The moisture content (MC) and acidity content (AC) of the fermented grains used in liquor production directly affect the liquor quality and yield; as such, they are important indicators used to evaluate the quality of fermented grains. In this study, extreme gradient enhancement algorithm (XGBoost), partial least square regression (PLSR), and extreme learning machine (ELM) models were developed based on spectral data collected by near-infrared (NIR) hyperspectral imaging (HSI) technology. First, PLSR models were established after SNV and MSC algorithms preprocessed the HSI data, and the best preprocessing method was determined (MC: SNV; AC: MSC). Then, the competitive adaptive reweighting sampling (CARS) algorithm and principal component analysis (PCA), both combined with the successive projection algorithm (SPA), were used to extract the characteristic wavelengths from the full-band spectral data. Ultimately, the XGBoost model developed using the characteristic wavelengths extracted by CARS-SPA most accurately predicted the MC (RPD = 6.4167, RP 2 = 0.9757, RMSEP = 0.0442 g·100 g−1) and AC (RPD = 13.0308, RP 2 = 0.9941, RMSEP = 0.0216 mmol·10 g−1). The results showed that the XGBoost model could more accurately predict the MC and AC of the fermented grains from hyperspectral images of the grains, providing an effective method for the rapid analysis of raw materials used in the fermentation of liquor.

Sauce-flavor baijiu products produced in different regions have perceptible differences in flavor characteristics, but the reasons for the formation of regional flavor substances are still unclear. The brewing process of sauce-flavor baijiu includes multiple rounds of pit fermentation. The base baijiu produced at the end of pit fermentation contributes significantly to the flavor of sauce-flavor baijiu products. This study investigated the microbial community succession and changes in flavor compounds during 7th round pit fermentation of sauce-flavor baijiu produced in Beijing region and comparatively analyzed the componential differences in microbial community and flavor compounds with sauce-flavor baijiu produced in other regions. It was found that Lactobacillus, Virgibacillus, Thauera, and Kroppenstedtia were the dominant bacterial genera, and Byssochlamys, Cutaneotrichosporon, and Apiotrichum were the dominant fungal genera. A total of 47 volatile compounds were identified and quantified in fermented grains. The concentrations of ethyl L(-)-lactate, ethyl caproate, and diethyl succinate gradually decreased with time, while the concentrations of phenethyl acetate, ethyl palmitate, and ethyl phenylacetate increased. The relative abundance of dominant microorganisms as well as the concentrations of volatile compounds showed a successional pattern with fermentation time. Lactobacillus, Virgibacillus, and Kroppenstedtia were positively associated with the synthesis of ethyl phenylacetate and phenylethyl alcohol, while negatively associated with the synthesis of ethyl caproate. Differences in microbial community structure are partly responsible for the regional flavor characteristics of sauce-flavor baijiu and the flavor differences between rounds of base baijiu. This study will provide in-depth insights into the formation of regional flavor compounds of sauce-flavor baijiu.

The infestation of brewing grains with filamentous fungi can have wide-ranging effects, including poor processability during malting and brewing, diminished storage quality, and potential threats to food safety and human health. Darkly pigmented fungi, also known as dematiaceous fungi, that spoil cereal grains during ripening and storage comprise a rich source of extracellular enzymes, including various cellulolytic enzymes and other polysaccharide-degrading enzymes, along with proteolytic enzymes, that can modify the physicochemical properties of cereal grains, contribute to substrate hydrolysis during germination, and may have a negative influence on malting and brewing properties. This review article addresses the potential impact of dark-pigmented fungi on malting and brewing quality beyond food safety. It summarizes the current knowledge on secreted fungal hydrolytic enzymes involved in barley grain degradation and discusses their potential impact in terms of malting and brewing quality, focusing on dematiaceous fungi and those causing black symptomatology on the grain. Overall, this review highlights the necessity for further research into the impact of dark-pigmented fungi on malting and brewing quality.

