New insights into the characteristic flavor components of traditional sour beers such as Lambic and Flanders Red Ale beers

In recent years, the demand for beers with a variety of flavors has increased considerably owing to the diversification of consumer preferences. Sour beer is characterized by a sour taste unlike normal beer flavor, and previous studies on sour beer have been primarily focused on addressing issues, such as inconsistent product quality and long production time, and on the associated microorganisms. Scientific knowledge regarding the characteristic flavor of sour beer and flavor components is limited. Therefore, in this study, we aimed to clarify the characteristic sensory attributes of sour beer and the component profiles that explain these attributes. Component analysis was performed on 10 traditional sour beers (eight Flanders Red Ales and two Lambics), using untargeted gas chromatography-mass spectrometry with liquid-liquid extraction, liquid chromatography-mass spectrometry targeting amines and anionic compounds. Further, sensory evaluation was conducted by well-trained panelists via quantitative descriptive analysis. Orthogonal partial least squares regression analysis was also conducted to investigate candidate flavor components. Thus, 261 components were identified and our methods could explain the flavor attributes of the examined samples. Comprehensive component profiling data also showed that differences in fermentation method, barrel aging duration, and blending ratio affected beer flavor. Further, Lambics were found to be characterized by citrus and phenolic aroma, while Flanders Red Ales were characterized by solvent-like aroma, sourness complexity, full bodied, graininess, astringency, and bitterness. These findings may serve as a basis for addressing issues related to sour beer production and may facilitate process design for obtaining targeted sour beer flavors.

Biocompatibility in Ternary Fermentations With Lachancea thermotolerans, Other Non-Saccharomyces and Saccharomyces cerevisiae to Control pH and Improve the Sensory Profile of Wines From Warm Areas

Global warming is causing serious problems, especially, in warm regions, where musts with excess sugars and high pH produce wines with decreased freshness and unstable evolution. This study aimed to determine biocompatibility between yeast species, the capacity for microbiological acidification, and the aromatic profile produced in ternary fermentations in which Lachancea thermotolerans has been co-inoculated with Hanseniaspora vineae, Torulaspora delbrueckii, or Metschnikowia pulcherrima, and the fermentation process is subsequently completed with sequential inoculation of Saccharomyces cerevisiae. For this purpose, different cell culture media and instruments were used such as infrared spectroscopy, enzymatic autoanalyzer, chromatograph coupled with a flame ionization detector, spectrophotometric analysis, among others. The behavior of these yeasts was evaluated alone and in co-inoculation, always finishing the fermentation with sequential inoculation of S. cerevisiae, at a stable temperature of 16°C and with a low level of sulfites (25 mg/L) in white must. Significant results were obtained in terms of biocompatibility using population counts (CFU/ml) in differential plating media that permitted monitoring. Quantification of the five species was studied. Concerning acidification by L. thermotolerans in co-inoculations, we showed some metabolic interactions, such as the inhibition of acidification when H. vineae/L. thermotolerans were used, generating just over 0.13 g/L of lactic acid and, conversely, a synergistic effect when M. pulcherrima/L. thermotolerans were used, achieving 3.2 g/L of lactic acid and a reduction in pH of up to 0.33. A diminution in alcohol content higher than 0.6% v/v was observed in co-inoculation with the L. thermotolerans/M. pulcherrima yeasts, with total sugar consumption and very slow completion of fermentation in the inoculations with H. vineae and T. delbrueckii. The aromatic composition of the wines obtained was analyzed and a sensory evaluation conducted, and it was found that both L. thermotolerans and co-inoculations retained more aromatic esters over time and had a lower evolution toward the yellow tones typical of oxidation and that the best sensory evaluation was that of the Lt + Mp co-inoculation. Lachancea thermotolerans and co-inoculations produced wines with low levels of volatile acidity (<0.4 g/L). This work shows that good consortia strategies with binary and ternary fermentations of yeast strains can be a powerful bio-tool for producing more complex wines.