Effects of cooking and screw‐pressing on functional properties of Cuphea PSR23 seed proteins

Abstract

This investigation determined the effects of oil processing conditions on some functional properties of Cuphea PSR23 seed proteins to evaluate their potential for value-added uses. Flaked Cuphea seeds were cooked at 82°C (180°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. Protein from unprocessed Cuphea seeds had excellent emulsifying properties, poor foaming properties, poor solubility (10%) at pH 4-7, and much greater solubility at pH 2 and 10 (57 and 88%, respectively). Solubility profiles showed that cooking the flaked seeds to 82°C for 30 min resulted in a 50-60% reduction in soluble proteins. Cooking for 120 min gave <6% soluble proteins at all pH levels. Cooking for 75 min gave good oil yields but also resulted in <10% soluble proteins at pH 2-7 and 25% soluble proteins at pH 10. Seed cooking and screw pressing during oil extraction had significant detrimental effects on the solubility of Cuphea seed protein but generally improved its foaming capacity and emulsifying activity.There is great interest in developing the Cuphea plant as an alternative source of industrial oil. Its seed produces 16-42% oil that is rich in medium-chain FA (MCFA), such as caprylic, capric, lauric, myristic, and palmitic acids (1,2). These MCFA are used in detergents, cosmetics, lubricants, and fuels. The current commercial sources of MCFA are the tropical oilseeds (coconut and palm kernel oils). Cuphea oil has a strong potential to augment or replace these imported sources of MCFA (1).Cuphea, however, has some undesirable agronomic traits that are considered as major deterrents to its domestication and commercialization, including: indeterminate growth and flowering patterns, excessive seed shattering from maturing pods, and the presence of sticky substances on leaves and stems that create harvesting problems (2,3). Domestication studies at Oregon State University (Corvallis, OR) identified C. lanceolata, C. wrightii, and C. viscosissima as the most promising species for cultivation (3,4). Breeding efforts at the same institution produced PSR23, a semidomesticated hybrid from C. lanceolata and C. viscosissima that exhibits partial seed retention on maturity and contains high amounts of capric acid (4). Cuphea PSR23 has been subjected to field testing for the past 5 yr.If Cuphea oil production is successful, then it is anticipated that protein-rich meals will be also be generated because the seed contains as much as 25% crude protein (CP) (2). Current literature on Cuphea reports only the amount of protein in the whole seed. There is no information available on the quality and properties of Cuphea seed proteins. Recently, our research team completed a pioneering study that determined the SDS-PAGE profile, soluble classes, and amino acid composition of Cuphea seed protein. We detected six major subunits, a...

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