A Comprehensive Evaluation of Flavor Instability of Beer (Part 2): The Influence of De Novo Formation of Aging Aldehydes

Abstract

Flavor instability of beer is affected by the rise of aroma-active aldehydes during aging. Aldehydes can be either released from bound-state forms or formed de novo. This second part of our study focused on the de novo formation of aldehydes during the Maillard reaction, Strecker degradation, and oxidation reactions. Key precursor compounds for de novo pathways are free amino acids. This study varied the potential for reactions by varying free amino acid content in fresh beer using different proteolytic malt modification levels (569–731 mg/100 g d. m. of soluble nitrogen) of the used malt in brewing trials. Overall, six pale lager beers were produced from three malts (different malt modification levels), each was made from two different barley varieties and was naturally and forcibly aged. It was found that higher malt modification levels in fresh beer and during beer aging increased amino acid and dicarbonyl concentrations as aging precursors and Strecker aldehyde contents as aging indicators. Dicarbonyls were degraded during aging. Advanced glycation end products as possible degradation products showed no consistent formation during aging. Therefore, Strecker reactions were favored during beer aging. No alternative oxidative formation of Strecker aldehydes from their corresponding alcohols could be confirmed. Along with the preceding part one of our investigation, the results of this study showed that de novo formation and release occur simultaneously. After 4 months of natural aging, aldehyde rise is mainly accounted for by de novo formation.

Effect of post-milling process on the oxidation of the rice bran

“…These amino acids have been previously identi ed in the rice bran and have been reported in our previous study(Najamuddin, Gorji, & Fitzgerald, 2021). These compounds are aldehydes that have been considered as signi cantly related to storage time Strecker aldehydes(Nobis et al, 2021). Butanal 2-methyl and Butanal 3-methyl identi ed in this study contribute to the malty and nutty avour of the bran(Smit, Engels, & Smit, 2009).…”

Assessment of Staling Aldehydes in Lager Beer under Maritime Transport and Storage Conditions

“…In their bound-state, they are undetectable in fresh beer and the same is true for their sensory perception [7,15,16]. More recently, it has been reported that during beer aging the release of bound-state aldehydes and their de novo formation occur simultaneously, although de novo formation during natural aging is more prevalent after four months [17]. Therefore, the presence of these carbonyl compounds, either in their free or bound state form, and their precursors for de novo formation, define the aging potential of the final beer, which can easily vary according to the brewing process and raw materials applied [18].…”

Sources of Volatile Aromatic Congeners in Whiskey

“…The amino acid can undergo either Strecker degradation (SD) with an α-dicarbonyl or an Amadori rearrangement (AR) with an α-hydroxycarbonyl, both of which produce Strecker aldehydes. AR-produced Strecker aldehydes will go on to produce melanoidins, brown, high molecular weight polymers, whereas SD-produced Strecker aldehydes [46,47]. Key Strecker aldehydes are 2-methylpropanal (derived from valine), 2-methybutanal (derived from isoleucine), 3-methylbutanal (derived from leucine), methional (derived from methionine), and phenylacetaldehyde (derived from phenylalanine).…”