On the basis of results of recent investigations of factors affecting beer stability, It is possible to make recommendations of procedures which will favour the produc tion of stable beer. The troublesome /9-globulin cannot be eliminated from barley during malting, but acidification of the mash to the isoelectric point of this protein (pH 4-9) gives encouraging results. Closed cooling systems favour stability, and avoidance of contact between the fermented beer and air is of the first importance. Kieselguhr is appropriate for pre-flltration, but centrifuging is not advisable when high stability is desired unless the problem of heating during treatment can be solved. Sheet filters alone should not be used for beers intended for pasteurization, but pulp filters are more efficient in removing chill-haze materials. Foaming properties are dependent on materials different from those responsible for nonbiological stability, so that theoretically it should be possible to improve stability without impairing foaming, though at present the differential treatment necessary to achieve this cannot be realized to the full.

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Volatile sulphur compounds, particularly hydrogen sulphide and mercaptans, are normal products of yeast metabolism. Although they tend to be purged out of beer during fermentation and maturation, it is not uncommon for finished beer to retain enough of them—up wards of 0·02 ppm as sulphur—to impair its aroma. The addition of a small amount of copper sulphate to sulphury beer cleanses its aroma by transforming volatile sulphur into non‐volatile copper sulphide and mercaptides, but since a considerable proportion of this added copper is liable to be inactivated by complexing with nitrogenous constituents of the beer, the removal of sulphur may necessitate the addition of so much copper as to threaten the shelf life of the beer. It has been found that not only may traces of copper be dosed electrolytically into beer with great precision but that the copper so dosed reacts nearly quantitatively with the volatile sulphur present, thus abolishing the latter with no appreciable increase in the net copper content of the beer. The process has given satisfactory results on an industrial scale, improving the flavour of beers without prejudice to their other characteristics.

Overfoaming is a highly undesirable defect which may make its appearance in bottled beer which has been subjected to the vicissitudes of transportation from brewery to consumer. It is most probable that vibration during transport, acting in conjunction with certain abnormal constituents of the beer (presumably derived from the barley), causes the formation of innumerable minute nuclei which in turn occasion the violent evolution of carbon dioxide as soon as the bottle is opened. The application of controlled shaking is widely used as a laboratory method of evoking overfoaming and so of assessing the liability of a beer to this defect. It has been discovered that the presence of cobalt (in the form of simple cobaltous salts) at a concentration of 0–2‐10 parts per million parts of beer entirely, or almost entirely, abolishes its liability to overfoam. Whilst this concentration of cobalt also improves foam stability and foam adhesion, it is without effect on the taste and stability of the beer and is unobjectionable from the point of view of public health. The hypothesis is proposed that cobalt, by complexing with certain nitrogenous constituents of the beer, produces surface‐active substances which Inactivate the nuclei responsible for overfoaming.

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