Impact of Hop Freshness on Dry Hopped Beer Quality

Abstract

The hop plant is seasonal, but beer production continues throughout the whole year. The quality of hops begins to decrease immediately after harvesting; therefore, maintaining the highest possible quality is important. A good indicator of hop freshness is the hop storage index (HSI). In this study, three different varieties of hops with five different HSI values, from 0.3 to 0.7, were used for brewing with the dry hopping technique. The main goal was to evaluate the impact of the HSI value on beer quality in terms of hop aroma and bitterness. Alpha acids, iso-alpha acids, humulinones, bitterness units and hop aroma compounds were chemically analysed. Sensorial analysis was also conducted on all samples. Decreases in the intensity and quality of hop aroma were detected with increasing HSI. The quality of bitterness was also reduced. High HSI also led to undesirable gushing. Beers brewed with hops with HSI values greater than 0.4 had deviations in aroma and bitterness when compared with beers brewed with fresh hops.

The Impact of Hop Freshness on Kettle-Hopped Beers

“…The difference observed for the alpha-terpineol content with increasing HSI was not statistically significant, but the levels were above the sensorial threshold, meaning that alpha-terpineol did contribute to aroma. As observed with the dry hopping technique, the contents of beta-citronelol and nerol did not follow any clear pattern [3]. The geraniol content declined with increasing HSI and then plateaued at a certain point.…”

“…The differences in the contents of volatiles were smaller than those observed after dry hopping [3] and were most noticeable during sensorial evaluation. The samples that were boiled for 5 min contained a higher amount of myrcene only for the samples with HSI 0.3; otherwise, the myrcene content was the same regardless of the age of the hop.…”

“…Aged hops also affect the colour of the beer and increase its cost, as the brewing must be prolonged to achieve the same content of iso-alpha-acids in the beer. The most comprehensive investigation thus far, conducted by Rutnik et al at the Slovenian Institute of Hop Research and Brewing [3], compared three different hop varieties with five different HSI values in terms of chemical and sensorial properties, but they used only a dry hopping technique. We concluded that, with dry hopping, hops with high HSI values lowered the beer quality in terms of aroma and bitterness.…”

“…Humulinones are more soluble than iso-alpha-acids due to the presence of an additional hydroxyl group, and they are also 34% less bitter [7]. According to Shellhammer et al [8] and Rutnik et al [3], they do not impart a bad quality of bitterness to beer.…”

Effects of Dry-Hopping on Beer Chemistry and Sensory Properties—A Review

“…The authors suggested that the maximum HSI for hops intended for dry-hopping should be less than 0.5. The authors also found that hops with a HSI above 0.6 can cause gushing [ 52 , 93 , 95 , 98 ].…”