尽管世界啤酒产量每年在稳步增长,但酒花的产量却处于下降趋势,原因之一是科学技术的进步,提高了啤酒生产过程中α-酸转化成异α-酸的比率.尽管如此,关于啤酒中酒花香味成分演变的相关科学资料却非常稀少,啤酒里源自酒花的香味成分,或者更准备地说酒花中的易挥发性成分,受啤酒酿造过程的影响非常大.为了将独特的风味引入啤酒中,在酿造过程中仍需添加大量的酒花.为此,文章跟踪了采用干添加酒花法和非干添加酒花法两种方法酿制的单一酒花啤酒中酒花挥发性成分发生的变化.

To map the chemodiversity of key bitter compounds in hops, a total of 75 different samples collected from the global hop market were analyzed for 117 key bitter tastants by means of a multiparametric HPLC-MS/MSMRM method. Among the compounds detected, 2'',3''-epoxyxanthohumol was detected for the first time in hops and iso¬xantho¬humol M was identified as a marker compound for varieties grown in Germany. Hop ageing experiments in the absence and presence of air oxygen, respectively, were conducted to address the stability of hop-derived compounds during long-term storage.

Recent brewing trials indicated the occurrence of valuable bitter compounds in the hard resin fraction of hop. Aiming at the discovery of these compounds, hop's ε-resin was separated by means of a sensory guided fractionation approach and the key taste molecules were identified by means of UV/vis, LC-TOF-MS, and 1D/2D-NMR studies as well as synthetic experiments. Besides a series of literature known xanthohumol derivatives, multifidol glucosides, flavon-3-on glycosides, and p-coumaric acid esters, a total of 11 bitter tastants are reported for the first time, namely, 1",2"-dihydroxanthohumol F, 4'-hydroxytunicatachalcone, isoxantholupon, 1-methoxy-4-prenylphloroglucinol, dihydrocyclohumulohydrochinone, xanthohumols M, N, and P, and isoxanthohumols M, N, and P, respectively. Human sensory analysis revealed low bitter recognition threshold concentrations ranging from 5 (co-multifidol glucopyranoside) to 198 μmol/L (trans-p-coumaric acid ethyl ester) depending on their chemical structure. For the first time, LC-MS/MS quantitation of these taste compounds in Pilsner-type beer, followed by taste re-engineering experiments, revealed the additive contribution of iso-α-acids and the identified hard resin components to be truly necessary and sufficient for constructing the authentic bitter percept of beer. Finally, brewing trails using the ε-resin as the only hop source impressively demonstrated the possibility to produce beverages strongly enriched with prenylated hop flavonoids.

Two bottles of beer from an about 170-year-old shipwreck (M1 Fö 403.3) near the Åland Islands in the Baltic Sea were analyzed. Hop components and their degradation compounds showed that the bottles contained two different beers, one more strongly hopped than the other. The hops used contained higher levels of β-acids than modern varieties and were added before the worts were boiled, converting α-acids to iso-α-acids and β-acids to hulupones. High levels of organic acids, carbonyl compounds, and glucose indicated extensive bacterial and enzyme activity during aging. However, concentrations of yeast-derived flavor compounds were similar to those of modern beers, except that 3-methylbutyl acetate was unusually low in both beers and 2-phenylethanol and possibly 2-phenylethyl acetate were unusually high in one beer. Concentrations of phenolic compounds were similar to those in modern lagers and ales.

In this study, in vitro metabolism of hop-derived bitter acids was investigated. Besides their well-known use as bitter compounds in beer, in several studies, bioactive properties have been related to these types of molecules. However, scientific data on the absorption, distribution, metabolism, and excretion aspects of these compounds are limited. More specific, in this study, α-acids, β-acids, and iso-α-acids were incubated with rabbit microsomes, and fractions were subjected to LC-MS/MS analysis for identification of oxidative biotransformation products. Metabolism of β-acids was mainly characterized by conversion into hulupones and the formation of a series of tricyclic oxygenated products. The most important metabolites of α-acids were identified as humulinones and hulupones. Iso-α-acids were found to be primarly metabolized into cis- and trans-humulinic acids, next to oxidized alloiso-α-acids. Interestingly, the phase I metabolites were highly similar to the oxidative degradation products in beer. These findings show a first insight into the metabolites of hop-derived bitter acids and could have important practical implications in the bioavailability aspects of these compounds, following ingestion of hop-based food products and nutraceuticals.

