Effect of Oxygen Supply on Flavor Formation during Continuous Alcohol-Free Beer Production: A Model Study

Lehnert, Radek; Kuřec, Michal; Brányik, Tomáš; Teixeira, J. A.

doi:10.1094/asbcj-2008-0910-01

Cited by 15 publications

(13 citation statements)

References 29 publications

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“…It has been observed, however, that those process conditions, e.g. temperature and aeration, that can be used to control higher alcohol and ester production during regular continuous fermentation can also be applied when the desired product is a low‐alcohol beer (van Iersel et al, ; Lehnert et al, ). The relatively low levels of aroma compounds frequently associated with limited fermentations may be overcome by appropriate yeast strain selection or, alternatively, through modification of an existing strain to promote volatile production (Strejc et al, ).…”

Section: Case Studies: Brewingmentioning

confidence: 99%

Aroma formation by immobilized yeast cells in fermentation processes

Nedović

Gibson

Mantzouridou

et al. 2014

Yeast

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Immobilized cell technology has shown a significant promotional effect on the fermentation of alcoholic beverages such as beer, wine and cider. However, genetic, morphological and physiological alterations occurring in immobilized yeast cells impact on aroma formation during fermentation processes. The focus of this review is exploitation of existing knowledge on the biochemistry and the biological role of flavour production in yeast for the biotechnological production of aroma compounds of industrial importance, by means of immobilized yeast. Various types of carrier materials and immobilization methods proposed for application in beer, wine, fruit wine, cider and mead production are presented. Engineering aspects with special emphasis on immobilized cell bioreactor design, operation and scale-up potential are also discussed. Ultimately, examples of products with improved quality properties within the alcoholic beverages are addressed, together with identification and description of the future perspectives and scope for cell immobilization in fermentation processes.

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Section: Case Studies: Brewingmentioning

confidence: 99%

Aroma formation by immobilized yeast cells in fermentation processes

Nedović

Gibson

Mantzouridou

et al. 2014

Yeast

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show abstract

“…In terms of solid concentration, the following four solid loadings were used: 0%, 2%, 4%, 6% (wt WET BASIS / vol). These are also similar to the ones used in continuous systems using immobilized cells in spent grains (Lehnert et al, 2008;Mota et al, 2011).…”

Section: Experimental Conditionsmentioning

confidence: 65%

Customization of an optical probe device and validation of a signal processing procedure to study gas–liquid–solid flows. Application to a three-phase internal-loop gas-lift Bioreactor

Mota

Ferreira

Vicente

et al. 2015

Chemical Engineering Science

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a b s t r a c tThe study of local hydrodynamic properties of three-phase bioreactors in biotechnology processes is of great importance, mainly because of the complex interaction between bioreactor and microorganisms. However, classical techniques used for measuring local hydrodynamic properties such as single needle probes are mainly limited to two-phase flows. In this work it was developed and validated a new system, based on the customization of an optical probe initially designed in LEGI. The necessity of a new system was due to the agglomeration of the solid-phase (spent grains which are used as the micro-organisms carrier for the targeted application) around the optical tip, which influences the measurements. This new system allows for the measurement of the main local gas-phase properties in a complex gas-liquid-solid mixture. The new system was first validated for air-water system in an internal loop gas-lift reactor and then applied to a spent grains-air-water mixture at low solid load in an internal gas lift reactor. In addition, experiments using complementary techniques (as high speed camera and PIV) were performed that allowed for the validation of the new system and the explanation of possible physical mechanisms that are underlying on this multiphase system. The system developed has the potential for improvement and use in several biotechnology applications.

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“…In order to avoid the often observed under-or over-aeration in continuous beer fermentation systems, it was necessary to determine the volumetric oxygen mass transfer coefficient (k L a) under real fermentation conditions. The oxygen transfer rate (OTR) during real fermentation experiments was calculated using the k L a (0.98 ± 0.5 h -1 ) determined for the solid loading of 14 g of dry spent grains per unit reactor volume (Lehnert et al 2008). The influence of the OTR on the flavour active compounds was studied in a range from 1 to 12 mg O 2 /lh at a constant temperature (8°C) and residence time (6.5 h).…”

Section: Optimisation Of Process Parameters In Model Medium: Aerationmentioning

confidence: 99%

Optimisation of lab-scale continuous alcohol-free beer production

Lehnert¹,

Novák²,

Macieira³

et al. 2009

Czech J. Food Sci.

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Lehnert R., Novák P., Macieira F., Kuřec M., Teixeira J.A., Branyik T. (2009): Optimisation of labscale continuous alcohol-free beer production. Czech J. Food Sci., 27: 267-275.In order to study the formation and conversion of the most important flavour compounds, the real wort used in alcohol-free beer fermentation was mimicked by a complex model medium containing glucose, yeast extract, and selected aldehydes. The fermentation experiments were carried out in a continuously operating gas-lift reactor with brewing yeast immobilised on spent grains (brewing by-product). During the continuous experiment, parameters such as oxygen supply, residence time (Rt), and temperature (T) were varied to find the optimal conditions for the alcohol-free beer production. The formation of ethanol, higher alcohols (HA), esters (ES), as well as the reduction of aldehydes and consumption of glucose were observed. The results suggest that the process parameters represent a powerful tool in controlling the degree of fermentation and flavour formation brought about by immobilised biocatalyst. Subsequently, the optimised process parameters were used to produce real alcohol-free beer during continuous fermentation. The final product was compared with batch fermented alcohol-free beers using the methods of instrumental and sensorial analysis.

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Effect of Oxygen Supply on Flavor Formation during Continuous Alcohol-Free Beer Production: A Model Study

Cited by 15 publications

References 29 publications

Aroma formation by immobilized yeast cells in fermentation processes

Aroma formation by immobilized yeast cells in fermentation processes

Customization of an optical probe device and validation of a signal processing procedure to study gas–liquid–solid flows. Application to a three-phase internal-loop gas-lift Bioreactor

Optimisation of lab-scale continuous alcohol-free beer production

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