Flavour instability of beer is a concern for brewers and has been investigated over many decades. Despite advancements in the characterisation of changes during the ageing process of pale lager beers (PLB), research on the flavour instability of non-alcoholic beer (NAB) - a beer style becoming increasingly prevalent on the market - is lacking. This study characterises the main chemical-analytical changes during a forced ageing process (90 days at 30°C) of seven commercially available NAB and compares the findings to the aged seven PLB counterparts. The major differences from ageing were increased concentrations of aldehydes and decreased levels of glutamine and esters, which occurred to the same extent for both beer styles. However, trans-iso-α-acids underwent a greater decrease in aged NAB, likely due to the lower pH of this style. Furthermore, correlations between ageing parameters in aged and fresh beers, previously found in PLB (Strecker aldehydes and corresponding amino acids, relative decrease of trans-iso-α-acids and pH) are confirmed and were also valid in NAB. Interestingly, sensory analysis revealed that aged NAB showed lower overall ageing scores, compared to aged PLB. This might be explained by differences in the formation of aldehydes causing worty off-flavours during ageing. In summary, this study provides a detailed overview of the ageing process of non-alcoholic beers in comparison with pale lager beers, which could help brewers to develop more flavour stable beers. © 2022 The Institute of Brewing & Distilling.

In this study, the major differences between commercial pale lager beers (PLB) and their non-alcoholic (NAB) counterparts were characterised by chemical-analytical and sensory analysis. Chemical-analytical profiling was performed using standard brewery analyses in addition to gas and liquid chromatography for quantifying volatile and non-volatile compounds. NAB differed in analytical composition from the PLB, in sugar, aroma, and amino acid profiles. Generally, the PLB contained higher levels of volatile aroma constituents (in particular, significantly higher levels of 2-methylbutan-1-ol, 3-methylbutan-1-ol, ethyl acetate, ethyl hexanoate and ethyl octanoate), specific amino acids (including cysteine, glutamine and alanine), sulphite, glycerol and proteins. NAB show significantly higher concentrations of fermentable sugars (maltose, glucose, fructose and maltotriose), as well as higher levels of amino acids (including threonine, serine and asparagine) and trans-2-nonenal. The PLB was similar in analytical composition, whereas the NAB could be discriminated into two clusters, reflecting different sugar profiles, reflecting the production technology. Organoleptic assessment described the flavour of the NAB as 'worty', 'sweet' and 'watery', while the PLB scored higher in 'bitterness intensity' and 'fullness'. Interestingly, those NAB where the analytical profile differed the most from their PLB counterparts exhibited the largest differences in sensory properties. Furthermore, this study suggests synergistic and/or antagonistic effects between groups of chemical compounds which may explain the flavour differences. For instance, high sugar levels suppress the perception of bitterness, whereas sugars, aldehydes and esters impact on the worty flavour of NAB. © 2021 The Institute of Brewing & Distilling