Rapid maturation of beer using an immobilized yeast bioreactor. 1. Heat conversion of α-acetolactate

Despite extensive research carried out in the last few decades, continuous beer fermentation has not yet managed to outperform the traditional batch technology. An industrial breakthrough in favour of continuous brewing using immobilized yeast could be expected only on achievement of the following process characteristics: simple design, low investment costs, flexible operation, effective process control and good product quality. The application of cheap carrier materials of by-product origin could significantly lower the investment costs of continuous fermentation systems. This work deals with a complete continuous beer fermentation system consisting of a main fermentation reactor (gas-lift) and a maturation reactor (packed-bed) containing yeast immobilized on spent grains and corncobs, respectively. The suitability of cheap carrier materials for long-term continuous brewing was proved. It was found that by fine tuning of process parameters (residence time, aeration) it was possible to adjust the flavour profile of the final product. Consumers considered the continuously fermented beer to be of a regular quality. Analytical and sensorial profiles of both continuously and batch fermented beers were compared.

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“…Obviously, other strategies of enhanced maturation, e.g. heat treatment of young beer, should be pondered too [41].…”

Section: Discussionmentioning

confidence: 99%

Continuous immobilized yeast reactor system for complete beer fermentation using spent grains and corncobs as carrier materials

Brányik

Silva²,

Vicente

et al. 2006

J Ind Microbiol Biotechnol

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“…The total diacetyl level of the normal cell density fermentations increased after G2 and stabilized to a certain level (0.26 ppm), which was significantly lower than the HCD conditions. As the chemical decarboxylation is the rate-limiting step in the metabolism of diacetyl (Yamauchi et al 1995), the increase in total diacetyl in the REF condition after the first two generations could be explained by insufficient chemical decarboxylation due to the faster fermentation rate of the REF condition since G2 (Fig. 1a).…”

Section: Fermentation Characteristicsmentioning

confidence: 96%

Stability of high cell density brewery fermentations during serial repitching

et al. 2009

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The volumetric productivity of the beer fermentation process can be increased by using a higher pitching rate (i.e. higher inoculum size). However, the decreased yeast net growth observed in these high cell density brewery fermentations can adversely affect the physiological stability throughout subsequent yeast generations. Therefore, different O(2) conditions (wort aeration and yeast preoxygenation) were applied to high cell density fermentation and eight generations of fermentations were evaluated together with conventional fermentations. Freshly propagated high cell density populations adapted faster to the fermentative conditions than normal cell density populations. Preoxygenating the yeast was essential for the yeast physiological and beer flavor compound stability of high cell density fermentations during serial repitching. In contrast, the use of non-preoxygenated yeast resulted in inadequate growth which caused (1) insufficient yield of biomass to repitch all eight generations, (2) a 10% decrease in viability, (3) a moderate increase of yeast age, (4) and a dramatic increase of the unwanted flavor compounds acetaldehyde and total diacetyl during the sequence of fermentations. Therefore, to achieve sustainable high cell density fermentations throughout the economical valuable process of serial repitching, adequate yeast growth is essential.

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“…The diacetyl is then reduced to acetoin during maturation with continuous immobilized yeast system operating at a residence time of 2 h. Nevertheless, to avoid formation of off-flavors, yeast must be removed from the green beer and oxygen pick up must be prevented (6,69,70).…”

Section: Flavor Problems Of Beer Produced By Immobilized Brewing Yeastmentioning

confidence: 99%

Continuous Beer Fermentation Using Immobilized Yeast Cell Bioreactor Systems

Brányik

Vicente

Dostálek

et al. 2008

Biotechnol Progress

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Traditional beer fermentation and maturation processes use open fermentation and lager tanks. Although these vessels had previously been considered indispensable, during the past decades they were in many breweries replaced by large production units (cylindroconical tanks). These have proved to be successful, both providing operating advantages and ensuring the quality of the final beer. Another promising contemporary technology, namely, continuous beer fermentation using immobilized brewing yeast, by contrast, has found only a limited number of industrial applications. Continuous fermentation systems based on immobilized cell technology, albeit initially successful, were condemned to failure for several reasons. These include engineering problems (excess biomass and problems with CO(2) removal, optimization of operating conditions, clogging and channeling of the reactor), unbalanced beer flavor (altered cell physiology, cell aging), and unrealized cost advantages (carrier price, complex and unstable operation). However, recent development in reactor design and understanding of immobilized cell physiology, together with application of novel carrier materials, could provide a new stimulus to both research and application of this promising technology.

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Rapid maturation of beer using an immobilized yeast bioreactor. 1. Heat conversion of α-acetolactate

Cited by 28 publications

References 5 publications

Continuous immobilized yeast reactor system for complete beer fermentation using spent grains and corncobs as carrier materials

Continuous immobilized yeast reactor system for complete beer fermentation using spent grains and corncobs as carrier materials

Stability of high cell density brewery fermentations during serial repitching

Continuous Beer Fermentation Using Immobilized Yeast Cell Bioreactor Systems

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