This article presents a background on hop chemistry, methods of addition during the brewing process to provide aroma and bitterness, and it discusses the optimal conditions for dry-hopping to maximize aroma extraction while minimizing bitterness and other issues. Essential oil extraction occurs much faster than what is commonly believed by brewers, reaching a maximum within only 2–3 days, and it is not negatively impacted by lower temperatures. This review discusses the potential problems of refermentation that may occur in packaged dry-hopped beers from the degradation of unfermentable carbohydrates by hop dextrinases, and the limits of the IBU scale in dry-hopped or sour beers to correlate perceived bitterness with iso-α-acids levels. While hop varieties can vary in bitter acids and essential oil levels and composition, the aroma of raw hops may not correlate well with the ‘hoppy aroma’ of the final product due to biotransformation of geraniol and enzymatic release of geranyl esters and polyfunctional thiols by brewing yeast. Timing of addition, temperature, alcohol levels, agitation, yeast strain, and even fermentation vessel dimensions are all factors that can influence the extraction, transformation, haze formation or loss of volatiles by the scrubbing effect of carbon dioxide and adsorption to yeast cells. Finally, the newest products available for brewers are presented, from new hop products to genetically-modified yeasts with enhanced thiol cleavage ability, to potential plant alternatives to hops. A link is provided in the ‘Background Section’ of the paper that takes the reader to the full paper and list of detailed references.

Recent industry roadmaps such as Crops 2030 and the Irish Whiskey Association’s Sustainability Roadmap 2022 emphasize the importance of increasing the use of Irish-grown grain in brewing and distilling. With the growth of the Irish distilling sector, there is a corresponding demand for raw materials and locally sourced grains. In Ireland, approximately 500 hectares of rye are harvested annually, with rye containing a similar range of starch as wheat. However, because rye contains more hemicelluloses and pentosans than other cereals, and because water-soluble pentosans tend to form viscous solutions in concentrated flour-water slurries, it is not widely utilised as a fermentation substrate. The purpose of this study is to examine pre-treatment with β-glucanase to enhance the alcohol output from rye flour. The research determined a baseline alcohol production of 187.1 LA/tonne dwb without the addition of β-glucanase. Using four predictor variables, response surface techniques were used to investigate the influence of β-glucanase on alcohol yield. A Box-Bekhan design was used to investigate time, temperature, calcium ions, and β-glucanase. When β-glucanase was administered at a dose rate of 3 U/g with the addition of 200 mg/L calcium ions and run at 50 °C for 30 min, the response surface approach yielded the highest alcohol output of 406 LA/tonne dwb. While, this yield is consistent with previous authors’ findings; it is lower than average yields for malted barley, wheat, and maize.

This work studies the fermentation kinetics to produce mead using Saccharomyces cerevisiae, selected from three commercial yeasts to generate a product with better organoleptic characteristics and greater acceptance by a group of untrained tasters. The values of the kinetic parameters of the fermentation were obtained from a series of fermentations at laboratory scale, maintaining constant the initial concentration of biomass (1.5 g/L), the operating temperature (33 °C) and the pH (4) and varying the initial soluble solids concentration in four values (10, 16, 22 and 25 °Brix). Based on the experimental results, a mathematical modeling was developed to estimate the variables of interest. Thus, from the application of the Monod model, the saturation constant (Ks) of 336.6 g/L was obtained, with a maximum specific growth rate () of 0.071 h−1. Using the integrated logistic model, the experimental values were adjusted to obtain the average value of of 0.0815 h−1. Finally, the maximum ethanol production rate (rpm) of 0.2621 g/L was obtained through the modified Gompertz model. Therefore, Monod, integrated logistic and modified Gompertz models were ideal mathematical tools to interpret the kinetic behavior of honey fermentations, predict and control this process, both on a laboratory scale and on a subsequent industrial scale. Thus, contributing to the knowledge of the dynamic behavior of mead production and its level of technological development.

