Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/8/2006
Publication Date: 9/1/2006
Citation: Evangelista, R.L., Wu, Y.V., Hojilla-Evangelista, M.P. 2006. Characterization of proteins in Cuphea (PSR23) seeds. Journal of the American Oil Chemists' Society. 83(9):785-790.
Interpretive Summary: Cuphea is an annual crop native to the Americas that is being developed as an alternative source of medium-chain fatty acids (MCFA) which are used in detergents, cosmetics, lubricants, fuels and food applications. The current commercial sources of MCFAs are coconut and palm kernel oils or derived from petroleum. Cuphea seed contains up to 35% crude oil. The defatted meal contains as much as 33% crude protein. Currently, the seeds are processed mainly for their oil to support research needs, as well as for product development and testing. Basic information on the quality and properties of Cuphea seed proteins is lacking or not available in the literature. This study was conducted to determine some properties of Cuphea seed protein, such as solubility, soluble classes, and amino acid composition. We found that most of the proteins are extracted at pH 10 and above. We also found that the alkaline-soluble proteins are the dominant class in the protein extract. Compared with the ideal protein, Cuphea seed proteins have lesser amounts of essential amino acids. However, the alkaline-soluble proteins extracts contained higher amounts of essential amino acid than that of the whole seed proteins. Our study provides the first information on the size, amino acid quality, soluble classes and solubility behavior of Cuphea proteins. These findings will benefit industry and academic researchers in identifying value-added uses for Cuphea.
Technical Abstract: This study characterized the proteins in Cuphea (PSR23) seed to provide fundamental information on their size, amino acid profile, soluble classes, and solubility behavior. The seed contained 32% (dry basis, db) oil and 21% (db) crude protein. Over 70% of the protein was extracted at pH 11.6. Nonprotein nitrogen accounted for 9% of the total N content. PSR23 seed protein had sufficient amounts of methionine + cysteine, considerable amounts (90%) of valine, phenylalanine + tyrosine, but was devoid of tryptophan. Lysine was the second most limiting essential amino acid at 68%. Glutelins and albumins accounted for 83.5% and 15.4%, respectively, of the total protein extracted. SDS-PAGE showed that Cuphea protein subunits had MW ranging from <6.5 to 110 kDA. Dominant protein subunits in albumins had MW of 30, 40, 50 and 86 kDA. Glutelins had two major protein subunits with MW of 15 and 30 kDA. The distribution of essential amino acids was better in the albumins and glutetelin fractions than in the defatted meal.