Changes in beer bitterness level during the beer production process

Beer has been enjoyed by consumers for years. Today, hops are inextricably associated with this beverage. Although they have been the subject of research for decades, knowledge of their bittering components and interactions during the beer production process is still incomplete. Current literature clearly indicates that the bitterness experienced in beer comes from a much wider range of compounds than just iso-α-acids. Although compounds that can be classified into β-acids, humulinones, hulupones, hard resins, and polyphenols are characterized by lower levels of bitterness and are present in hops in lower quantities than α-acids, they might determine, together with them, the final level of bitterness in beer. Unlike α-acids, the influence of compounds from these groups, their transformations, changes in their content during the beer production process and factors that affect their final concentration in beer have not yet been thoroughly studied. In case of α-acids, it is known that factors, such as chemical composition of wort, its extract and pH, amount of hops added and α-acids’ content, boiling time, and temperature at which hops were added influence the level of bitterness. This phenomenon is further complicated when dry hopping is used. Due to the presence of humulinones, polyphenols, and α-acids, a relatively simple spectrophotometric determination of IBU can give erroneous results. IBU determination, especially in dry-hopped beers, should be coupled with HPLC analysis, taking into account appropriate bitterness coefficients.

Impact of Hop Freshness on Dry Hopped Beer Quality

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.

Hop: An Emerging Crop in Subtropical Areas in Brazil

Brazil is one of the three largest beer producers in the world. Four basic ingredients are needed as raw material for the production of beer: water, malt, yeast, and hops (Humulus lupulus L.). Until recently, almost all of the hops in Brazil were imported from other countries. However, in the last decade, hop cultivation in Brazil has emerged due to the increase in the number of new craft breweries, which have demanded diversified raw material for the production of various types of beer. Hops is considered a short-day, temperate species, so the major challenge for the development of hop cultivation in Brazil, with high-yield capacity and with local typicity of bitterness and aroma, is the adaptation of cultivars to the photoperiod conditions in subtropical regions. This review addresses the history of hop cultivation in Brazil and characterizes the main climatic elements of three emerging subtropical growing regions located at different latitudes, such as air temperature, photoperiod, solar radiation, and water availability, to provide support for the development of new technologies for hop cultivation, including supplemental lighting, irrigation, and mulching.

Improving Effects of Hop-Derived Bitter Acids in Beer on Cognitive Functions: A New Strategy for Vagus Nerve Stimulation

Dementia and cognitive decline are global public health problems. Moderate consumption of alcoholic beverages reduces the risk of dementia and cognitive decline. For instance, resveratrol, a polyphenolic compound found in red wine, has been well studied and reported to prevent dementia and cognitive decline. However, the effects of specific beer constituents on cognitive function have not been investigated in as much detail. In the present review, we discuss the latest reports on the effects and underlying mechanisms of hop-derived bitter acids found in beer. Iso-α-acids (IAAs), the main bitter components of beer, enhance hippocampus-dependent memory and prefrontal cortex-associated cognitive function via dopamine neurotransmission activation. Matured hop bitter acids (MHBAs), oxidized components with β-carbonyl moieties derived from aged hops, also enhance memory functions via norepinephrine neurotransmission-mediated mechanisms. Furthermore, the effects of both IAAs and MHBAs are attenuated by vagotomy, suggesting that these bitter acids enhance cognitive function via vagus nerve stimulation. Moreover, supplementation with IAAs attenuates neuroinflammation and cognitive impairments in various rodent models of neurodegeneration including Alzheimer's disease. Daily supplementation with hop-derived bitter acids (e.g., 35 mg/day of MHBAs) may be a safe and effective strategy to stimulate the vagus nerve and thus enhance cognitive function.

Role of Characteristic Components of Humulus lupulus in Promoting Human Health

Over the next 50 years, the prevention and control of chronic diseases, such as obesity, cardiovascular disease, Alzheimer's disease, and many cancers, will be one of the most critical challenges in human health. Plant biochemistry and phytonutrient supplements are a promising complementary therapy for the management of chronic disease. Among them, Humulus lupulus has attracted special attention throughout the world because it contains numerous dietary phytochemicals that not only contribute to the aroma and flavor of beer but may also be used for medicinal purposes, as its properties include antiseptic, (an)aphrodisiac, anticancer, antiplatelet, antibacterial, antidiuretic, anti-inflammatory, sedative, hypnotic, and stomachic properties. This review sought to identify and understand the risk factors for chronic disease with a focus on two types of phytochemicals, bitter acids and xanthohumol. The goal was to understand how their metabolites promote human health and reduce the risk of chronic disease.

Modeling of α-acids and xanthohumol extraction in dry-hopped beers

The practice of dry-hopping has been used by the brewing industry to obtain beers with increased contents of flavor and bitterness compounds. Notwithstanding this, other compounds such as α-acids (AA) and xhanthohumol (XN) are co-extracted influencing the final characteristics of the beer, particularly its beneficial bioactivity. In this context a model for the understanding of AA and XN extraction by dry-hopping is proposed. The varieties Chinook (CHI), East Kent Goldings (EKG) and Tettnanger (TET) were assayed and robust statistical approaches were applied for data interpretation. Concentration of AA in beers post-maturation reached values higher than 20 mg/L using 2.8 g/L of CHI hops and 10 days of maturation. For XN, a similar behavior was verified. The maximum efficiency of AA and XN extraction (transfer rate) were reached at 13.5 days with dose rates of 147 and 13.9 mg/L, respectively.

Chemical Characterization of Beer Aging Products Derived from Hard Resin Components in Hops (Humulus lupulus L.)

The bitter taste of beer originates from resins in hops (Humulus lupulus L.), which are classified into two subtypes (soft and hard). Whereas the nature and reactivity of soft-resin-derived compounds, such as α-, β-, and iso-α-acids, are well studied, there is only a little information on the compounds in hard resin. For this work, hard resin was prepared from stored hops and investigated for its compositional changes in an experimental model of beer aging. The hard resin contained a series of α-acid oxides. Among them, 4'-hydroxyallohumulinones were unstable under beer storage conditions, and their transformation induced primary compositional changes of the hard resin during beer aging. The chemical structures of the products, including novel polycyclic compounds scorpiohumulinols A and B and dicyclohumulinols A and B, were determined by HRMS and NMR analyses. These compounds were proposed to be produced via proton-catalyzed cyclization reactions of 4'-hydroxyallohumulinones. Furthermore, they were more stable than their precursor 4'-hydroxyallohumulinones during prolonged storage periods.