Aldehydes as Wort Off-Flavours in Alcohol-Free Beers—Origin and Control

Abstract

Although present in concentrations in microgrammes per litre level, aldehydes, in particular those derived from Strecker degradation, are known to majorly contribute to the undesired wort flavour of alcohol-free beers. In order to improve currently available products, one needs to understand the underlying cause for the over-prevalence and identify leverage points and methods to selectively reduce the aldehydes in alcohol-free beers. This work gives a short overview on relevant flavour-active wort flavours identified in alcohol-free beer and on their involved chemical formation pathways. Consequently, aldehyde removal technologies in general and in brewing industry are presented. Adsorptive removal of off-flavours by aldehydescavenging groups is already widely exploited in the packaging industry and may achieve reduction of these components to near depletion, depending on the process conditions. Its principles are adaptable to recovering off-flavours before filling. Also, supercritical CO 2 extraction has been successfully applied to separate flavours from food matrices. In brewing, the focus has been set to biologic conversion by restricted fermentation steps, but the reduction of key components of more than 70% is not achieved. Newer developments focus on thermal separation techniques that not only include non-specific physical dealcoholisation but also more selective technologies such as pervaporation, where aldehydes are reduced to near depletion. However, for most unit operations, selectivity and capacity are not yet investigated. Future research should explore the shortcomings of current techniques and overcome bottlenecks either by developing more specific methods for aldehyde removal and/ or a clever combination of unit operations to optimise the separation and process integration.

Understanding the sensory and physicochemical differences between commercially produced non-alcoholic lagers, and their influence on consumer liking

“…Samples 7 and 8, had cooked vegetable aroma, sour and bitter tastes, with previous studies finding similar results and correlating this to the presence of DMS ( Müller, Bellut, Tippmann, & Becker, 2017 ). Interestingly, it has been discussed that these ‘off-flavours’, as well as bitterness, become more dominant if other volatile compounds are removed to below threshold level, meaning the synergistic effects of the overall beer flavour become unbalanced ( Gernat et al, 2019 , Müller et al, 2017 ). This appears to be the case for these two samples, as they were only found to contain acetaldehyde in the lower boiling point volatile analysis.…”

“…Therefore, it seemed that this method removed a significant amount of volatiles, supporting previous literature which showed 76–97% of esters and 88–95% higher alcohols can be removed, due to similar boiling points to ethanol ( Montanari, Marconi, Mayer, & Fantozzi, 2009 ). Interestingly, samples produced by this method had increased levels of 2-furanmethanol, which is a compound that serves as a marker for the heat load impact on the beer; in this case showing a small, but indeed relevant, heat-induced off-flavour ( Gernat, Brouwer, & Ottens, 2019 ).…”

Characterizing Volatile and Nonvolatile Factors Influencing Flavor and American Consumer Preference toward Nonalcoholic Beer

“…However, these methods can generally result in NABs which are perceived to be too sweet because of their high residual extract and too worty because of the Strecker aldehydes extracted from the malt. 8 …”

Production and characterisation of non-alcoholic beer using special yeast

“…Diacetyl was detected only in our beer prepared with the control bottom fermenting brewer's yeast of S. pastorianus W96 and its level was above the minimum of the flavour threshold range (W96 -0.118 mg/l). A formation of aldehydes in beer involves different substrates and mechanism and occurs mainly during wort mashing and boiling (Gernat et al, 2019), but it is also affected by the storage temperature and dissolved oxygen presence (Soares da Costa et al, 2004). In this study, the concentration of benzeneacetaldehyde (green/ honey odour) ranged from 0.017 mg/l in the low-alcoholic beer fermented by hybrid yeast (HYB) to 0.058 mg/l in the non-alcoholic beer prepared with Sch.…”