Modeling Of Alcohol Fermentation In Brewing - Integrated Approch For Control Of Continuous Alcohol Fermentation
An integrated approach for the management of continuous beer fermentation with immobilized cells was developed. Experimental results for continuous fermentation were used for the development of dependencies for the calculation of real extract and ethanol at different degrees of fermentation and dilution rates. For this purpose, mathematical relationships describing the fermentation with high accuracy were used.
Immobilized cell technology in beer brewing: Current experience and results
Immobilized cell technology (ICT) has been attracting continual attention in the brewing industry over the past 30 years. Some of the reasons are: faster fermentation rates and increased volumetric productivity, compared to those of traditional beer production based on freely suspended cells, as well as the possibility of continuous operation. Nowadays, ICT technology is well established in secondary fermentation and alcohol- free and low-alcohol beer production. In main fermentation, the situation is more complex and this process is still under scrutiny on both the lab and pilot levels. The paper outlines the most important ICT processes developed for beer brewing and provides an overview of carrier materials, bioreactor design and examples of their industrial applications, as well as some recent results obtained by our research group. We investigated the possible applications of polyvinyl alcohol in the form of LentiKats®, as a potential porous matrices carrier for beer fermentation. Given are the results of growth studies of immobilized brewer's yeast Saccharomyces uvarum and the kinetic parameters obtained by using alginate microbeads with immobilized yeast cells and suspension of yeast cells as controls. The results indicate that the immobilization procedure in LentiKat® carriers has a negligible effect on cell viability and growth. The apparent specific growth rate of cells released in medium was comparable to that of freely suspended cells, implying preserved cell vitality. A series of batch fermentations performed in shaken flasks and an air-lift bioreactor indicated that the immobilized cells retained high fermentation activity. The full attenuation in green beer was reached after 48 hours in shaken flasks and less than 24 hours of fermentation in gas-lift bioreactors.
Productivity of Immobilized Yeast Reactors with Very-High-Gravity Worts
In the competitive world of beer production, efficient utilization of raw materials and equipment together with smooth operation are advantageous. In this study, data from laboratory-scale main fermentations with original gravities between 15 and 24°P and immobilized yeast are presented. The worts were prepared from malt extract, and lower original gravities were obtained by diluting the 24°P wort with brewery water. The yeast strain used was a production strain from a brewery. Porous glass beads were used as the carrier. The optimal gravity found in regard to ethanol productivity was between 18 and 21°P. The highest ethanol concentration in the beers was over 10% (v/v). The aroma compound profiles of the beers produced were quite similar, except for acetaldehyde. The laboratory-scale fermentations using immobilized yeast may be an effective tool to screen for ethanol-tolerant strains or to find process parameters that facilitate very-high-gravity brewing.