17E-3 |
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R. HORAX1, N. S. Hettiarachchy1, and M. Jalaluddin2. (1) Dept. of Food Science, Univ. of Arkansas, 2650 N. Young Avenue, Fayetteville, AR AR 72704, (2) Department of Agriculture, University of Arkansas, Pine Bluff, AR 71611 Cowpea seed contains 20-25% protein and is rich in essential and non-essential amino acids. Extensive information is available on soy protein characteristics and functional properties. However, such information on cowpea protein is limited. The objectives of this study were to prepare protein isolates from cowpea, and compare the characteristics and functionalities of CPI with soy protein isolate (SPI). Protein isolates from cowpea and soybean were prepared under mild alkali condition and the protein contents were quantified by an automatic Kjeldahl method. Amino acid composition and molecular sizes were determined by an amino acid analyzer and electrophoresis, respectively. Hydrophobic fluorescence probe and differential scanning calorimetry were used for hydrophobicity and thermal property, respectively. Protein solubility was determined at varying pH (1.0 increment). Emulsifying and foaming properties were determined by a turbidimetric method, and our laboratory procedure, respectively. Gelation was determined by heating the protein colloidal solution (70-100 oC) followed by cooling (30 min). The protein contents of CPI and SPI ranged from 91.4-91.8% and 93.0-93.5%, respectively. Electrophoretograms showed bands at 60 and 40 kDa for CPI, and 95, 65, 60, 40, and 35 kDa for SPI. CPI had higher valine, phenylalanine, leucine, histidine, and lysine, but lower glycine than SPI. The surface hydrophobicities ranged from 318-567 and 644-661 for CPI and SPI, respectively. CPI and SPI had single and two denaturation temperatures, respectively. Both proteins showed U-shaped curves for solubility. CPI demonstrated lower emulsifying and foaming activites compared with SPI. Gels were formed at 70 oC for 40 and 30 min, respectively, for CPI (12%) and SPI (10%). Cowpea protein isolate needs modification to enhance emulsifying and foaming properties. The modified CPI with enhanced functional properties can be used in a variety of food products where such properties are required.
Session 17E, Food Chemistry: Proteins
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