Differences in Utilisation of the Essential Oil of Hops During the Production of Dry-Hopped and Late-Hopped Beers

Abstract

Late‐hopped and dry‐hopped beers were prepared and their lipophilic constituents extracted using Amberlite XAD‐2 resin. Examination of the volatile constituents by GC‐MS confirmed that most of the hop oil added towards the end of wort boiling is lost by evaporation. Part of the material which survives boiling is chemically transformed by yeast during fermentation. Dry‐hopped beer contained compounds more representative of the original hop oil than did the corresponding late‐hopped beer. A liquid carbon dioxide extract of hops, rich in essential oil, has been fractionated by column chromatography on alumina‐silica giving preparations which simulate either late‐hop or dry‐hop character.

Hop Essential Oil: Analysis, Chemical Composition and Odor Characteristics

“…A great deal of research has been invested into developing commercially fractionated hop oil products with specifi c aroma qualities that may be added either pre-or postfermentation ( Haley and Peppard, 1983 ;Westwood and Daoud, 1985 ;Westwood, 1987 ;Gardner, 1994 ;Marriott, 2001 ;Goiris et al ., 2002 ). Isolated hop oil was originally dosed into wort and beer as aqueous emulsions or entrained in a liquid CO 2 stream ( Westwood, 1987 ).…”

Hop Aroma Component Profile and the Aroma Unit

“…They also have found varietal differences in beers brewed with single hop varieties (7)(8)(9). In England, the practice of dry hopping has led to the postfermentation addition of hop oil isolated from liquid carbon dioxide extracts (6). The amounts and composition of such extracts can be controlled fairly easily (27).…”

Use of the Hop Aroma Component Profile to Calculate Hop Rates for Standardizing Aroma Units and Bitterness Units in Brewing

“…Many factors can affect the hop character of a specific beer or ale. Bittering resins and essential oils of hop cultivars vary with the year of harvest, source, plant maturity, conditions at the time of picking, processing procedures, storage conditions, and time of storage (2)(3)(4)(5)(6)(7)(8)(9)14,19,21,26,27). Production variables include the variety and amount of hops used, time and place of addition, kettle boil and evaporation, losses during fermentation and filtration, tank blowdowns to reduce air content, taste panel perceptions, laboratory analysis, and packaging materials, specifically crown liners (2,6,8,14,(17)(18)(19)23,27).…”

“…Because hopping rates are traditionally based on bittering value (a-acids analysis) (27), such rate changes will provide uniformity only in final product bitterness. Therefore, when using aroma hops to impart a specific hop character of uniform intensity, which comes from the hop oil components and quantitatively changes independently of bittering values (6,12,13,15,20,21,27), it seems reasonable that aroma hopping rates should also be quantitatively adjusted to produce a beer with a more uniform hop character.…”

“…So far, the only hopping procedure that addresses this quality problem is the postfermentation injection of hop resins and oils, most recently obtained with the use of liquid carbon dioxide (2,3,6,(12)(13)(14)20,22,23,27).…”