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Functional Properties of 7s Globulin Extracted from Cowpea Vicilins

¹College of Food Science and Engineering, Inner Mongolia Agricultural University, Hohhot, 010018 PRChina. ²Corresponding author. Phone: 86-0471-4309231. Fax: 86-0471-4309230. E-mail: zhangmeili22@sina.com ³College of Agronomy, Inner Mongolia Agricultural University, Hohhot, 010018 PRChina

The seed of cowpea (Vigna unguiculata L.) is rich in protein and the amino acid profiles of the meal are suitable for human dietary products, but little is known about the structure and chemical properties of the protein extracted from this legume. This study determined the functional properties of two selected cowpea cultivars and their solubility, emulsifying capacity, surface hydrophobicity, and thermal stability. Seeds of red and black cowpea were surface sterilized and the 7s globulin was isolated and purified using column chromatography with Sephacryl S-300 (Hi-Prep 26/60) gel column. Also, SDS-PAGE and protein structure were analyzed using biochemical procedures. At high ionic strength (μ = 0.5), cowpea 7s globulin fraction exhibited better solubility for a wide range of pH levels, higher emulsifying capacities, and greater thermal stability than those obtained at low ionic strength (μ = 0.08). The lowest solubility was observed at pH 5.3–6.4 at the low ionic strength. Emulsifying capacities at high protein concentration were greater when compared with low protein concentration. T_m values of black cowpea globulin fraction were higher than those of red cowpea globulin fraction, whereas the surface hydrophobicity of the globulin fraction in red cowpea was larger than that in black cowpea.