Brief Insight into the Underestimated Role of Hop Amylases on Beer Aroma Profiles

Abstract

The current trend in craft breweries is to carry out heavy dry-hopping by increasing the hopping rate. This practice sometimes leads to uncontrolled and aberrant aroma profile production. The aim of this work was to determine whether part of the enzymatic content of hop (α-amylase and β-amylase) could impact yeast metabolism, resulting in aroma profile modification during secondary fermentation. In this research, spectrophotometric methods were used to assess the amylase activity within hop. Moreover, liquid chromatographic methods (HPLC-ELSD) showed modification of the beer sugar profile by production of glucose and maltose as well as by the degradation of a higher degree of polymerization sugar by hop enzymes. Furthermore, gas chromatographic techniques (GC-ECD/FID) were used to assess yeast metabolism using vicinal diketones (diacetyl/ pentanedione) as a marker of the secondary fermentation. Finally, a principal component analysis (PCA) of the yeast main aromas (esters, higher alcohols, and aldehydes) demonstrated the significance of this yeast-hop interaction on the beer's aroma profile.

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

“…This may be due to higher concentrations of amylolytic enzymes in the beer environment. This was partly confirmed by Werrie et al [ 111 ]. They stated that this is only true when there are no live yeast cells in the beer environment.…”

“…In addition, in the worst cases, beer with this defect can pose a health risk to consumers, as too-high pressure in the bottle can cause it to explode. Beer with hop creep may also require longer maturation times as a result of the prolonged fermentation and possible production of vicinal diketones (diacetyl and pentanedione) [ 111 ]. It is known that the amylolytic enzymes present in hops are responsible for this phenomenon.…”

“…Based on current knowledge, such an approach will also prevent the biotransformation of hop compounds. Therefore, it seems most appropriate to design a beer by taking into account the possible refermentation processes due to dry-hopping [1,85,103,[111][112][113][114][115]118,119].…”

Aroma Profiles of Dry-Hopped Ciders Produced with Citra, Galaxy, and Mosaic Hops

“…Quantitative analysis of triplicate Gravenstein apple cider fermentations has revealed a large array of VOCs. The 89 total VOCs detected by HS-SPME-GC-MS throughout fermentation and dry hopping included higher alcohols (11), acetate esters (7), ethyl esters (10), other esters (32), aldehydes (5), ketones (8), volatile acids (5), and terpenes (11). Specifically, species above the published perception thresholds were monitored carefully, revealing three unique ciders with appealing citrus (Citra hops), fruity (Galaxy hops), and floral (Mosaic hops) aromas.…”

“…The story is not quite this simple, however. The VOCs that dominate the headspace of hops are often quite different from those in the headspace of dry-hopped beer, due to biotransformation and other variables involved in the fermentation process [9,10]. For this reason, it is important to monitor the aroma development after dry hopping, to differentiate which aroma active compounds were efficiently extracted from the hops into the beverage, and how they may have changed.…”