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United States Department of Agriculture

Agricultural Research Service

Research Project: ENHANCED END USE QUALITY AND UTILIZATION OF SORGHUM GRAIN

Location: Grain Quality and Structure Research Unit

2008 Annual Report


1a.Objectives (from AD-416)
Determine relationships between sorghum grain physical properties including hardness, diameter, and kernel weight, protein and starch composition and processing quality and identify sorghum biochemical components related to food functionality and bio-industrial uses such as ethanol production. Use knowledge of these components to improve the quality and yields of bio-industrial materials and the quality and functionality of sorghum flour which will facilitate development of new, high quality foods, especially for the gluten free food market.


1b.Approach (from AD-416)
New slope and bias curves for measuring hardness, diameter, weight and moisture of sorghum grain by the SKCS will be determined for more accurate characterization of sorghum using the SKCS. Differences in protein content and composition of isolated hard and soft endosperm fractions will be determined. Sample sets to be used for relating processing quality to protein content and composition will be collected. Samples varying in pericarp color, presence of testa layer, plant color, and kernel attributes for analysis of grain color compounds, phenolics, and other small molecules will be collected. Techniques for extracting and analyzing sorghum color compounds by HPLC and HPLC-MS will be developed.

Multi-instrument SKCS comparisons and calibrations with researchers in Kansas, Nebraska, and Texas will be completed. The effect of environment on protein content and composition of isolated hard and soft endosperm fractions will be determined. Wet milling, dry milling, extrusion and fermentation quality of selected sorghum lines will be conducted. Color compounds, phenolics, and other small molecules in sorghum from weathered and sound grain; evaluate grains for markers of insect and fungal damage and infestation will be characterized and cataloged.

Exotic germplasm will be evaluated for desirable processing traits (e.g. ethanol yield). GxE stability of processing quality in sorghum lines showing desirable processing traits will be evaluated. Impact of compounds found in sorghum grains as a result of weathering, mold, insects, or fungal invasion on food and processing quality will be determined. Processing methods to reduce or eliminate impact of environmental damage will be investigated.

Improved techniques for extracting and analyzing sorghum proteins will be developed. Methods for extracting and purifying sorghum proteins for industrial and food applications will be determined. Formulations for the production of wheat free sorghum foods from batter type systems will be optimized.

Optimization of batter type product formulations for production of wheat free sorghum based foods will be continued. Visco-elastic dough formation in artificial sorghum protein-starch dough systems will be investigated and changes to sorghum proteins during mixing will be elucidated and compared to wheat proteins during mixing. Methods for disruption of sorghum protein bodies in sorghum flour to free proteins for interaction during mixing will be developed. Starch and protein content and composition from diverse sorghum lines will be determined and related to ethanol and lactic acid yields. The extent of protein-protein interaction and protein-starch interaction in artificial sorghum dough systems will be determined. Methods for the use of reduction-oxidation systems to form a visco-elastic dough directly from sorghum flour will be developed. Sorghum proteins and starch will be modified to improve functionality in food. Pre-treatment methods for altering protein and starch composition in sorghum for improved ethanol and lactic acid yields will be developed.


3.Progress Report
Sorghum based food production: A visco-elastic dough was made from zein proteins, which are biochemically similar to the storage proteins from sorghum. The mechanism of dough formation was investigated as was bread quality from this dough. In addition research was conducted on the effect of processing on the functionality of both zein and kafirin. A second visco-elastic dough made from carob germ proteins was also successfully produced and the bread quality from this system evaluated. In addition, the carob germ proteins were characterized using methods typically used to analyze wheat gluten to provide insight into the mechanism of dough formation. Carob proteins were found to have polymeric proteins with a molecular weight distribution much smaller than that of wheat and that the carob protein subunits were much larger than those found in sorghum. Preliminary work was conducted on using a carob-sorghum flour mix to produce wheat-free tortillas. This research supports ARS Strategic Plan Goal # 2 “Enhance the competitiveness and sustainability of rural and farm economies” via the actionable strategy “Improve understanding of relationships between raw material/feedstock composition, component molecular structure/physical structure, and end-use quality, function and end-user acceptance.”

