PILOT SCALE BREWING TRIALS WITH SEEDLESS YEOMAN AND ZENITH HOPS

Beers of sound flavour and quality have been produced on the pilot-scale using the new hop cultivars, Yeoman and Zenith.     

COMMERCIAL BREWING TRIALS WITH ZENITH HOPS

Commercial brewing trials with Zenith hops from the 1982 and 1983 crops have shown that these hops are suitable for producing both ales and lager beers.     

THE STORAGE OF YEOMAN HOPS AND PELLETISED POWDERS

Studies have shown that on extended storage of up to 90 weeks at ambient temperature pockets of Yeoman hops lose α-acids less rapidly than do the other varieties of English hops which are rich in resins. As expected the rate of loss of α-acids is further reduced when Yeoman hops are stored in the cold. Pelletised powders made from Yeoman hops show excellent storage characteristics when commercial packs are kept for 12 months either at ambient temperature or in the cold.     

INSTITUTE OF BREWING HOPS ADVISORY COMMITTEE ANALYSIS OF HOPS OF THE 1972 CROP

Analytical values for 14 varieties of hops from the 1972 crop are presented in relation to the district of production. The tendency noted in 1971 for the variation within growths to diminish was continued in 1972. It was found that for Keyworth's Mid-season a sampling rate of 1 in 20 would be acceptable for commercial purposes.     

THE STORAGE OF WYE TARGET HOPS: ADDENDUM: STORAGE OF FIFTEEN GROWTHS OF WYE TARGET HOPS OVER 12 MONTHS

Wye Target hops lose both α-acids and bittering potential when stored at ambient temperature. Although there is some variation in the rate that different growths lose α-acids, such losses can be substantially reduced by storing Wye Target hops in the cold.     

THE EFFECT OF STORAGE TEMPERATURE ON THE STABILITY OF THE ALPHA-ACIDS CONTENT OF BALED HOPS

The α-acids content of baled hops (Pride of Ringwood) stored at ?20°C, ?5°C, +5°C and +22°C was monitored over a twelve month storage period. The α-acids content of the hops was found to decrease at a linear rate, i.e., by zero order kinetics, at each storage temperature. The relationship between reaction rate and storage temperature was found to accord with the predictions of classical reaction kinetics, enabling a prediction of the stability of hops stored at various temperatures to be made.     

ANALYSIS OF HOPS AND HOP PRODUCTS FOR α-ACIDS OR ISO-α-ACIDS

Two methods based on the resolution of mixtures of hop compounds by chromatography on Sephadex columns have been adopted by E.B.C. and A.S.B.C. as ‘International Methods’.     

KINETICS OF HOP STORAGE

After an initial ‘delay period’ the storage losses of α- and β-acids follow a first-order rate equation and not a zero-order equation as has been suggested by others.     

QUANTITATIVE ANALYSIS OF HOPS AND HOP EXTRACTS BY HIGH PRESSURE ION EXCHANGE CHROMATOGRAPHY

A new analysis for hop acids in hops and hop extracts is described. It is based on recent developments in high pressure liquid chromatography using pellicular anion exchange column filling material. Quantitative evaluation of α-acids, β-acids and oxidation products in hops and hop extracts is carried out by standard addition of pure humulone. The α-acids are completely separated from other hop substances before quantitation. The results of α-acids determinations must therefore be more accurate than was formerly possible and they are compared with conductometric titration results which are systematically higher. This is to be expected as it becomes more and more obvious that paper strip and conductometric analysis are not selective enough and determine fractions as “α-acids” which are in fact oxidation products of the hop acids.     

STABILITY OF RESINS IN PELLETISED HOPS

The α-acids content and Lead Conductance Value of hop pellets, manufactured from seedless Pride of Ringwood hops grown in Australia and stored at 5°C, 20°C or 30°C, were monitored over a twelve month storage period. No decrease in α-acids content occurred during storage at 5°C, whereas at 20°C the decrease (ca. 7%) was approximately one-third that experienced for baled hops of the same variety. At both 5°C and 20°C the Lead Conductance Value decreased at approximately one-third the rate of that in baled hops. During twelve months storage at 30°C the α-acids content of the hop pellets decreased by approximately 40% and the Lead Conductance Value by 30%. The hop pellets stored at 20°C and 30°C developed rancid odours during the twelve months storage period.     

VACUUM PACKAGING OF NEW ZEALAND HOPS

Three cultivars of New Zealand hops were packaged in two ways, vacuum and non-vacuum, and stored at two temperatures, 0°C and ambient. Over the 38 week test period the degradation of Lead Conductance Value was linear for all treatments with no difference between cultivars and no evidence of a ‘safe’ or ‘delay’ period. The degradation coefficient [Lead Conductance Value (%)/week] was highest for non-vacuum packed, ambient (?0·151), followed by non-vacuum packed refrigerated (?0·077), vacuum packed ambient (?0·039) and vacuum packed refrigerated (?0·012).     

