DOI: 10.1094/CC-83-0099 |  VIEW ARTICLE

Interaction Between Sorghum Protein Extraction and Precipitation Conditions on Yield, Purity, and Composition of Purified Protein Fractions.

S. R. Bean (1,2), B. P. Ioerger (1), S. H. Park (1), and H. Singh (3). (1) USDA-ARS, Grain Marketing and Production Research Center, Manhattan, KS 66502. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. (2) Corresponding author. Phone: 785-776-2725. Fax: 785-537-5534. E-mail: <scott.bean@gmprc.ksu.edu> (3) California State University, Los Angeles, CA, 90032. Cereal Chem. 83(1):99-107. Accepted October 25, 2005. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. AACC International, Inc., 2006.

Sorghum proteins have the potential to be used as a bio-industrial renewable resource for applications such as biodegradable films and packaging. This project was designed to evaluate the effect of interactions between sorghum protein extraction and precipitation conditions on the yield, purity, and composition of sorghum protein fractions. Proteins were extracted with 70% ethanol under nonreducing conditions, with ultrasound, or under reducing conditions using either sodium metabisulfite or glutathione as the reducing agent. Several conditions were used to isolate the extracted proteins through precipitation, including lowering ethanol concentrations alone or in combination with lowering to pH 2.5, or by adding 1M NaCl to the extract. Combinations of these conditions were also tested. All precipitation conditions effectively precipitated proteins and lowering the pH and adding 1M NaCl to the extracts enhanced precipitation in some cases. However, the conditions that precipitated the maxium amount of protein or highest purity of protein varied according to how the proteins were initially extracted. Precipitated proteins were characterized by RP-HPLC, SEC, HPCE, and SDS-PAGE to compare the protein fractions composition. Nonreduced and sonicated samples had a much wider M(w) distribution than reduced extracts. Thus, extraction and precipitation conditions influenced the isolated proteins yield, purity, and composition. Because the extraction and purification processes influenced the composition, purity, and biochemical properties, it may be possible to prepare protein fractions with unique functionalities for specific end-uses.