Quantification of beer color of craft unfiltered, hazy, seltzer, and fruited beer styles can be problematic due to turbidity and unconventional ingredients. A novel integrating cavity spectrometer (ICS), designed to eliminate the effect of light scatter by the sample was employed to determine if it was able to more accurately quantify beer color compared to a conventional scanning spectrophotometer (CSS). A CSS was employed to measure the absorbance and transmission of 15 filtered and unfiltered craft brewery beer samples to determine the SRM color value and tristimulus color values. The ICS measures absorbance with a 430 nm LED to determine the single-point SRM value for each beer. The SRM values of unfiltered or 0.2 µm filtered beer samples were compared using Bland-Altman analysis and regression fits. Filtered and very clear beers showed strong agreement between the methods and Bland-Altman analysis confirmed their equivalence, particularly for SRM <25. Using the ICS alone, filtered beer versus unfiltered beer showed highly correlated values and narrow limits of agreement, successfully negating the effects of turbidity. In conclusion, SRM determination by ICS is equivalent to standard spectrophotometer single-point methods and superior in accurately determining the SRM color of hazy beers without filtration or centrifugation.

A headspace-proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF/MS) system that combines PTR-TOF/MS with a dynamic and reactive flavor-release monitoring system was constructed to measure the orthonasal aroma components in beer before and after foaming. Some aroma components in the headspace of beer after foaming in real time, such as m/z 145.1150 and m/z 173.1536, are thought to be derived mainly from ethyl hexanoate and ethyl octanoate, respectively, resulting in a fruity and sweet aroma. They showed significantly higher volatilizations than those in the headspace before foaming. The ratio of the concentration of headspace m/z of beer after foaming and before foaming showed a significant correlation with the partition coefficient of each assuming the main aroma component, indicating that the volatility of beer aroma with foaming depends on the hydrophobicity. The aroma components with high partition coefficients were believed to be able to associate with isohumulones and some proteins and to move to foam during foaming. They might be more volatilized by collapsing bubbles than those with low partition coefficients. Beer foam plays a novel role as a carrier of aroma, specifically promoting the release of some characteristic aroma compounds.

Lactic acid bacteria are key constituents in the souring process of traditional acidic beers, resulting from spontaneous or mixed fermentations. The development of such beer styles provides a balanced and complex-flavored beverage but is time-consuming and not easily repeatable. New time-efficient alternatives include successively pitching a souring bacteria and yeast, such that both have optimal fermentation conditions. In this study, each microorganism is assessed to comprehend its individual impact on the fermentation process (acidification and fermentation rates, attenuation, ethanol production) and its influence on physicochemical and organoleptic parameters. Lactic acid bacteria are responsible for the wort’s acidification, reaching a pH of 3.5 within 48 h, by converting up to 5 g/L of simple sugars into organic acids and other by-products. The two-step acidification and fermentation process alters the color and bitterness, the latter decreasing from an initial iso-α-acid concentration of 29 mg/L to an average of 13 mg/L. The sequential method shows that the decarboxylation and subsequent reduction of hydroxycinnamic acid precursors into their vinyl and ethyl derivatives is strain dependent. All tested lactic acid bacteria appear to possess the decarboxylation enzymes. However, only Lactiplantibacillus plantarum can reduce vinylphenols into ethylphenols.

Preliminary research was conducted on the analytical and flavor profiles of beers brewed (small-scale) with roasted specialty malts and raw malts as adjuncts. Beers were characterized by physico-chemical, sensory, and GC-MS analysis. From the beers produced, 79 volatile compounds were identified, and these were grouped into different categories. Alcohols and esters were found to be the most prevalent volatile compounds in the beers. Principal component analysis, as well as cluster analysis, was applied in order to investigate the similarities and distinctions between the various types of adjuncts and no adjunct beers. The volatile chemicals present in the beers showed that the nature and quantity of these compounds would have an effect on the flavor and quality of the beers. Beers prepared with the roasted wheat malt addition were characterized by the highest number of volatile compounds. Moreover, the beers with roasted wheat malt addition were characterized by higher bitterness (higher than the control beer), high antioxidant activity (equal to the control beer), and a high tannin content (but less than the control beer). Beers were evaluated by a sensory panel that concluded that the adjunct beers had a preferred flavor to the beers without adjunct addition. The highest-rated beer in the appearance, flavor, mouthfeel, and overall acceptability criteria was the adjunct beer with roasted wheat malt incorporated. This preliminary experimentation will help guide where future research is needed and where scale-up experiments with trained taste panels should focus.