Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2006
Publication Date: 6/1/2006
Citation: Hojillaevangelist, M.P., Evangelista, R.L. 2006. Effects of cooking and screw-pressing on functional properties of Cuphea PSR23 seed proteins. Journal of the American Oil Chemists' Society. 83:(8):713-718.
Interpretive Summary: Cuphea is an annual crop native to the Americas that is being developed as an alternate source of industrial oil. Cuphea seed contains 16-42% oil that is rich in medium-chain fatty acids (MCFA). These MCFAs are used in detergents, cosmetics, lubricants, and fuels. The current commercial sources of MCFAs are the tropical oils (coconut and palm kernel oils). Cuphea oil has the potential to augment or replace these imported sources of MCFAs. If Cuphea oil production is successful, then it is anticipated that protein-rich meals will also be generated because the seed contains as much as 25% crude protein. However, there is no information currently available on the quality and properties of Cuphea seed proteins. Our study was conducted to determine the functional properties of Cuphea seed protein, how they were affected by the oil processing conditons, and what possible uses Cuphea meal may have in value-added applications. We detected six distinct protein fractions comprising the whole seed protein and noted that these sub-units showed signs of stability against the heat treatment applied during oil processing. We found that Cuphea seed protein had the highest solubility (almost 90%) at pH 10, which implied that the protein may have some use in applications having alkaline environments, such as wood adhesives. However, heating during seed cooking and screw-pressing resulted in significant reduction in solubility of Cuphea seed protein, which would limit the usefulness of press cakes from oil processing. We determined that Cuphea seed protein had poor foaming properties, but foaming capacity was markedly improved by heating during oil processing. We found that Cuphea protein's emulsifying activity was similarly improved by cooking and screw-pressing, but emulsion stability was reduced. Our pioneering study on the functional properties of Cuphea protein from seed and oil processing meal provides fundamental information that could be used by other researchers from academia and industry to define the conditions for optimal extraction and recovery of Cuphea proteins, as well as, identify and develop novel uses for the protein-rich meal from oil processing that would enhance the value of the Cuphea crop.
Technical Abstract: This investigation determined the effects of oil processing conditions on some functional properties of Cuphea PSR23 seed proteins' potential for value-added uses. Flaked Cuphea seeds were cooked at 82 deg C (180 deg F) for 30, 75 or 120 min in the seed conditioner, and then screw-pressed to extract the oil. Cooked flakes and press cakes were analyzed for proximate composition and protein functional properties. Results were compared with those of unprocessed ground, defatted Cuphea seeds (control). Control Cuphea protein had excellent emulsifying properties but poor foaming properties. Control Cuphea protein had poor solubility (10%) at pH 4-7, but at pH 2 and 10, its solubility was 57 and 88%, respectively. Solubility profiles showed that cooking the flaked seeds to 82 deg C for 30 min resulted in 50-60% reduction in soluble proteins. Cooking for 120 min gave less than 6% soluble proteins at all pH levels. Cooking for 75 min gave maximum oil yields, but also resulted in less than 10% soluble proteins at pH 2-7 and 25% soluble proteins at pH 10. Oil extraction conditions had significant detrimental effects on the solubility of Cuphea seed protein, but generally improved its foaming capacity and emulsifying activity.