Nitrogenous Constituents of Brewing Materials: Viii. Fractionation of the Nitrogen Compounds of Worts and Beers. Foam-Stabilizing Activity of the Fractions

Abstract

Hopped and unhopped infusion worts and the derived beers have been fractionally precipitated by means of metallic salts in presence of ethanol at various pH values using modifications of the methods used by Cohn and later by Schmid for blood serum proteins. The final solution obtained after removing the various precipitates was found to contain only a small proportion of the undialysable nitrogen compounds originally present, and it was submitted to the ion‐exchange procedures described earlier in this Series. In this way, the whole of the nitrogen was accounted for. The various protein fractions were mixtures and, in addition, contained polysaccharide. It is perhaps significant that, with the exception of a precipitate produced by chilling alone, no fraction contained an amount of polyphenol comparable with that normally encountered in beer haze. The precipitated fractions contained the bulk of the foam‐stabilizing activity of the original materials, this activity being confined to fractions amounting to less than 14% of the total solutes.

‘Foam-Loving’ Complex Nitrogen Materials in Beer

“…However, it is generally agreed that only a portion of the total complex-nitrogen present in whole beer is involved.4-' The nature of the 'foamloving' materials comprising this portion has now been re-investigated using the technique of isoelectrophoresis.9 Experimental All-malt beers were prepared by a standard procedure on the pilot scale10 and fraction ated according to the modified Cohn pro cedure of Davies el al. 3 Isoelectrophoresis in thin layers of Sephadex gel, and treatments of fractions with silica-gel, were carried out as described previously.10 Foam-tower fractionation.-The method of 'foam-tower fractionation' used to generate and separate beer foam was a modification of that described by Gray & Stone,4 the prin cipal difference being that oxygen-free nitro gen was used to gas the beer instead of carbon dioxide. This change resulted in the pro duction of very stable foam which permitted generation at relatively low gas pressure (3-4 psi at start) and consequently slow flow rates.…”