from American Brewers’ Review
With the present compulsory lowering of gravities the question of head retention has become a somewhat acute one, wherefore a careful consideration of those factors which favorably inﬂuence the production of a clinging foam may at this juncture prove of more than ordinary interest. Illustrative of what the brewer should aim for is the familiar effect obtained by beating the white of an egg, and whatever may be said about viscosity determining head-retention, it is very certain that the one wort constituent that possesses this power above all others is albumose; but this colloid of nitrogen origin, while rendering unequalled service in the direction indicated, may, when in certain forms or when in excess, exert an unfavorable influence upon the brilliancy and stability of the beer—which clearly shows what a complicated question this matter of the vegetable albumens is. In practice probably the best method of steering between the Scylla of bad head retention and the Charybdis of instability, is that of mashing fairly stiffly and for a comparatively low initial heat of, say, 145° F., then after the expiration of twenty minutes, raising the temperature of the goods rapidly by means of a hot underlet, approaching 200° F., to 158 or 160° F. By such means not only will proteolytic action be encouraged, but the high ﬁnal heat will, in great measure, ﬁx the dextrins, which are of such importance in determining persistent condition, without which the nitrogen colloids would be of little use, since it is only their property of forming the skeleton of the gas bubbles, as it were, that constitutes their contribution to the foaming capacity of the beer, as the carbonic acid gas, for which the breaking down of the dextrins and their subsequent fermentation are responsible, must be present to ﬁll the bubble. Another aid to head retention is common salt, assisting as it does in the digestion of the crude albuminous constituents of the malt, and increasing also, very considerably, the stability of colloidal solutions. With the head retaining capacity of the beers so seriously diminished by reason of their greater dilution, it is all the more important to guard against any risk of the further destruction of the head by the introduction of matters such as oil, which possesses the power of exerting a prejudicial effect in foaming capacity, hence the importance of carefully watching the percentage of oil in any maize used. Over modiﬁed malts, owing to the degradation of the protein, may also be answerable for unsatisfactory head retention. When these low-gravity beers are treated on the chilling and ﬁltering system, it is quite possible that some of the ﬁnely divided colloids responsible for head production may be entrapped by the ﬁlter; it is therefore advisable not to employ too great a pressure in the making of the cakes—in fact, it is preferable to ﬁlter twice through two loosely packed ﬁlters rather than through one packed too tightly—although the matter of yeast removal, as mentioned in the previous note, must not be overlooked.