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COMPARATIVE STUDIES OF METHODS OF HOP ANALYSIS: II. ESTIMATION OF HUMULONE AND OTHER RESIN CONSTITUENTS
Author(s) -
Bishop L. R.
Publication year - 1955
Publication title -
journal of the institute of brewing
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.523
H-Index - 51
eISSN - 2050-0416
pISSN - 0046-9750
DOI - 10.1002/j.2050-0416.1955.tb02821.x
Subject(s) - preservative , hop (telecommunications) , fraction (chemistry) , wax , coprecipitation , chemistry , chromatography , organic chemistry , computer science , computer network
The basis of hop resin analysis has been carefully considered in order to decide which analyses are of primary significance to the brewer. The α‐ fraction or humulone group comprises humulone, cohumulone and adhumulone, which are closely allied chemically and can be estimated as a group. The β‐fraction includes lupulone (which is without preservative or bittering value in beer produced by the usual processes) together with variable amounts of α‐ and β‐soft resins, some of which contribute to the pre‐formed wort‐soluble bittering materials in hops. There is the possibility of measuring these latter constituents, but no generally recognized method exists. Chief attention has therefore been given to the estimation of the α‐fraction. Collaborative studies have shown good agreement between the results obtained by the older and the newer methods of analysis for this group. The sources of error in each method are more important than the differences between them. The errors found are:—(a) With all methods, including column methods, e.g ., that of Govaert ' Verzele, danger of destruction of soft resins by oxidation and sunlight. (b) With the Wöllmer, the Ford ' Tait and the Walker ' Hastings methods: (i) high results obtained by the use of impure methyl alcohol; (ii) low results obtained with old hops; and (iii) incorrect results obtained because of the difficult lead‐precipitation endpoint. (c) With the Ford ' Tait method, the danger of high results for humulones caused by coprecipitation of waxes.If these errors are eliminated, the results agree well. The origin of the remaining small differences is still the subject of discussion. Thus, provided the appropriate precautions are taken, any of the above four methods can be employed.