Sunflower Protein Concentrates and Isolates. The Removal of Polyphenols and Phytic Acid and a Study of the Binding of Chlorogenic Acid
Saeed, Mohammad
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https://hdl.handle.net/2142/70098
Description
Title
Sunflower Protein Concentrates and Isolates. The Removal of Polyphenols and Phytic Acid and a Study of the Binding of Chlorogenic Acid
Author(s)
Saeed, Mohammad
Issue Date
1987
Doctoral Committee Chair(s)
Cheryan, Munir
Department of Study
Food Science
Discipline
Food Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Food Science and Technology
Abstract
The objectives of this research were to determine the effect of various processing treatments such as dehulling, solvent extraction, aqueous extraction and centrifugation on sunflower proteins and to develop methods for the removal of polyphenols and phytic acid from the sunflower products. An attempt was also made to elucidate the nature and extent of interaction of phenolic compounds with sunflower proteins.
Dehulling and defatting did not appreciably reduce polyphenols or phytic acid. Solvent extraction of the defatted meal with acidic butanol reduced the polyphenol concentration to less than 0.05% with minimum denaturation of proteins as evidenced from the nitrogen solubility profile of the resultant low-polyphenol protein concentrate (LPC). LPC contained 70% protein (dry basis) and has a good potential in food applications as it does not turn brown under alkaline conditions.
The large differences in solubility profiles of phytic acid and protein were used to remove phytic acid from the defatted meal. A reduced-phytate protein concentrate (RPC) was prepared by extraction at pH 5 and centrifugation. RPC contained 75% protein and had improved protein solubility but developed a brown color at alkaline pH. A reduced-phytate protein isolate was prepared and had improved protein solubility but was brown in color because of binding of oxidized phenolic compounds.
A low-polyphenol, reduced-phytate protein isolate (LPRP) was prepared and has excellent potential in food applications. Not only does it have good functional properties (stable white color, high protein solubility), but also significantly better nutritional properties due to the removal of polyphenols and phytic acid.
The interaction of chlorogenic acid with the LPRP sunflower protein isolate was investigated.
Binding studies were done at three ligand:protein molar ratios and at four pHs. The pH had a profound influence on the extent of binding. The molar binding ratio was lowest at pH 5, irrespective of ligand:protein molar ratio. Above a certain free chlorogenic acid concentration, binding at pH 9 was higher than at other pHs.
Binding of chlorogenic acid to sunflower protein increased as the ligand:protein molar ratio increased irrespective of pH. Two nonidentical groups of binding sites were found on sunflower proteins at all pHs except pH 9 where three nonidentical groups of binding sites were observed. (Abstract shortened with permission of author.)
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