Continuous beer fermentation - diacetyl as a villain

Abstract

This work tested the viability of producing beer of good quality after maturation of green beer obtained by primary continuous fermentation of high-gravity wort using an airlift bioreactor with flocculated biomass. Fermentation performance of the tested setup was unique as it reached a maximum saccharide consumption rate of 9.43 g L À1 h À1 and an ethanol productivity of 3.75 g L À1 h À1 . Despite the high levels of diacetyl present in the green beer, a regular maturation was able to reduce it to below threshold values in up to 15 days. It was observed that diacetyl production was strongly correlated with wort composition injected into the system, rather than with the large amount of biomass immobilized in the bioreactor (up to 727 × 10 6 cell mL À1 ). Organoleptic tests showed that the maturated beer had no major defects.

Assessing Population Diversity of Brettanomyces Yeast Species and Identification of Strains for Brewing Applications

“…Most of the diacetyl-related ILV genes are located in centromeric-like regions and conserved in B. bruxellensis strains. As this off-flavor is linked to the fermentation-maturation stage of the beer, and its flavor detection threshold is remarkably low, it can become challenging to rush into certain conclusions for production and prevention of this metabolite (Dasari and Kölling, 2011;Pires et al, 2015).…”

Cinnamil- and Quinoxaline-Derivative Indicator Dyes for Detecting Volatile Amines in Fish Spoilage

“…Both substrates for cinnamil synthesis are commonly encountered in food. Diacetyl ( 1 in Scheme 1; or 2,3-butanedione) is naturally occurring in butter, margarine, coffee, beer, and dairy products, as a buttery flavor ingredient [13,14,15]. On the other hand, benzaldehyde ( 2a in Scheme 1) is naturally present in almond, which is often serving as a food additive to mimic almond and cherry flavor [16,17].…”

Packing a punch: understanding how flavours are produced in lager fermentations

“…For instance, diacetyl and 2, 3-pentadione – by-products from valine and isoleucine biosynthesis in yeasts (Krogerus and Gibson 2013a ), are described as butterscotch and undesirable in lager beer (Pires et al . 2015 ). In addition, sulphur compounds such as hydrogen sulphide (H 2 S) and dimethyl sulphide (DMS) are off-odours.…”