COMPARATIVE STUDIES OF METHODS OF HOP ANALYSIS: III. RECENT METHODS OF ANALYSIS FOR α ACIDS AND OTHER RESIN CONSTITUENTS

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Abstract
All four of the newer methods tested (Verzele & Govaert, Gough charcoal, spectrophotometric, and conductometric) are at least as accurate as the established methods. The polarimetric methods appear rather more accurate than the older, established methods and it seems possible that, with improvement in details, the spectrophotometric and conductometric methods may also be more accurate than the older methods. Three of the four methods (Verzele & Govaert, Gough charcoal, and spectrophotometric) can be relied upon to give correct results with old hops, unlike the lead precipitation methods. All four methods are more rapid than the older methods, while the spectrophotometric method and the conductometric method seem to create a new class of ultra-rapid methods. From the studies made, which have included a careful survey of the solvents required, it appears that some of the chief remaining sources of error may be in the initial grinding and weighing of the hops. As a possible alternative to mill grinding, it is suggested that the “polythene bag” method might be used in the Ford & Tait and Gough charcoal methods.

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