Release of Deuterated Nonenal during Beer Aging from Labeled Precursors Synthesized in the Boiling Kettle

Abstract

The use of labeled nonenal enabled the demonstration that the appearance of the cardboard flavor in finished beer comes from lipid auto-oxidation during wort boiling and not from lipoxygenasic activity during mashing. Free trans-2-nonenal produced by linoleic acid auto-oxidation in the kettle disappears, owing to retention by wort amino acids and proteins. This binding linkage protects trans-2-nonenal from yeast reduction but is reversible, allowing release of the compound at lower pH during aging. Labeled trans-2-nonenal is detected after aging when deuterated precursors form in the boiling kettle. The amount of alkenal released correlates with the concentration of reversible associations in the pitching wort. This work brings new illumination to the formation of trans-2-nonenal and overturns many previous hypotheses. It also explains why a reduction in the beer pH intensifies the cardboard flavor.

The Role of Malt and Hop Polyphenols in Beer Quality, Flavour and Haze Stability

“…Both malt and hops are sources of beer polyphenol substances and the quality of raw materials can affect sensory stability 5,23 . Dependence of reducing activity and beer flavour stability based on the malt polyphenol content and composition has been reported by some authors 5,19,30 , and the significant effect of hop polyphenols on reducing activity and stale flavour carbonyl formation in beer was demonstrated by other authors 22,23,32 . Beer flavour deterioration depends on both the quantity and the quality of polyphenols in beer [52][53][54] and the protective action of polyphenols is important especially during mashing 19 and wort boiling 19,32 , which are probably the determining steps in beer flavour stability 32 .…”

Catechins and Derived Procyanidins in Red and White Sorghum: Their Contributions to Antioxidant Activity

“…The fact that sorghum is gluten-free increases brewers' interest in using sorghum, as it raises the possibility of producing beers for coeliacs. Probably also due to its very high polyphenolic content, sorghum is recognized by brewers as efficiently limiting the cardboard off-flavour (trans-2-nonenal) in aged beers, by inhibiting lipid oxidation during mashing and boiling 9,10,19,21 .…”

Fate of 2-sulphanylethyl acetate and 3-sulphanylpropyl acetate through beer aging

“…What about their fate in beer? Beer aging defects, especially linked to Strecker aldehydes , trans ‐non‐2‐enal , dimethyltrisulphide , β ‐damascenone , 4‐vinylsyringol and ethylfurfurylether , have been extensively investigated, but very little is yet known about polyfunctional thiols and their possible synergy with other aged flavours . To our knowledge, only 3‐sulphanyl‐3‐methylbutyl formate, with a catty, ribes aroma, has been reported to increase upon accelerated aging .…”