Humulus lupulus- a story that begs to be told. A review

Abstract

The hop cones of the female plant of the common hop species Humulus lupulus L. are grown almost exclusively for the brewing industry. Only the cones of the female plants are able to secrete the fine yellow resinous powder (i.e. lupulin glands). It is in these lupulin glands that the main brewing principles of hops, the resins and essential oils, are synthesized and accumulated. Hops are of interest to the brewer since they impart the typical bitter taste and aroma to beer and are responsible for the perceived hop character. In addition to the comfortable bitterness and the refreshing hoppy aroma delivered by hops, the hop acids also contribute to the overall microbial stability of beer. Another benefit of the hop resins is that they help enhance and stabilize beer foam and promote foam lacing. In an attempt to understand these contributions, the very complex nature of the chemical composition of hops is reviewed. First, a general overview of the hop chemistry and nomenclature is presented. Then, the different hop resins found in the lupulin glands of the hop cones are discussed in detail. The major hop bitter acids (α-and β-acids) and the latest findings on the absolute configuration of the cis and trans iso-α-acids are discussed. Special attention is given to the hard resins; the known δ-resin is reviewed and the ε-resin is introduced. Recent data on the bittering potential and the antimicrobial properties of both hard resin fractions are disclosed. Attention is also given to the numerous essential oil constituents as well as their contributions to beer aroma. In addition to the aroma contribution of the well-known essential oil compounds, a number of recently identified sulfur compounds and their impact on beer aroma are reviewed. The hop polyphenols and their potential health benefits are also addressed. Subsequently, the importance of hops in brewing is examined and the contributions of hops to beer quality are explained. Finally, the beer and hop market of the last century, as well as the new trends in brewing, are discussed in detail. Hop research is an ever growing field of central importance to the brewing industry, even in areas that are not traditionally associated with hops and brewing. This article attempts to give a general overview of the different areas of hop research while assessing the latest advances in hop science and their impact on brewing.

Beer metabolomics: molecular details of the brewing process and the differential effects of late and dry hopping on yeast purine metabolism

“…Ferulate has been characterized in hop extracts ; however, analysis of the aqueous fraction of hop extracts in this study revealed no measurable ferulate (data not shown) at the micromolar detection limit of NMR. Myrcene is one of most abundant molecules found in hop oil and was the only hop aroma compound that was able to be identified in this work. Myrcene was recently reported to be present at 3 μM in beer , which is at the detection limit of our technique.…”

Brewing Trials of Barley Varieties Registered in the Czech Republic

“…Trpkost piv nepřímo úměrně korelovala pouze s rozdílem mezi zdánlivým a dosažitelným prokvašením (r = -0,417) a koncentrací původní mladiny (r = -0,498), vyšší koncentrace extraktu, nižší prokvašení pravděpodobně snižuje trpkou chuť. Trpkost chuti piva je přisuzována některým polyfenolovým látkám sladu (Narziss 1992(Narziss , 1995, chmele (Almaguer et al, 2014) a alkaloidům hordatinům, pocházejícím ze sladu (Kageyama et al, 2011).…”

“…Higher concentration of extract and lower attenuation probably reduce astringency. The astringency of beer is attributed to certain polyphenol substances from malt (Narziss 1992(Narziss , 1995, hops (Almaguer et al, 2014) and the alkaloids hordatins derived from malt (Kageyama et al, 2011).…”

Technological influence on sensory stability and antioxidant activity of beers measured by ORAC and FRAP

“…The phenolic content of malted barley depends on the malting regime, with higher levels of malt modification resulting in a higher content of free phenolic acids . There is a myriad of antioxidant compounds derived from hops ( Humulus lupulus L.): Resinous compounds like α ‐acids or prenylated chalcones and non‐resin phenolic compounds like phenolic acids or flavonoids . Hop is either added at the beginning of wort boiling to achieve the desired bitterness or at the end of boiling or during whirlpool rest to impart a hoppy aroma to the final beer .…”