Premium
THE SEPARATION OF THE PROTEIN CONSTITUENTS OF WORT
Author(s) -
Johnston J. H. St.
Publication year - 1948
Publication title -
journal of the institute of brewing
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.523
H-Index - 51
eISSN - 2050-0416
pISSN - 0046-9750
DOI - 10.1002/j.2050-0416.1948.tb06184.x
Subject(s) - chromatography , separation (statistics) , chemistry , brewing , food science , mathematics , fermentation , statistics
Four fractions have been isolated from wort by fractional precipitation with ammonium sulphate. Protein T is a chill‐sensitive globulin‐tannin compound of isoelectric point about P h 6.4. Protein C is an albumin, readily coagulated by heat or agitation, of isoelectric point about p H 6.0. Protein O, a nucleoprotein, is soluble and heat‐stable above p H 5.0 but is precipitated completely as a red flocculum at its isoelectric point p H 3.9. Fraction D has less marked colloidal properties and probably consists of proteoses associated with dextrins. Protein O is readily formed by oxidation of either uncoagulated or coagulated Protein C, hence its concentration in wort or beer depends on the methods of boiling and cooling and on the extent of exposure to air. Being negatively charged at the P H 4 of wort and beer, Protein O reacts with the other positively charged proteins, causing either turbidity or mutual flocculation. Flocculation of wort after cooling, flocculation of yeast, fining, and most of the non‐biological turbidities and sediments of beer are due to flocculation of the proteins.