Fermentation quality of sorghum: The effect of mashing on sorghum protein cross-linking and its relationship to fermentation quality of sorghum was conducted. Lines that showed more cross-linking tended to have lower fermentation efficiencies (i.e. took longer to reach maximum ethanol yields). Based on this research, a fraction of polymeric proteins were identified as markers that could be used to predict ethanol fermentation efficiency in sorghum. This research supports ARS Strategic Plan Goal # 2 “Enhance the competitiveness and sustainability of rural and farm economies” via the actionable strategy “Improve understanding of relationships between raw material/feedstock composition, component molecular structure/physical structure, and end-use quality, function and end-user acceptance.”


4.Accomplishments
1. Impact of mashing on sorghum proteins

Sorghum is a drought resistant cereal crop grown in the central U.S. The majority of the U.S. sorghum crop is currently used for animal feed. However, increasing amounts are being used for fuel ethanol production. For ethanol plants located in the sorghum growing region of the U.S., sorghum is the major feedstock. During ethanol production, the starch in cereal grains is converted to glucose and then fermented to ethanol. This process involves heating the material (mashing), during which sorghum proteins form cross-links. These cross-links form web-like structures that trapped starch and reduced fermentation efficiency. Identifying sorghum lines that do not develop strong protein cross-links may lead to the development of improved sorghum hybrids for the ethanol industry. This research supports ARS Strategic Plan Goal #2 "Enhance the competitiveness and sustainability of rural and farm economies" via the actionable strategy "Improved understanding of relationships between raw material/feedstock composition, component molecular structure/physical structure, and end-use quality, function and end-user acceptance" and NP306 "Quality and Utilization of Agricultural Products" Component 1. Quality characterization, preservation, and enhancement, problems a-c.


5.Significant Activities that Support Special Target Populations
None.


6.Technology Transfer

Number of Non-Peer Reviewed Presentations and Proceedings4

Review Publications
Schober, T.J., Bean, S., Boyle, D.L. 2007. Gluten-free sorghum bread improved by sourdough fermentation: Biochemical, rheological and microstructural background. Journal of Agricultural and Food Chemistry. 55:5137-5146.

Ciacci, C., Maiuri, L., Caporaso, N., Bucci, C., Del Giudice, L., Massardo, D., Pontieri, P., Fonzo, N., Bean, S., Ioerger, B.P., Londei, M. 2007. Celiac disease: In vitro and in vivo safety and tolerability of wheat-free sorghum food products. Clinical Nutrition. 26:799-805.

Ioerger, B.P., Bean, S., Tuinstra, M.R., Pedersen, J.F., Erpelding, J.E., Lee, K.M., Herrman, T.J. 2007. Characterization of polymeric proteins from vitreous and floury sorghum endosperm. Journal of Agricultural and Food Chemistry. 55:10232-10239.

Taylor, J., Bean, S., Ioerger, B.P., Taylor, J. 2007. Preferential binding of sorghum tannins with gamma-kafirin and the influence of tannin binding on kafirin digestibility and biodegradation. Journal of Cereal Science. 46:22-31.

Wang, D., Bean, S., Mcclaren, J., Seib, P., Madl, R., Tuinstra, M., Shi, Y., Lenz, M., Wu, X., Zhao, R. 2008. Grain Sorghum is a Viable Feedstock for Ethanol Production. Journal of Industrial Microbiology and Biotechnology. 35:313-320.

Wu, X., Zhao, R., Bean, S., Seib, P.A., Mclaren, J.S., Madl, R.L., Tuinstra, M., Lenz, M., Wang, D. 2007. Factors impacting ethanol production from grain sorghum in the dry-grind process. Cereal Chemistry. 84(2):130-136.

Zhao, R., Bean, S., Ioerger, B.P., Wang, D., Boyle, D.L. 2008. Impact of Mashing on Sorghum Proteins and Its Relationship to Ethanol Fermentation. Journal of Agricultural and Food Chemistry. 56:946:953.

Last Modified: 7/31/2014
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