here - the 34th European Brewery Convention

P59
Monitoring the appearance and composition of lupulin glands during maturation up to and
beyond harvest
Jane Birkby 1 , Katarzyna Wolinska 1 , Keith T Westwood 1
1 Barth Innovations Limited, Tonbridge, United Kingdom
Many factors determine the optimum date for harvesting hops. The decision relies on the experience
of the grower and it is rare for more objective (expensive) analytical methods to be used. The
application of a simple, inexpensive analytical procedure would give the growers more insight into the
maturity of the crop and aid the decision when to harvest. In this study two varieties of hops were
monitored, up to and beyond harvest date. The appearance of the lupulin glands was observed using
a simple microscope and the hops analysed for alpha acids, oil content and composition. As the crop
developed, lupulin glands changed and when a dark, opaque tip appeared this was a good indication
for optimum harvesting. At this point the oil content was significantly higher than at time of harvest,
whilst the alpha acid levels remained fairly stable. It appears that for the particular growths monitored,
the hops were harvested 10-12 days too early for optimum flavour impact.
P60
Influence of picking date on the Hop Storage Index (HSI)
Sandro Cocuzza 1 , Rasso Hiltmann 2 , Maximilian Krause 2
1 Hopsteiner, Mainburg, Germany, 2 TUM Weihenstephan, Freising, Germany
HSI is one of the parameters to evaluate freshness of hops and hop products. Upper control limit
values for hop purchasing are often set up in the range of 0.35 to 0.45. Fresh harvested hops are
assessed to have an HSI around 0.25.
Internal analyses of fresh harvested hops over the last crop years indicated both inconsistent initial
HSI for all varieties within the same crop year and also varying values within one variety over several
years. To clarify if picking date influences the initial HSI, standardized harvesting trials were performed
in cooperation with the Research Centres at Hüll and Weihenstephan. Samples of 3 aroma and bitter
varieties from 2 locations were taken over an extended period around the regular picking date.
The results show that HSI increases with later picking date. For the evaluation of hop freshness,
annual and varietal fluctuations should be considered and therefore the increase of HSI from its initial
value ("Δ-HSI") is more suitable than fixed values.
P61
Gushing induced by hop acid components - importance in various beers and beverages
Brian Buffin 1
1 Kalsec, Inc., Kalamazoo, United States
The occurrence and control of gushing is an important quality factor. Efforts to identify gushing
promoters have focused on barley degradation, and, to a lesser extent, hop constituents.
The use of pre-isomerized hop acids, including reduced forms, continues to increase. We previously
reported the results from a study that evaluated the impact of advanced hop products on gushing in
high-volume American lagers. The existence and importance of hop acid induced gushing has now
been evaluated in different carbonated and malt beverages. It was shown that the nature of the
beverage has a dramatic impact on the presence and extent of gushing. Research was conducted to
identify the influence of hop acids, hop processing, beverage type, and dosing levels. Experimental