Dynamics of Isomerization of Hop Alpha-Acids and Transition of Hop Essential Oil Components in Beer

Ocvirk, Miha; Košir, Iztok Jože

doi:10.17344/acsi.2020.5394

Cited by 5 publications

(5 citation statements)

References 21 publications

(34 reference statements)

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“…The isomerisation yield of iso-alpha acids is low for two reasons. One is that the solubility of alpha acids is relatively low, so a greater share remains undissolved, and the other is that the temperatures in dry hopping are not high enough for the thermal isomerisation of alpha acids to iso-alpha acids [24]. The humulinones in all three hop samples (Table 2) increased from HSI 0.3 to 0.7, so the same pattern was expected for the beer.…”

Section: Beer Bitternessmentioning

confidence: 64%

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Impact of Hop Freshness on Dry Hopped Beer Quality

Rutnik

Ocvirk

Košir

2022

Foods

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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.

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Section: Beer Bitternessmentioning

confidence: 64%

“…Linalool can arise from nerol or geraniol, and beta-citronellol can be produced from geraniol. Linalool could also be cyclised to alpha-terpineol [24]. Alpha-terpineol levels were far below the threshold values, so their contribution to aroma in our samples is negligible.…”

Section: Beer Aromamentioning

confidence: 74%

Impact of Hop Freshness on Dry Hopped Beer Quality

Rutnik

Ocvirk

Košir

2022

Foods

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“…This favours the presence of volatile compounds that are more representative of the essential oils originally present in hops [25][26][27][28][29][30]. Nevertheless, it is commonly accepted that the technique leads to greater extraction of polyphenols, which, in combination with iso-α-acids, results in a bitterness described as harsh and medicinal [31][32][33]. Finally, it should be considered that, in terms of water and raw material use, the dry hopping process is particularly costly since a considerable amount of beer is lost when the hops are removed [34].…”

Section: Introductionmentioning

confidence: 99%

Dip Hopping Technique and Yeast Biotransformations in Craft Beer Productions

Passaghe,

Tat,

Goi

et al. 2023

Fermentation

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This paper evaluates the effects of an alternative hopping technique, called dip hopping, on beer. This technique involves infusing hops in hot water (or in a portion of wort) and subsequently combining the infusion with the wort (after wort cooling) directly in the fermenter when the yeast is added for fermentation. The reference beers were produced employing the “traditional” late hopping technique, and the experimental beers were produced using the dip hopping technique. A variety of hops with a significant concentration of essential oil and a strain of yeast with high β-glucosidic activity capable of releasing aromatic molecules from precursors supplied by hops were used. The samples were analysed in terms of alcohol content, degree of attenuation, colour, and bitterness. Sensory analysis and gas chromatography analysis were also performed. The data showed statistically significant differences between the reference beers and the experimental beers, with the latter featuring greater hints of citrus, fruity, floral, and spicy aromas. As an overall effect, there was an increase in the olfactory and gustatory pleasantness of the beers produced with the dip hopping technique.

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“…The main purpose of bittering hopping is to achieve bitterness in beer. For this, hops have to be added at the beginning of the boil to allow sufficient time for isomerisation of the alpha-acids into iso-alpha-acids, which are the main source of bitterness in beers [6]. Another important reaction for alpha-acids is oxidation, which results in the generation of humulinones.…”

Section: Introductionmentioning

confidence: 99%

The Impact of Hop Freshness on Kettle-Hopped Beers

Rutnik,

Ocvirk,

Košir

2023

Foods

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Hops are an indispensable ingredient in beer, and the differences in their chemical composition impart the various tastes and aromas associated with different beers. However, during storage, hops undergo changes in their chemical composition. Here, the changes in aroma and bitterness of kettle-hopped beers were evaluated in an experiment conducted on three different hop varieties (Aurora, Celeia and Styrian Wolf) with five different hop storage index (HSI) values (0.3–0.7). Hops were added to boiling wort for 5, 45 and 90 min. Alpha-acids, iso-alpha-acids, humulinones, bitterness units and hop aroma compounds in the samples were chemically analysed. All samples also underwent sensorial analysis. The old hops were not problematic in terms of bitterness or early hopping time. However, later additions of old hops reduced the quality and intensity of the hop aroma. The limit value for use without negative consequences for kettle hopping was set at HSI 0.5 for Aurora and Celeia and HSI 0.6 for Styrian Wolf.

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Dynamics of Isomerization of Hop Alpha-Acids and Transition of Hop Essential Oil Components in Beer

Cited by 5 publications

References 21 publications

Impact of Hop Freshness on Dry Hopped Beer Quality

Impact of Hop Freshness on Dry Hopped Beer Quality

Dip Hopping Technique and Yeast Biotransformations in Craft Beer Productions

The Impact of Hop Freshness on Kettle-Hopped Beers

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