sorghum polyphenols have been shown to exert an anti-cancer effect in limited cell and animal studies. The mechanisms behind this anti-cancer effect are not well understood and at the same time these mechanisms are important to understand to design further studies including animal and human models. Researchers at ARS in Manhattan, Kansas, in collaboration with University of Maryland, College Park, tested sorghum polyphenol extracts on four different colon cancer cell lines and probed the mechanisms behind the anti-cancer effect. Sorghum polyphenols limited the ability of the cancer to spread to other cells. This study provides justification for further research using animal models and justifies sorghum to be researched as a health food.
2. Anti-inflammatory effect of sorghum polyphenols in macrophage cells. Whole grain consumption is associated with many positive health effects and whole grain sorghum can be a good source of polyphenols. Polyphenols are known to have many human health benefits, typically from their antioxidant properties. However, the polyphenols in sorghum may have an additive beneficial effect by reducing inflammation. ARS scientists in Manhattan, Kansas, in collaboration with the University of Tennessee have demonstrated the antioxidant and anti-inflammatory effect of sorghum polyphenols in macrophage cells. Furthermore, a novel variety of sorghum which was used in this study was grown in both the United States and Mexico. The results demonstrated that high phenolic sorghum grown in the United States has comparable polyphenol and anti-inflammatory properties to the same genotype grown in Mexico. This study will aid in design of more robust studies using sorghum as an anti-inflammatory agent and will also provide information to sorghum breeders on the effects of the growing environment on high phenolic sorghum.
3. Sorghum proteins improve functionality of wheat-free dough made from corn proteins. Isolated corn proteins, zein, is known to be able to form a dough with properties like wheat dough. However, dough made from corn proteins does not produce baked foods with the same quality as wheat-based foods. To improve the quality of wheat-free dough made from corn proteins, ARS researchers in Manhattan, Kansas, collaborated with scientists from South Africa to investigate the ability of sorghum proteins to improve the quality of dough made from corn proteins. When sorghum proteins were added to the corn proteins, the dough formed from the mixed proteins was improved over dough made from corn proteins alone. This research demonstrated that mixtures of corn and sorghum proteins work together to form a better dough which could lead to improved wheat-free baked food products and new commercial opportunities for isolated sorghum proteins.
4. Effect of tempering conditions on white sorghum milling, flour, and bread properties. Sorghum flour is increasingly being used in commercial food products, but limited research has been conducted on optimizing milling conditions and how milling conditions impact sorghum flour quality. To address this issue, ARS researchers in Manhattan, Kansas, collaborated with scientists from Kansas State University to determine how tempering (adding water) to sorghum grain before milling impacted the milling process and sorghum flour quality. Room temperature tempering led to more efficient milling of sorghum grain. Likewise, bread made from flour that was milled after room temperature tempering also had improved bread quality compared to other treatments. Tempering sorghum with room temperature water could be used to improve milling of sorghum and improve quality and value of sorghum-based baked products.
5. Impact of sorghum genetics and grain treatment on nutritional quality of injera. Injera is a fermented flat bread that is widely consumed in Africa and is often made from sorghum. Improving the nutritional quality of injera would help reduce malnutrition in Sub-Saharan Africa and development of high quality injera could provide a novel fermented food for markets in the United States. ARS researchers in Manhattan, Kansas, collaborated with researchers at Kansas State University to evaluate the nutritional quality of injera made from different sorghum varieties along with grain pretreatment steps (dry roasting, sprouting, and removing the outer layers of the grain) and milling flour to different particle sizes. Injera made from sprouted sorghum improved the protein digestibility and increased overall protein percentage, demonstrating that processing of sorghum grain before fermenting into injera could improve sorghum nutritional quality.
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Perumal, R., Morris, G.P., Jagadish, K., Little, C.R., Tesso, T., Bean, S.R., Yu, J., Tuinstra, M.R. 2021. Registration of the Sorghum [Sorghum bicolor (L.) Moench] Nested Association Mapping (NAM) populations in RTx430 background. Journal of Plant Registrations. https://doi.org/10.1002/plr2.20110.
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Bean, S.R., Akin, P.A., Aramouni, F.M. 2021. Zein functionality in viscoelastic dough for baked food products. Journal of Cereal Science. https://doi.org/10.1016/j.jcs.2021.103270.
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Lampiri, E., Athanassiou, C.G., Arthur, F.H. 2020. Population growth and development of the khapra beetle (Coleoptera: Dermestidae), on different sorghum fractions. Journal of Economic Entomology. 114:424-429. https://doi.org/10.1093/jee/toaa235.
Sydney, S.E., R.G., A., Giovanna, B., Sarah, S., Davina, R., Smolensky, D., Herald, T.J., Ramasamy, P., D. U., T., T. G., N. 2021. Antimicrobial activity of sorghum phenolic extract on bovine foodborne and mastitis causing pathogens. Antibiotics. https://doi.org/10.3390/antibiotics10050594.