Nutritional compositions from brewers' spent grain and methods for making the same

Abstract

Disclosed herein are embodiments for the isolation of fiber and protein from brewers' spent grain. In some embodiments, the protein has a reduced fat content. In some embodiments, the protein has an improved Protein Digestibility Corrected Amino Acid Score.

1 . A method of preparing protein isolate from brewers' spent grain (BSG), comprising:
 preparing a mixture of BSG in water;   digesting starch in the BSG using an enzyme;   chemical breakdown of carbohydrates by oxidation;   solubilizing the protein to provide a protein solution with insoluble fiber;   removing insoluble fiber from the protein solution with insoluble fiber to provide a protein solution; and   precipitating a protein fraction from the protein solution.   
     
     
         2 . The method of  claim 1 , wherein the protein fraction is dried after precipitation to provide the protein isolate. 
     
     
         3 . The method of  claim 1 , wherein the protein fraction is precipitated from the protein solution by acidifying the protein solution. 
     
     
         4 . The method of  claim 1 , wherein the enzyme used to digest the starch is a starch enzyme. 
     
     
         5 . The method of  claim 1 , further comprising sonicating the BSG in water mixture. 
     
     
         6 . The method of  claim 1 , wherein the insoluble fiber is removed from the solution of solubilized protein using a sieve bend filter with or without recirculation of the solution of solubilized protein. 
     
     
         7 . The method of  claim 1 , wherein the insoluble fiber is removed from the solution of solubilized protein by decanting. 
     
     
         8 . The method of  claim 1 , further comprising treating the protein fraction with hydrogen peroxide thereby providing a protein isolate. 
     
     
         9 . The method of  claim 1 , further comprising treating the protein fraction with a lipophilic solvent to remove fat from the protein fraction thereby providing a reduced fat protein isolate. 
     
     
         10 . A method of isolating protein and/or fiber from brewers' spent grain, comprising:
 digesting the starch in the BSG;   oxidizing carbohydrates;   solubilizing protein;   removing insoluble fiber from a solution of the solubilized protein; and   precipitating the protein.   
     
     
         11 . The method of  claim 10 , wherein the protein is spray dried after precipitation. 
     
     
         12 . The method of  claim 10 , wherein the protein is precipitated by acidifying the solution of the solubilized protein. 
     
     
         13 . The method of  claim 10 , wherein the starch is digested using a starch enzyme. 
     
     
         14 . The method of  claim 10 , wherein the insoluble fiber is removed from the solution of solubilized protein using a DSM filter with or without recirculation of the solution of solubilized protein. 
     
     
         15 . A BSG protein isolate made by the method of  claim 1 . 
     
     
         16 . A BSG protein isolate comprising:
 at least 25% fat;   at least 50% protein.   
     
     
         17 . The BSG protein isolate of  claim 16 , wherein the protein isolate comprises less than 10% fiber. 
     
     
         18 . The BSG protein isolate of  claim 16 , wherein the Protein Digestibility Corrected Amino Acid Score is equal to or at least about 0.98. 
     
     
         19 . The BSG protein isolate of  claim 16 , wherein the BSG based protein isolate includes greater than or equal to 6.6 mg tryptophan/g protein, greater than 25 mg threonine/g protein, 30 mg isoleucine/g protein, 61 mg leucine/g protein, 48 mg lysine/g protein, 23 mg methionine+cysteine/g protein, 41 mg phenylalanine+tyrosine/g protein, 40 mg valine/g protein, and/or 16 mg histidine/g protein. 
     
     
         20 . A nutritional supplement comprising the protein isolate of  claim 16 . 
     
     
         21 . A method of supplementing the diet of a subject, the method comprising providing the subject the nutritional supplement of  claim 20 .