|Wu, Y - FORMER ARS|
Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 23, 2008
Publication Date: February 20, 2009
Citation: Hojillaevangelist, M.P., Evangelista, R.L., Wu, Y.V. 2009. Characterization of Milkweed Seed Proteins. Industrial Crops and Products. 29(1):275-280. Interpretive Summary: Milkweed (Asclepias spp.) is a perennial weed that thrives in the U.S. Corn Belt. The common milkweed (Asclepias syriaca) is familiar to the general public as the food source for monarch butterflies. Milkweed is also an industrial crop; its seed pods provide the floss that is used in the commercial production of hypoallergenic fillers in comforters and pillows. The seeds end up as by-products production and have limited applications as plants for landscaping and erosion control. Milkweed seed contains substantial amounts of oil (21%) and protein (32%). The oil is similar in quality to soybean oil, but there is no information on the properties of milkweed protein. These properties should be examined to identify other possible value-added uses of the seed protein. Our study determined some chemical properties, such as the size (molecular weight, MW) of the major fractions and soluble classes of milkweed seed proteins, as well as, functional properties to help us identify potential applications of the seed protein. We detected eight distinct low-MW fractions present in the whole seed protein. We found that the dominant protein classes were soluble in water (22%) and dilute salt (15%). We noted that milkweed seed protein had high solubility (more than 40%) at pH 7 or higher (alkaline conditions). We found that the seed protein produced substantial but unstable foams, showed excellent emulsifying capacity, formed stable emulsions, and had satisfactory water-holding capacity. Our findings suggest that milkweed seed protein has strong potential for a broad range of applications in food and nonfood systems. Our pioneering study on the composition and functional properties of milkweed seed protein provides fundamental data that could be used by other researchers from universities and industry to define the optimal conditions for extraction and recovery of milkweed seed proteins. Our findings can also assist in identifying and developing novel uses for seed proteins, thus enhancing the value of the milkweed crop.
Technical Abstract: Milkweed (Asclepias spp.) is a crop grown mainly for the production of floss used as hypoallergenic fillers in comforters and pillows. The seeds end up as by-products. Milkweed seed contains 21% oil and 30% crude protein (dry basis). The oil is similar in quality to soybean oil, but there is no information on the properties of milkweed protein. This study determined the MW of major fractions, soluble classes, and functional properties of milkweed seed protein. Ground milkweed seeds were analyzed for proximate composition, as well as, subjected to SDS-PAGE and protein functionality tests. Reduced proteins showed eight distinct bands with MW ranging from 6.5 to 59.3 kDa. The dominant protein classes were water- (22%) and salt-soluble (15%). Solubility of milkweed seed protein was lowest (12%) at pH 4, 40% at pH 7, and reached a maximum (60%) at pH 10. The protein produced substantial foam volumes, but foam stability was poor. Its emulsifying capacity was excellent, especially at pH 10, and emulsions formed were stable. Water-holding capacity and surface hydrophobicity index values were higher at pH 7 than at pH 10. These results showed that milkweed seed protein has functional properties that may find use in food and nonfood applications.