AUTOMATED REPORTING ON THE QUALITY OF HOPS AND HOP PRODUCTS

The quality of a hop variety or a hop product can readily be assessed by a fully automated sequence of selective extraction, fractionation and quantitative analysis. To illustrate the elegance of the method, nine hop varieties and three hop extracts were compared with respect to the content of important marker compounds in the hop oils and of the hop acids. Supercritical fluid extraction at different densities of carbon dioxide was applied to extract selectively, the hop oils and the hop acids, respectively. The hop oils were further fractionated into an apolar and a polar fraction by solid phase extraction and consecutive elution with n-hexane and ethyl acetate. Separation and identification were achieved by capillary gas chromatography coupled to mass spectrometry. Myrcene, β;-caryophyllene, α;-humulene and β;-farnesene in the apolar fraction, linalool, undecan-2-one, tridecan-2-one and humuladienone in the polar fraction were selected for quantitative evaluation of the respective hop oils. Sulphur-containing compounds were revealed by capillary gas chromatography using sulphur-selective atomic emission detection. Complete separation and quantification of all hop α;-acids and β;-acids was effected by microemulsion electrokinetic chromatography coupled to diode array detection .     

HOP INDUSTRY COMMITTEE: ANALYSIS OF HOPS OF THE 1977 CROP

Analytical values for α-acid content of thirteen varieties of hops from the 1977 crop are presented in relation to the district of production. For all varieties the tolerance aim of ±0.5% was easily achieved, the whole crop being less variable than in any previous year since these records were kept. The results are acceptable for commercial purposes. α-Acid values for seedless hops from Hampshire and from the Seedless Hop Trials are included and comparisons with seeded hops are shown over a three year period.     

ENZYMIC DEGRADATION OF α-ACIDS IN HOPS

Evidence is presented for the biological oxidation of α-acids in hop cones by an enzyme having molecular weight 17,000 daltons, K_m 6–0 and Mn as the active metal ion. The enzyme is located in bracts and bracteoles and not in lupulin glands. The presence of an endogenous inhibitor was demonstrated. The specific activity of protein in hop cones increased with maturity and this was probably associated with release of α-acids from lupulin glands.     

ANALYSIS OF HOPS OF THE 1986 CROP

Analytical values for α-acid content of twelve varieties of hops from the 1986 crop are presented in relation to the district of production. The variabilities of Wye Northdown, Zenith and Wye Challenger follow similar trends to those of previous years, while Northern Brewer has continued to show a reduction in variability. Following the increase in sampling rate, Yeoman has reverted to an acceptable level of variation. Fuggle, Progress and Bramling Cross have increased their variabilities but remain within acceptable limits. The variabilities of Goldings, W.G.V. and Wye Target, despite the increase in sampling rate of the latter, have attained higher than normal levels. The sampling rates have been considered and in view of the adverse growing conditions encountered with the 1986 crop, no changes have been recommended.     

ANALYSIS OF HOPS OF THE 1987 CROP

Analytical values for α-acid content, as measured by lead conductance value, of twelve varieties of hops from the 1987 crop are presented in relation to the district of production. Satisfactory variabilities have been achieved by Fuggle, Progress, Bramling Cross, Northern Brewer, Zenith, Wye Challenger and Omega. Wye Northdown has increased in variability, reaching the upper limit of acceptability despite an increase in sampling rate. Goldings, W.G.V. and Wye Target have continued to show higher than normal variabilities. This year Yeoman has moved in variability above the acceptable limit. The sampling rates have been considered and in view of the unusual growing conditions experienced with the 1987 crop, with hop yields considerably reduced and α-acids increased to very high levels, no changes have been recommended.     

ANALYSIS OF HOPS OF THE 1985 CROP

Analytical values for α-acid content of twelve varieties of hops from the 1985 crop are presented in relation to the district of production. With the exception of the varieties Zenith, Wye Target and Yeoman, the variability of the crop gave a similar trend to that of previous years. The sampling rates have been considered and increases in the rates for Wye Target and Yeoman have been recommended.     

INSTITUTE OF BREWING HOPS ADVISORY COMMITTEE BREWING TRIALS WITH WYE CHALLENGER,WYE TARGET AND NORTHERN BREWER HOPS

The Wye Challenger hops brewed in the 1972 trial had higher α-acid contents but produced similar bitterness (EBU's) when brewed at similar α-acid-into-brew rates as Northern Brewer hops. On average the Wye Challenger hopped beers drunk slightly less bitter than the Northern Brewer hopped beers but, overall, drinkers indicated no preference between these beers. The Wye Target hops used in the 1972 trial came from four growths of varying α-acid contents. However, at similar α-acid-into-brew rates as used for Northern Brewer hops similar levels of bitterness (EBU's) were obtained. On average, the drinkers thought the Wye Target hopped beers drank slightly less bitter but were equally preferred on general flavour grounds to the Northern Brewer hopped beers. All breweries thought Wye Challenger, Wye Target and Northern Brewer suitable as a copper hop for at least up to 50% of the hop grist.     

HOP INDUSTRY COMMITTEE ANALYSIS OF HOPS OF THE 1984 CROP

Analytical values for α-acid content of thirteen varieties of hops from the 1984 crop are presented in relation to the district of production. For all varieties, except Yeoman, the tolerance aim of ±0·5% was achieved. The production of Yeoman has almost doubled this year and the inclusion of young hops with mature hops in some growths has led to increased within growth variation and failure of this variety, by a small margin, to remain within the limits of the tolerance aim. Apart from this, the variability of the crop compared well with previous years and the results are acceptable for commercial purposes. The sampling rates have been considered and no changes have been recommended.     

HOP INDUSTRY COMMITTEE ANALYSIS OF HOPS OF THE 1982 CROP

Analytical values for α-acid content of fourteen varieties of hops from the 1982 crop are presented in relation to the district of production. For all varieties the tolerance aim of ± 0.5% was achieved this year and variability of the crop was generally the same as the average for the last five years. As before, the results are acceptable for commercial purposes. The sampling rates have been considered with no change recommended.