Provocation: prolonged maturation of beer is of unproven benefit

Approaches to brewing are suffused with dogmatic insistence that certain techniques are unequivocally linked to the delivery of quality products. Amongst these belief sets is the perseverance with prolonged maturation (or ‘conditioning’) times post-fermentation. Historically the justification for these lagering techniques was to allow settling of solids, carbonation, flavour maturation and removal of chill haze entities. As science and technology have advanced it is unequivocally the case that solids and chill haze precursors can be dealt with in short order and without the need for lengthy treatments.  Equally it is perfectly possible to deliver specified levels of carbonation without the need for all the carbon dioxide to be introduced via yeast action. However, there remain many who feel that the nature of carbonation differs depending on which approach is taken. Herein lies one of the research areas that the author proposes. The perception of carbonation is not primarily due to bubble release on the palate, but rather is through the detection of carbonic acid. Is there a difference in the availability of this form of the gas depending on the mode of carbonation and to what extent does the adsorption of the carbonic acid on polypeptides in the beer have a role to play?  In terms of flavour, the advocates for lagering insist that there needs to be a handling of vicinal diketones, acetaldehyde, and hydrogen sulphide. However, all of these can be controlled through attention to primary fermentation. Then, the proponents for maturation insist that there is a desirable release of non-volatile materials into beer, which substances supposedly benefit the balance and mouthfeel of the lager. These include amino acids and nucleotides. It seems to this author however that the likeliest explanation for the greatly increased levels of these materials and of pH is autolysis of yeast. This, together with the disadvantageous impact of increased free amino nitrogen and higher pH on aspects such as biological stability, flavour stability and foam, should convince any brewer that there is a sound argument for avoiding the prolonged contact of beer with yeast. Indeed, a metabolomic approach to studying changes in non-volatile substances under conditions where there is little or no autolysis, revealed no detectable changes in any entity.  The author is open to being convinced that there are yet unidentified materials that are developed (whether through the action of viable yeast or by yeast autolysis) as beer is stored, substances which can be proven through sound organoleptic investigation to benefit the flavour of beer. Perhaps the Japanese term kokumi is what we are looking for here: ‘rich taste’. This is believed to be afforded by γ-glutamyl peptides and, inter alia, these are to be found in yeast extracts. Herein lies the second experimental approach that the author recommends for pursuit. 

Effects of Production Methods on Flavour Characteristics of Nonalcoholic Wine

The growing awareness on the negative effects of alcohol on health and other factors like religious beliefs, responsible driving, and strict alcohol regulatory laws have contributed to the overwhelming demand for nonalcoholic wines. Numerous methods are available for producing nonalcoholic wines which encompass both restrictive ethanol production processes (interrupted fermentation, cold fermentation, juice/wine blends, use of unripe fruit, enzyme, and special and immobilized yeasts) and alcohol removal methods (heat, membrane, and extraction techniques). Studies have shown that these methods significantly affect the flavour characteristics of the wine, which is a key quality parameter in wine purchasing and consumption. It is in view of this that this work seeks to review current articles on the effects of production methods on the flavour characteristics of nonalcoholic wine. This review will provide insight on nonalcoholic wine production methods, their merits and demerits, and contributions to flavour characteristics. It will also unfold research opportunities in the field of nonalcoholic wine production for continual improvement and development of the wine industry.

Higher NADH Availability of Lager Yeast Increases the Flavor Stability of Beer

Flavor stability is a significant concern to brewers as the staling compounds impart unpleasant flavor to beer. Thus, yeasts with antistaling ability have been engineered to produce beer with improved flavor stability. Here, we proposed that increasing the NADH availability of yeast could improve the flavor stability of beer. By engineering endogenous pathways, we obtained an array of yeast strains with a higher reducing activity. Then, we carried out beer fermentation with these strains and found that the antistaling capacities of the beer samples were improved. For a better understanding of the underlying mechanism, we compared the flavor profiles of these strains. The production of staling components was significantly decreased, whereas the content of antistaling components, such as SO₂, was increased, in line with the increased antistaling ability. The other aroma components were marginally changed, indicating that this concept was useful for improving the antistaling stability without changing the flavor of beer.