EVALUATION OF HOPS. I. A REVIEW

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Abstract
The hop resins, to which may be ascribed the bittering characters of hops and the contribution of hops to the biological stability of beer, represent a complex mixture containing few well‐defined components. It seems indisputable that the bacteriostatic materials are to be found in the soft‐resins, though the active materials in the original hops do not pass unchanged to beer; the active principles in beer represent resin transformation products, those derived from humulone being of particular significance. The numerous chemical and physicochemical methods available for attempting to determine the potential bacteriostatic potency of hops include gravimetric methods based on differential solvent extraction or lead‐salt precipitation, titrimetric, colorimetric and polarimetric methods, methods involving chromatographic separation, and ultra‐violet and infra‐red spectroscopy. However, such methods fail to give predictions of unequivocal utility owing to the complexity of the changes occurring during storage and during the brewing process. More reliance can be placed on microbiological methods and on trial brews, but the majority of such methods at present available are either of uncertain accuracy or are difficult of application.

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