The biotransformation and release of polyfunctional thiols (PFTs), including 3-sulfanylhexan-1-ol (3SH), 4-methyl-4-sulfanylpentan-2-one (4MSP), and 3-sulfanyl-4-methylpentan-1-ol (3S4MP), contribute to tropical fruit aromas in beer. This study examines the effect of fermentation temperature (15–30 °C) on PFT production across five commercial yeast strains. Pilot-scale beers were brewed with Cascade hops and analyzed for 29 aroma compounds. A strong temperature-dependent increase in 3SH (33–72%) was observed, with the lager yeast strain yielding the highest levels at the high-temperature condition (30 °C). However, sensory analysis indicated that elevated thiol concentrations alone did not enhance tropical aroma. Instead, increased levels of β-ionone, β-damascenone, acetate esters, and terpenoids at higher fermentation temperatures correlated with a more pronounced tropical character, particularly with the ale yeasts. These results highlight the intricate relationships between thiol levels and concurrent volatile compounds, emphasizing that elevated thiol presence alone does not directly translate to heightened tropical aromatic expression in beer.

When heat treating (pasteurizing) bottled or canned, carbonated beverages, such as beer and beer products or soft drinks, to reduce and/or kill any potential product spoilage organisms in their respective container, usually large tunnel pasteurizers are used. These machines spray hot water over the containers to ultimately reach a sufficient core temperature in the beverage container. Studies have shown that this process water contains a high count of diverse microorganisms. Reports from the industry and proven incidents imply that in very rare cases this process water and the related ingress of microorganisms can be detected in microbiological quality control of the product. To this date no investigations have proven or disproven these rare events. This study aims to collect evidence on the likelihood of these events occurring during large scale pasteurization. The possibility of an exchange with the environment during pasteurization could be proven by loss of CO2 throughout the process. This only occurred in bottles closed with crown corks, not in swing tops and cans. An ingress of process water could not be proven in the presented study but evidence was found that crown cork bottles are also the most likely container type for such a phenomenon to happen.

The binding and subsequent release of aldehydes from beers through aging is of central importance to beer flavor change through shelf-life. Here we report fundamental studies, targeted at improving understanding of the nature of aldehyde binding to, and release from, the beer matrix. Three commercial brands of lager beer, brewed using different adjunct grist bills, were selected for the study. Each was freeze-dried and reconstituted (30% w/w, freeze dried extract/ultra-pure water) to form a concentrated solution of “beer matrix.” With this solution, the affinity and type of interactions of the matrix toward selected aldehydes were investigated. In a series of “challenge” experiments, staling aldehydes were spiked into the concentrated beer matrices and headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC-MS) was used to determine percentage bound and percentage displacement of aldehydes measured in each case. A key finding was that each matrix displayed unique patterns of binding behavior toward the staling aldehydes. Furthermore, competitive binding was clearly observed whereby 3-methylbutanal generally showed the greatest binding on addition (and this was not impacted by the concentrations of other aldehydes present) as well as the ability to displace other aldehydes from the matrix. The full nature and range of the binding sites from which the aldehydes are being displaced remains unknown and further research is needed to better understand the complex equilibria involved in the multiple forms of binding which are envisaged to take place between aldehydes and the beer matrix.

The aroma of beer results from complex interactions between raw materials and microbial metabolism during brewing and fermentation processes. While the contributions of specialty malts and yeast to the beer aroma are well documented, their interplay—particularly with lager yeast strains—remains underexplored. Thus, this study investigates how four commercial Saccharomyces pastorianus strains impact the aroma of beers brewed with 100% Pilsner, 20% caramel, or 2% roasted barley malt. Pilot scale wort production and lab scale fermentation was conducted under standardized conditions. The aroma of the beers was assessed using a trained sensory panel and applying check-all-that-apply (CATA), complemented by headspace gas chromatography-mass spectrometry (HS-GC-MS) to determine volatile composition. Results revealed that both malt type and yeast strain significantly influenced beer aroma. Roasted malt exerted the most pronounced effect, but yeast strain-specific metabolic activities also distinctly modulated aroma outcomes, especially for attributes such as coffee and caramel. Analysis of volatiles confirmed strain-dependent biotransformation and selective retention of malt-derived precursors. Multiple factor analysis showed that in some cases, yeast strain had an equal or greater impact on aroma than malt type. This study challenges the view of lager yeasts as metabolically neutral and underscores the importance of strain selection for aroma optimization in lager-style beers.

Winter-type gushing refers to the spontaneous overflow of beer upon opening, due to rapid carbon dioxide release. While previous research has focused primarily on the roles of proteins and proteases in gushing, the impact of hops has not been studied extensively. In this study, the influence of malt and hops on winter-type gushing was investigated, with particular attention on the chemical components and mechanisms involved. Beers brewed with higher hopping rates exhibited significantly greater overfoaming, with malt playing an important role in inducing gushing. Fractionation of hop extract revealed that catechins are candidate compounds for promoting gushing. Chemical analyses demonstrated that catechins and procyanidins derived from hops increased the amount of overfoaming beer. Comparative analyses of polyphenols from malt and hops revealed that hop-derived catechins showed a higher gushing potential. Observations of chemical changes during storage suggest that the formation of oxidatively coupled multi-bridge oligomeric structures of catechin may contribute to gushing activity. The findings provide insights into the importance of malt- and hop-derived polyphenols in winter-type gushing and offer new insights into the underlying mechanisms.

