Session Chair:
Gert De Rouck (Managing Director Pilot Malting & Brewery – EFBT, KU Leuven, BE)
Barley Varietal Impact on the Levels of Assimilable Nitrogen and Precursors for Strecker Degradation in Beer
By Xiang S. Yin et al., Rahr Malting Co.
Barley Varietal Impact on the Levels of Assimilable Nitrogen and Precursors for Strecker Degradation in Beer Xiang S Yin, Sean Tynan, Emily Del Bel, Kain Escobar, Pattie Aron Rahr Corporation, USA Based on a set of worldwide malt samples of >70 barleys from 20 plus varieties, cluster analyses demonstrated significant relationship between pattern of amino acid (AA) composition and sample origins. Substantial differences were observed in the relative content of proline (un-assimilable) between two-row (2R) and six-row (6R) varieties. In contrast to the 2R varieties, 6R samples showed a general trend of low proline and high levels of important and crucial AAs. Within 2R varieties, e.g. Metcalfe and Explorer grown in USA, the AA spectra were variety dependent. While within one variety the ratio of classes of AAs released from malt did not vary significantly with malting process, the total assimilable nitrogen varied by up to 10% depending on variety. The residual S-containing AAs impact the beer flavor profile and the Strecker Degradation AAs are key factors in the flavor stability of packaged beers, particularly all-malt brews. Impacts of heat stress on proline has been explored.
Maillard reactions in beer: 3-desoxyglucosone and flavour instability
By Melanie Kwasnicki et al., TU Dresden
During Strecker degradation, flavour active aldehydes are formed from amino acids and dicarbonyl compounds After bottling, the amount of these aldehydes increase during beer aging, thus leading to flavour instability. 3-deoxyglucosone (3-DG) is the most important dicarbonyl compound that results either from Maillard reaction or from caramelization. At beer production, malt provides a basic potential of 3-DG which increases by wort boiling. The malt modification level influences the amount of amino acids. In this study, six pale lager beers were brewed out of two barley varieties each with three different proteolytic malt modification levels. During a natural storage of nine months, precursor substances and Strecker aldehydes as well as the sensory character were analysed. It could be shown that a higher malt modification leads to higher concentrations of precursor substances like 3-DG as well as Strecker aldehydes in beer. During storage an increase of Strecker aldehydes and a decrease of 3-DG could be observed. Furthermore, de novo formation of Strecker aldehydes plays a role during ageing up to one to four months.
Untargeted metabolomic profiling of the differences between 100% malt beers and those made with unmalted barley adjunct
By David Cook et al., Nottingham University
Use of unmalted barley is an established practice in commercial brewing, which can offer cost savings, reductions in carbon and water footprints and opportunities for novel recipe development or functionality. As the proportion of unmalted barley in the grist increases, modifications to brewing protocols become necessary and the sensory properties of finished beers become distinct from those of all-malt beers. Beers brewed with 45% raw barley were characterised sensorially by a lingering bitterness and astringency. Moreover, they exhibited a lack of malty ‘fullness’ as opposed to having specific flavours imparted by raw barley. In this untargeted metabolomic study UHPLC-qTOF-MS was used to identify molecular features which differentiated unmalted barley adjunct beers from all-malt controls. This enabled identification of candidate groups of compounds which could be linked to the sensory differences between the beers, which targeted analysis of the ‘usual suspects’ (e.g. polyphenols, proanthocyanins) was not able to determine. In particular, nitrogenous fractions related to protein and purine breakdown were key differentiators and their potential sensory impacts will be discussed.
A technological measure to enhance mouthfeel in lager beers – can husk separation contribute to better beer quality?
By Jens Eiken, IFF et al.
Husk separation (also known as Kubessa process) is a well-established technique in lager beer brewing. Husk material is separated from starchy endosperm during milling and is only added back to the mash at the 72 °C rest to ensure good run-off at mash separation. This reduces the time required for polyphenols to leach into the mash. The result is an allegedly smoother and maltier beer with its bitterness originating mainly from hops, and not from any harshness imparted by the tannins or polyphenols, from the husk. However, this technique is rarely encountered outside of Germany. The authors have investigated the reasons for adhering to such a technology both from a sensory as well as marketing point of view, based on a survey conducted among some brewers practicing husk separation. Brewing trial results conducted at Distelhäuser Brewery will be compared with a view to establishing a link between husk separation and beer polyphenol analyses. A discussion on the possible beneficial effects this technology may have on drinkability and flavour / colloidal stability will conclude the presentation.