Beer is one of the most consumed beverages in the world due to its alluring taste and aroma, and much effort has been made to reveal the structures responsible for the sensory sensation. However, the precise contribution of hop-derived volatiles towards the hoppy aroma of beer is far from being understood. For a long time, the aroma of fresh beer was believed to be mainly imparted by a few single compounds. Yet, studies revealed that sensorial perception of the hoppy aroma of beer is more complex than originally thought. Furthermore, the factors that are causing the individual varietal perceivable differences originating from distinct hop varieties used for late and dry hopping have not been revealed yet.To gain insights into the way hoppy aroma develops throughout beer manufacturing, one should first understand the impact of the different brewing process steps on the analytical composition of the volatile fraction of intermediate worts and final beers. Therefore, in this study, samples were taken at different stages along the brewing process of single hop beers and analyzed via headspace solid-phase microextraction and gas chromatography-mass spectrometry (HS-SPME GC-MS), thereby aiming at accurate determination of both the full spectrum of hop oil-derived constituents and of the higher esters and higher alcohols produced during fermentation. Our investigation pinpoints analytical changes in the volatile pattern of the wort and beer samples that are induced by the boiling and fermentation processes, as well as the applied late and additional dry hopping techniques.Concentrations of the "floral" (e.g. oxygenated fraction of total hop essential oil composed of monoterpene alcohols, esters, ketones and aldehydes) and the sesquiterpenoid hop oil fractions changed significantly along the brewing process. In contrast to that, concentrations of alcohols, ketones and esters in beers were found to be mainly influenced by the fermentation. Regardless of the hop variety used, early and late hopping clearly affected the absolute concentration of hop oil constituents. However, early and late hopping does not affect the original intrinsic qualitative composition of hop oil constituents. Furthermore, dry hopping significantly increases the level of hop essential oil constituents.

Dirk Naudts2, Denis De Keukeleire3, Guido Aerts1 and Luc De Cooman1 1 Flavour+ | Lab of Enzyme, Fermentation, and Brewing Technology (EFBT) | KU Leuven @ KAHOSL, Gent, Belgium; 2 De ’proef’brouwerij | R&D Department | Lochristi, Belgium; 3 Em. Professor | UGent, Gent, Belgium From Wort to Beer: The Evolution of Hoppy Aroma of Single Hop Beers produced by Early Kettle Hopping, Late Kettle Hopping and Dry Hopping

Beer, one of the most consumed beverages worldwide, has been shown to stimulate gastric acid secretion. Although organic acids, formed by fermentation of glucose, are known to be stimulants of gastric acid secretion, very little is known about the effects of different types of beer or the active constituents thereof. In the present study, we compared the effects of different beers on mechanisms of gastric acid secretion. To investigate compound-specific effects on mechanisms of gastric acid secretion, organic acids and bitter compounds were quantified by HPLC-DAD and UPLC-MS/MS and tested in human gastric cancer cells (HGT-1) by means of a pH-sensitive fluorescent dye which determines the intracellular pH as an indicator of proton secretion. The expression of relevant genes, coding the H+/K+-ATPase, ATP4A, the histamine receptor, HRH2, the acetylcholine receptor, CHRM3, and the somatostatin receptor, SSTR2, was determined by qPCR. Ethanol and the organic acids succinic acid, malic acid, and citric acid were demonstrated to contribute to some extent to the effect of beer. The bitter acids comprising α-, β-, and iso-α-acids were identified as potential key components promoting gastric acid secretion and up-regulation of CHRM3 gene expression by a maximum factor of 2.01 compared to that of untreated control cells with a correlation to their respective bitterness.

Dirk Naudts2, Denis De Keukeleire3, Guido Aerts1 and Luc De Cooman1 1 Flavour+ | Lab of Enzyme, Fermentation, and Brewing Technology (EFBT) | KU Leuven @ KAHOSL, Gent, Belgium; 2 De ’proef’brouwerij | R&D Department | Lochristi, Belgium; 3 Em. Professor | UGent, Gent, Belgium From Wort to Beer: The Evolution of Hoppy Aroma of Single Hop Beers produced by Early Kettle Hopping, Late Kettle Hopping and Dry Hopping