Novel vegetable protein fractionization process and compositions

Abstract

According to the invention a novel vegetable protein fractionation procedure is disclosed which includes a straightforward process to obtain β-conglycinin-rich and glycinin-rich isolated protein fractions with unique functional and nutritional properties desired by the food industry. The process is much simplified compared to the art and avoids multiple steps in the usual fractionation of soy protein and uses very small amounts of salts avoiding the necessity of excessive washing and desalting steps. The process yields high amounts of protein fractions with high isoflavone contents and improved functional properties.

1 . A β-conglycinin-enriched protein extract provided by the method comprising:
 obtaining a defatted vegetable protein source; 
 extracting said source with a dilute alkali with a pH of approximately 7 to approximately 11 to form a mixture of the proteins present in said vegetable source; 
 obtaining a supernatant protein extract from said mixture, by adding a combination of a source of calcium to achieve an amount of from about 5 mM to about 10 mM calcium ions, and a reducing agent of sulfur dioxide to achieve an amount of sulfur dioxide of from about 5 mM to about 10 mM to form a slurry, wherein said combination of calcium and sulfur dioxide fractionating agents eliminate an intermediate fraction; and 
 adjusting the pH of said slurry to a pH of approximately 7 to approximately 5 to obtain a precipitate which is enriched in glycinin and a supernatant which is enriched in β-conglycinin as compared to percentages of each protein in the original mixture. 
 
     
     
         2 . An glycinin-enriched protein precipitate provided by the method comprising:
 obtaining a defatted vegetable protein source;   extracting said source with a dilute alkali with a pH of approximately 7 to approximately 11 to form a mixture of the proteins present in said vegetable source;   obtaining a supernatant protein extract from said mixture, by adding a combination of a source of calcium to achieve an amount of from about 5 mM to about 10 mM calcium ions, and a reducing agent of sulfur dioxide to achieve an amount of sulfur dioxide of from about 5 mM to about 10 mM to form a slurry, wherein said combination of calcium and sulfur dioxide fractionating agents eliminate an intermediate fraction; and   adjusting the pH of said slurry to a pH of approximately 7 to approximately 5 to obtain a precipitate which is enriched in glycinin and a supernatant which is enriched in β-conglycinin as compared to percentages of each protein in the original mixture.   
     
     
         3 . The product of  claim 1 , wherein said defatted vegetable source is obtained through screw pressing and/or Gas-Supported Screw Pressing (GSSP) and/or other mechanically oil extraction method, such as extruding-expelling, that produces a defatted vegetable source and further comprising the steps of: extracting said source with a dilute alkali of pH of about approximately 7 to approximately 11 to form a mixture of proteins present in said vegetable source; obtaining a supernatant oil-rich “cream” fraction and a supernatant protein extract from said mixture; and subjecting said protein extract to said fractional precipitation methods. 
     
     
         4 . The product of  claim 2 , wherein said defatted vegetable source is obtained through screw pressing and/or Gas-Supported Screw Pressing (GSSP) and/or other mechanically oil extraction method, such as extruding-expelling, that produces a defatted vegetable source and further comprising the steps of: extracting said source with a dilute alkali of pH of about approximately 7 to approximately 11 to form a mixture of proteins present in said vegetable source; obtaining a supernatant oil-rich “cream” fraction and a supernatant protein extract from said mixture; and subjecting said protein extract to said fractional precipitation methods. 
     
     
         5 . A product produced by the method consisting of:
 obtaining a full-fat vegetable protein source;   extracting said source with a dilute alkali of pH of about approximately 7 to approximately 11 to form a mixture of proteins present in said vegetable source;   obtaining a supernatant protein extract from said mixture,   subjecting said supernatant to fractional precipitation with a combination of a multi-valent salt selected from the group consisting of calcium or EDTA, wherein said salt is added in an amount sufficient to achieve from about 5 mM to about 10 mM of ions, and a reducing agent of sulfur dioxide to form a slurry, wherein said combination of the multi-valent salt and sulfur dioxide fractionating agents eliminate an intermediate fraction; and   adjusting the pH of said slurry to a pH of approximately 7 to approximately 5 to obtain a precipitate, which is enriched in glycinin, and a supernatant, which is enriched in β-conglycinin, as compared to the percentages of each protein in the original mixture.   
     
     
         6 . The product of  claim 5  further comprising the step of drying said β-conglycinin-rich soy milk to create a β-conglycinin-rich soy milk powder. 
     
     
         7 . The product of  claim 5 , wherein said product is a glycinin-rich and fiber-rich soy protein product. 
     
     
         8 . A soy protein composition comprising a β-conglycinin content between about 50% and about 90% of the protein and a glycinin content between about 10% and about 50% of the protein, wherein the total isoflavone content in the composition is greater than 1.5 mg/g on a dry weight basis. 
     
     
         9 . A soy protein composition comprising a glycinin content between about 50% and about 90% of the protein and a β-conglycinin content between about 10% and about 50% of the protein, wherein the total isoflavone content in the composition is greater than 1 mg/g on a dry weight basis.