Lager flavour

Berliner weissen Lager Berlin 2.5-3 Lightly flavoured, mild... 

Another type of commercial hop extract is made by borohydride reduction of an isomerized extract of a-acids and is claimed to be less sensitive to light than a normal isomerized extract [124]. When beer, particularly lager beer, is exposed to sunlight in clear bottles it develops an unpleasant sun-struck flavour due to the formation of isopentenyl mercaptan (98). It is envisaged that photolysis of isohumulone cleaves the isohexenoyl side-chain to form a 3-methylbut-2-enyl radical which reacts with hydrogen sulphide, or any available thiol, in the beer to produce (98) [125]. 

Dimethyl sulphide (DMS, CHa-S-CHj) is recognized as making a significant contribution to beer flavour, particularly in lagers [87]. DMS is derived from a heat-labile precursor in malt it is also produced during fermentation. The heat-labile precursor of the DMS derived from malt is S-methyl meth-... 

The most important off-flavour and aroma associated with the lactic acid bacteria is the sweet, butterscotch or honey note provided by diacetyl and related vicinal diketones. It can be discerned readily in lager beers at concentrations as low as 0 5 (xg/ml. The defect was formerly called Sarcina sickness after Sarcina, the outdated generic name for brewery gram-positive bacteria. 

The formation of off-flavours in beer has been reviewed [40], Autoxidation of the lipids present in beer produces carbonyl compounds with very low taste thresholds. In particular, linoleic acid is oxidized to trihydroxyoctadecenoic acids (Table 22.7) which break down into 2-/mAz.y-nonenal. This aldehyde and related compounds impart a cardboard flavour to beer at very low concentrations. Other carbonyl are formed from the lipids in beer by irradiation with light including the C9, Cjo, and Cu-alka-2,4-dienals (thresholds 0 5, 0 3 and 0 01 ppb respectively) [40]. The level of diacetyl and pentane-2,3-dione in a range of commercial beers is given in Table 22.11. Quantities in excess of 0 15 ppm impart a buttery flavour more noticeable in lagers than in ales. Bacterial contamination and petite mutants of yeast result in high levels of diacetyl. The sulphur compounds characterized in beer are listed in Table 22.19 with some threshold data. Dimethyl sulphide is the major volatile... 

More complex correlations can be obtained by use of the computer. For example, national and regional differences in lager beers were examined by discriminant (cluster) analysis [53]. In this technique each beer is represented as a point in multi-dimensional space, the coordinates of which are determined either by the individual flavour characteristics, determined by profile analysis, or by physicochemical parameters, determined by analysis. Only 27 of the terms on the profile format (Fig. 23.8) gave significant scores with lagers. The pattern of points in 27-dimensional space is simplified by the computer programme to produce eigen vectors (mathematical devices to convert a pattern of points in multi-dimensional space into an equivalent pattern of points in a smaller number of dimensions). This has the ad-... 

The effects of pasteurisation are more apparent in lighter flavoured beers, which is why less PUs are typically applied to lagers than to ales and stouts. 

This chapter is divided into five sections including an introdnction (Section 17.1), impact of yeast on beer appearance (Section 17.2), impact of yeast on beer flavour (Section 17.3), impact of bacteria on beer appearance and flavour (Section 17.4), and future trends (Section 17.5). The emphasis is on the impact of yeast on beer appearance and flavour because more information is available on this topic. Although most of the discussions are centred on the impact of main brewing yeast strains (Saccharomyces cerevisiae and Saccharomycespastorianus) on barley malt-based beers (ale and lager, respectively) (Lodolo, Kock, Axcell, Brooks, 2008 Stewart, Hill, Russell, 2013), references are also made to other yeasts involved in brewing specialty beers derived from both barley malt and other cereal malts. Lactic acid bacteria (LAB) are the focus of discussion with regard to bacterial impact on beer appearance and flavour due to their relatively common occurrences in beers (Menz et al., 2010 Sakamoto Konings, 2003 Suzuki, 2011 Suzuki, Asano, lijima, Kitamoto, 2008). 

Strejc, J., Siristova, L., Karabin, M., Almeida e Silva, J. B., Branyik, T. (2013). Production of alcohol-free beer with elevated amounts of flavouring compounds using lager yeast mutants. Journal of the Institute of Brewing, 119,149-155. http //dx.doi.org/10.1002/jib.72. 

Takoi, K., Koie, K., Itoga, Y, Katayama, Y, Shimase, M., Nakayama, Y, et al. (2010). Biotrans-foimation of hop-derived monoterpene alcohols by lager yeasts and their contribution to the flavour of hopped beer. Journal of Agricultural and Food Chemistry, 58, 5050-5058. http //dx.doi.org/10.1021 /j f1000524. 

It is obvious that this absorbance includes other beer-extractable components, which absorb at 275 nm, in addition to the isohumulones. It is well established that iso-octane extracts about twice the weight from beer than the amount of iso-alpha acids present. The error in the absorbance measurement is, however, probably small, since these other components consist mainly of oxidized fatty acids (precursors of the sunstruck flavour. 15 to 20 mg.l " in lager beer) and other, non-UV active substances. 

The coated can is filled with a bottled or draught lager beer, left to stand, and then compared against a standard. Points of reference are changes in acidity, bitterness, and any metallic flavour compared to the standard. A trained and skilled flavour (taste) panel is normally used to assess this property. 

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