Molecular Structure and Functionalities of Protein Isolates Prepared from Defatted Cottonseed Flour Succinylated at Various Levels

Authors

  • Y. R. CHOI,

    1. Authors Choi, Lusas, and Rhee are affiliated with the Food Protein Research & Development Center, Texas A&M Univ., College Station, TX 77843–2476.
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  • E. W. LUSAS,

    1. Authors Choi, Lusas, and Rhee are affiliated with the Food Protein Research & Development Center, Texas A&M Univ., College Station, TX 77843–2476.
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  • K. C. RHEE

    1. Authors Choi, Lusas, and Rhee are affiliated with the Food Protein Research & Development Center, Texas A&M Univ., College Station, TX 77843–2476.
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  • This research was funded in part by the Natural Fibers and Food Protein Commission of Texas and in part by the Agricultural Research Service, U.S. Dept. of Agriculture.

  • Sheryl Sadler provided technical assistance for this research.

ABSTRACT

Protein isolates were prepared from glandless cottonseed flour succinylated at various levels. Succinylation levels of the resultant proteins followed first order kinetics with respect to succinic anhydride concentration added. Succinylation decreased the amount of free sulfhydryl, as well as ξ-amino groups of proteins, but did not change intermolecular disulfide bonds. Protein isolate prepared from highly succinylated flour consisted of one homogeneous protein agglomerate, while isolate from unmodified flour contained several heterogeneous proteins. Water solubility of the isolates increased logarithmically with respect to degree of succinylation, with the sharpest increase at 95% succinylation or higher. Heat coagulability had an inverse-linear relationship with amounts of negative charges on protein molecules. Emulsion capacity and oil absorption capacity were not significantly changed at less than 60% succinylation. However, these increased markedly at greater than 60% succinylation. Emulsion capacity had a positive, but not linear correlation with water solubility of proteins.

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