Water chemistry is a critical factor in shaping the sensory characteristics and overall quality of kombucha, a fermented tea beverage celebrated for its unique flavor and health benefits. This review explores the relationship between water composition focusing on key ions, such as bicarbonate, sulfate, chloride, and the flavor profile of kombucha. Drawing parallels from studies on other fermented beverages, such as beer and wine, this article examines how water chemistry influences microbial activity, pH, tea polyphenol extraction, and sensory attributes. Moderate concentrations of some ions have been shown to enhance the extraction of bioactive tea compounds and contribute to desirable sensory attributes, such as balanced acidity and complex flavor profiles. Conversely, excessive levels of certain ions (such as bicarbonate and sulfate) can inhibit microbial activity, delay fermentation, and produce off-flavors. Despite these findings, there is a lack of sensory evaluation studies directly linking water ionic composition to flavor perception in kombucha. This review highlights mechanisms through which the mineral composition of water interacts with fermentation substrates and microbes to shape the final quality of the product. These interactions vary significantly across different fermented beverages, including beer, wine, and kombucha, emphasizing the need to tailor water profiles for specific fermentation outcomes. Understanding these effects is crucial for optimizing production processes and achieving desired sensory profiles.

Accurate detection of the key acid and ester components in the original distillate of strong-aroma Baijiu is crucial for Baijiu quality control and provides a scientific basis for blending and storage processes, traditional detection methods primarily rely on sensory evaluation combined with gas chromatography analysis. These methods are time-consuming and subject to operator bias. To address this, we propose a novel hybrid framework integrating Fourier transform infrared (FTIR) spectroscopy and machine learning for rapid detection. FTIR spectral of original distillate of strong-aroma Baijiu samples from different distillation periods were collected and preprocessed using Savitzky-Golay (S-G) smoothing, first-order derivative, and standard normal variate (SNV) transformation. Feature selection was carried out through the least absolute shrinkage and selection operator (LASSO) and competitive adaptive reweighted sampling (CARS). Following this, predictive models were constructed using partial least squares regression (PLSR), long short-term memory (LSTM) networks, and least squares boosting (LSBoost). The parameters of these models were optimized by the Grey Wolf Optimization (GWO) algorithm. The results show that the LASSO-GWO-LSTM model achieved the best performance in predicting the concentrations of ethyl acetate and lactic acid. For the ethyl acetate model, the root mean square error of prediction ( RMSE P ), R square of prediction ( R P 2 ), and relative percentage difference‌ of prediction ( RPD P ) reached 0.0967, 0.9949, and 14.6591, respectively. For the lactic acid prediction model, the corresponding values were 0.0152, 0.9805, and 7.0378. These results far exceed those of conventional PLSR models, indicating that the combination of FTIR and machine learning (LASSO-GWO-LSTM) is a promising method for real-time, high-precision, non-destructive analysis of acid and ester concentrations in the original distillate of strong-aroma Baijiu.

Traditionally, malted barley has served as the primary starch source for brewing, with other grains such as rice serving as adjuncts. However, barley’s susceptibility to climate trend-induced yield decrease raises concerns for the brewing industry’s future supply. In contrast, rice, known for its climate resilience and gluten-free characteristic, emerges as a promising alternative with good malting qualities. To further explore malted rice’s brewing potential, ten malted rice and one malted pale two-row barley were fermented with Saccharomycodes ludwigii to produce non-alcoholic beer (NAB) and low-alcoholic beers (LAB) (NABLAB, 0.26–0.84% alcohol by volume). The beers produced were measured for physicochemical parameters, volatiles, and sensorial attributes. Physicochemical parameters included alcohol content, density, and color. Volatiles were analyzed using headspace solid phase microextraction gas chromatography mass spectrometry (HS-SPME-GC-MS). Sensorial attributes were quantified using descriptive analysis with a trained panel. Results showed that most malted rice self-saccharified and produced worts with higher fermentability using S. ludwigii than malted barley. Malted non-aromatic non-pigmented rice LAB were sensorially similar to malted barley NAB. Malted aromatic rice and malted pigmented rice led to unique flavor profiles, signaling the potential of rice as a novel valuable ingredient in brewing. This study sheds light on rice’s suitability for brewing and underscores the potential of malted rice to diversify beer offerings while addressing long-term sustainability concerns regarding crop yield in the brewing industry.

Foam quality is one of the most critical attributes of beer, and foam color plays a key role in consumer perception and appeal. Despite its importance, there is currently no established method for objectively evaluating color of beer foam. This study employed a two-dimensional (2D) colorimeter capable of capturing the full spectrum of colors perceivable by the human eye to establish a novel method for evaluating the color and whiteness of beer foam. Using L*, a*, and b* values obtained from the 2D colorimeter, we established a quantitative method for evaluating foam appearance. Our results revealed a significant correlation between beer liquid color (°EBC) and foam whiteness. We also investigated the effects of beer aging on foam whiteness. These findings provide new insights into beer foam characterization and can contribute to enhancing the overall beer quality.

Foam is a crucial quality factor in beer, contributing to visual appeal, mouthfeel, aroma retention, and carbonation preservation. This study focuses on two phenomena characteristic of beer served using the dual-spout tap method common in Japan: “Frosty Mist (FM),” a layer of finely dispersed microfoam formed at the interface between beer liquid and foam layers, and “Foam Regenerative Ability (FRA),” the phenomenon of foam regeneration upon repeated tilting of the glass. A novel method was developed to quantify the total amount of FM through video analysis of the beer immediately after pouring. In addition, a dispensing apparatus was developed to measure FRA based on the increase in foam height after tilting and returning of the glass. Using five commercially available pilsner-style beers in Japan, we found significant differences in both FM and FRA among beer samples. A statistically significant positive correlation was also observed between FM and FRA, suggesting that FM may be a key factor contributing to foam regeneration. These foam evaluation methods could apply to dynamic analysis for the visual quality of foam in beer.