Decrease of Aged Beer Aroma by the Reducing Activity of Brewing Yeast

Abstract

The flavor profile of beer is subject to changes during storage. Since, possibly, yeast has an influence on flavor stability, the aim of this study was to examine if there is a direct impact of brewing yeast on aged aroma. This was achieved by refermentation of aged beers. It was shown that several aged aroma notes, such as cardboard, ribes, Maillard and Madeira, were removed almost entirely by brewing yeast, independently of the yeast or the beer type. This was explained by the reduction of aldehydes, mainly (E)-2-nonenal, Strecker aldehydes, 5-hydroxymethylfurfural and diacetyl, to their corresponding alcohols. Furthermore, it became evident that the reducing capacity of brewing yeast is high, but that yeast strain and compound specific residual concentrations remained in the refermented beer independently of the initial concentration. Finally, it appeared that aldehydes were not only reduced but also formed during refermentation.

Conventional and Non-Conventional Yeasts in Beer Production

“…The use of yeasts with limited abilities to utilise wort sugars, i.e., maltose-negative yeasts, but that produce typical concentrations of aroma compounds, is a useful alternative to produce low-alcohol beers that still retain some of the aromatic complexity of standard beers. Such yeasts will also reduce wort aldehydes, thereby removing the "worty" taste that is often found in low-alcohol beers produced by arrested fermentation [42]. Different non-Saccharomyces species can be used for these productions.…”

Occurrence of the ribes odorant 3‐sulfanyl‐3‐methylbutyl formate in aged beers

“…Polyfunctional thiols were selectively extracted by p-HMB from five lager (L1-L3 and P1-P2) and six top-fermentation (T1-T6) beers and analysed by GC-PFPD ( Table 2). None of the investigated fresh commercial Belgian beers exhibited a PFPD peak at the retention time of 3-sulfanyl-3-methylbutyl formate (1) or acetate (2). Compounds 3 and 4 were also below the PFPD detection limit (7 ng/l) in all samples.…”

“…Chromatographic and Sensorial Data of 2-and 3-Sulfanyl-3-methylbutyl Formates and Acetates 2-Sulfanyl-3-methylbutyl formate (compound 3) and acetate (4) were obtained by combinatorial synthesis without further purification, just to be compared with commercially available 3-sulfanyl-3-methylbutyl formate (1) and acetate (2). As depicted in Figure 1, GC-HRMS allowed us to confirm the structures of 3 and 4 (calculated m/z for 3, 102.0503; found, 102.0504; difference, 1.0 ppm; calculated m/z for 4, 102.0503; found, 102.0506, difference, 2.9 ppm; well within the variation range of the apparatus).…”

“…After 3 months (Figure 3c), 1 was found to have decreased to 253 ng/l. According to Clapperton [1] and Saison, [2] the ribes defect can be linked to the presence of a higher level of oxygen in the bottle. Our two pilot beers were less oxygen-protected, as they were not bottled industrially.…”

“…On the other hand, according to Clapperton, [1] ribes notes arise solely because of excessive amounts of air in the headspace. More recently, the key role of oxygen was confirmed by Saison et al [2] The ribes odour can develop within 4 weeks of bottling. In many beers, the note is no longer discernible after 6 months.…”