Mashing – Aeration

From The Brewers’ Journal  –  July 1917

MASHING – AERATION
by Matthew J. Cannon, F.C.S

Opinions differ widely as to the best manner of mashing brewers’ grist, and modern developments, both in the milling machinery and in the internal fittings of the mash-tun have always been the subject of criticism. Sometimes the criticism, destructive rather than constructive, has tended to upset the views which were formerly held by brewers of life-long experience. There are some of us young enough to remember the practical brewer who knew that the proper means of making a mash was by means of a primitive oar, worked by the brewer himself. But we have progressed since those days. It is nearly fifty years ago since it was recognized that an external mixer was essential to successful mashing if a uniform mixture was to be secured in the mash-tun. But, even so recently as thirty years ago there were a number of breweries, certainly of the smaller kind, which relied upon a somewhat haphazard method of mixing, the mash-tun being un-provided with either an out-side masher of the Steele type or internal rakes. In certain cases, the mash-tun was un-provided with any appliance for mixing. Although today the employment of outside mashing machines is practically universal, various opinions have been put forward which appear to question their utility and economy. From some points of view the external mixer must be regarded as a makeshift appliance , not because it is inefficient in itself, but on account of its clumsy performance falling short of modern requirements. One of the defects of the modern external mixer is the limitation of the degree of thickness and the temperatures which can be employed in making up the mash. No doubt the possible limits of the water-malt ratio available in ordinary practice do not entail any wide variation in the compensation of the wort constituents, but the mechanical defect exists, and is likely to cause trouble if not kept under close control. When employing the assistance of machinery in making a mash, there are two objectives to be kept in view. It is desired to effect a preliminary admixture of the grist and mashing liquor at a uniform temperature and to prevent “balling,” or formation of lumps. In connection with both these points one has always to take into account that the modern grinding machinery has resulted in the production of a finger grist which requires more careful handling. It is certainly a matter well worth careful consideration whether the existing external mashing machine, devised primarily to deal with coarse grist, is altogether adapted to the exigencies of present-day necessities.

One of the greatest aids to healthy fermentation is aeration. This point is frequently neglected in brewery procedure, and sometimes the assistance which is casually given is lacking at the moment when it is most needed. If the yeast is to do its work efficiently, it is essential that a proper degree of aeration be induced at each of the separate stages of the brewing process. We need not refer to the many beneficient changes which result from aeration anterior to the mash-tun stage. After the copper stage the use of aeration becomes all-important from the point of view of the progress of fermentation, the up-keep of the yeast stock and the stability of the beer. Before collection in the fermenting tun it is essential that close attention be given to hot and cold aeration during the cooling stage. The former has an important influence in eliminating undesirable nitrogenous and resinous matters from the wort; the latter representing oxygen mechanically absorbed or dissolved by the wort is absolutely indispensable to the development of the yeast organism at the initial stages of fermentation and immediately after pitching. Hot aeration, to be effective, should take place at temperatures between 200 deg . F. and 160 deg . F. For certain purposes the optimum temperature for hot aeration ranges between 180 deg . to 170 deg . F. To secure hot aeration practice and science has adopted many means, or endeavored to suit existing plant to the known requirements. The hop-back, the cooler, the mash-tun and the refrigerator have each had their exponents as the only means of securing the desired degree of aeration. Frequently, however, in the many contradictions which have accompanied the statement of experience of type of plant, the real issue has been overlooked. Underlying the employment of the hop-back, the cooler and the refrigeration, the  principle of aeration is supreme. Questions of filtration, deposition of sludge, and cooling of the wort are subsidiary matters from the standpoint of regular fermentations, vigorous and healthy yeast and sound beers.

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