Continuous beer fermentation diacetyl as a villain

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 L1 h1 and an ethanol productivity of 3.75 g L1 h1. 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 × 106 cell mL1). Organoleptic tests showed that the maturated beer had no major defects.Eduardo Pires gratefully acknowledges the Fundacao para a Ciencia e a Tecnologia (FCT, Portugal) for PhD fellowship support (SFRH/BD/61777/2009). All material supplied by UNICER Bebidas de Portugal, S.A. (S. Mamede de Infesta, Portugal) as well as the technical support of company members Sonia Meireles and Helena Cunha is gratefully acknowledged. The financial contributions of the EU FP7 project EcoBioCAP - Ecoefficient Biodegradable Composite Advanced Packaging, grant agreement no. 265669 as well as of the Ministry of Education, Youth and Sports of the Czech Republic (MSM 6046137305) are gratefully acknowledged

A review of flavour formation in continuous beer fermentations

The attractive prospect of a continuous beer fermentation system consists mostly of the accelerated transformation of wort into beer. Although continuous beer fermentation has been studied as a promising technology for several decades, the number of industrial applications is still limited. The major obstacle hindering the extensive industrial exploitation of this technology is the difficulty in achieving the correct balance of sensory compounds in the short time typical for continuous systems. This paper offers an integral view on the particularities of continuous systems, which may impart beer a sensorial character distinct from conventionally fermented counterparts. The main groups of flavour active compounds are discussed from the perspective of possible control strategies by means of process parameters and strain selection.Czech Grant Agency; MŠM

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

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 (packedbed) 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.(Fundação de Amparo a Pesquisa do Estado de São Paulo, Brazil (FAPESPFundação para a Ciência e a Tecnologia (FC

Antioxidative Activity of Intermediate Products in Brewing.

By means of FRAP (Ferric Reducing Ability of Plasma) method, based on ferric tripyridyltriazine complex by the antioxidants from sample was measured the antioxidative activity of sweet wort (equivalent of 1.92 mmol reduced iron per liter), hopped wort (2.46 mmol.l-1), green beer (1.89 mmol.l-1) and beer after maturation (1.63 mmol.l-1). The antioxidative activity of some beers from market varied between 1.52-2.57 mmol.l-1 (in case of alcoholic beers) and 0,95-1.46 mmol.l-1 (non-alcoholic beers).By means of FRAP (Ferric Reducing Ability of Plasma) method, based on ferric tripyridyltriazine complex by the antioxidants from sample was measured the antioxidative activity of sweet wort (equivalent of 1.92 mmol reduced iron per liter), hopped wort (2.46 mmol.l-1), green beer (1.89 mmol.l-1) and beer after maturation (1.63 mmol.l-1). The antioxidative activity of some beers from market varied between 1.52-2.57 mmol.l-1 (in case of alcoholic beers) and 0,95-1.46 mmol.l-1 (non-alcoholic beers)

Wort Preparation and its Influence to Fermentation and Beer Properties.

Wort preparation is very important step from the view of fermentation run and finish beer quality as well.Wort properties affect incoming raw materials and technological process of its production.Yeast and fermentation process play very important role in beer production and for that reason it is necessary to prepare wort in the way to content important nutrients: carbon source (fermentable saccharides), oxygen and lipides (lipides for membrane biosynthesis, which yeast can realize in oxygen presence), nitrogen source (aminoacids and peptides are necessary for yeast growth and enzyme synthesis), growth factors - vitamins, inorganic ions (important for yeast metabolism) and water. Article brings view of individual parameters and simultaneously discusses their influence on fermentation run and finish beer quality.Wort preparation is very important step from the view of fermentation run and finish beer quality as well.Wort properties affect incoming raw materials and technological process of its production.Yeast and fermentation process play very important role in beer production and for that reason it is necessary to prepare wort in the way to content important nutrients: carbon source (fermentable saccharides), oxygen and lipides (lipides for membrane biosynthesis, which yeast can realize in oxygen presence), nitrogen source (aminoacids and peptides are necessary for yeast growth and enzyme synthesis), growth factors - vitamins, inorganic ions (important for yeast metabolism) and water. Article brings view of individual parameters and simultaneously discusses their influence on fermentation run and finish beer quality

Comparison of the content of volatile sulphur-containing compounds in Slovak beers by the SPME method.

A comparison of volatile sulphur-containing compounds in Slovak beers was performed. These compounds, due to their low sensory threshold, and powerful and often unpleasant characteristics, can cause off-odours even in trace amounts. A wide variety of sulphur compounds were identified in the beers; the most important ones include dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide, ethanethiol, ethyl thioacetate, methanethiol, methionol, methyl thioacetate, 3-methylthio propylacetate and carbon disulphide. In the first step, adsorption conditions, such as temperature, time, sample volume and addition of salts, were optimised. The content of volatile sulphur-containing compounds was measured using headspace solid-phase micro-extraction (SPME) coupled with gas chromatography and flame photometric detection (GC-FPD). Two internal standards were used - ethyl methyl sulphide and 1-propyl thioacetate. Differences in the profiles of individual compounds in different beer brands as well as differences in the amounts of sulphur-containing compounds in beers with different gravity were found.A comparison of volatile sulphur-containing compounds in Slovak beers was performed. These compounds, due to their low sensory threshold, and powerful and often unpleasant characteristics, can cause off-odours even in trace amounts. A wide variety of sulphur compounds were identified in the beers; the most important ones include dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide, ethanethiol, ethyl thioacetate, methanethiol, methionol, methyl thioacetate, 3-methylthio propylacetate and carbon disulphide. In the first step, adsorption conditions, such as temperature, time, sample volume and addition of salts, were optimised. The content of volatile sulphur-containing compounds was measured using headspace solid-phase micro-extraction (SPME) coupled with gas chromatography and flame photometric detection (GC-FPD). Two internal standards were used - ethyl methyl sulphide and 1-propyl thioacetate. Differences in the profiles of individual compounds in different beer brands as well as differences in the amounts of sulphur-containing compounds in beers with different gravity were found

The production of alcohol free beers with citric acid cycle defect.

For production of alcohol free beer was used  Saccharomyces cerevisiae with citric acid cycle defect. The ethanol concentration of all beers, produced in charge or continuos process by means of traditional or immobilised yeast was negligible, significantly below 0,5% (vol). The strain Saccharomyces cerevisiae W303 proved to be as the best one. This immobilised strain in charge process produced nearly 640 mg lactic and organic acids improving sensory properties of beer and protecting beer from bacterial contamination. The sensory properties of the alcohol free beer were comparable with traditional beer produced by means of bottom yeast Saccharomyces cerevisiae W96.  For production of alcohol free beer was used  Saccharomyces cerevisiae with citric acid cycle defect. The ethanol concentration of all beers, produced in charge or continuos process by means of traditional or immobilised yeast was negligible, significantly below 0,5% (vol). The strain Saccharomyces cerevisiae W303 proved to be as the best one. This immobilised strain in charge process produced nearly 640 mg lactic and organic acids improving sensory properties of beer and protecting beer from bacterial contamination. The sensory properties of the alcohol free beer were comparable with traditional beer produced by means of bottom yeast Saccharomyces cerevisiae W96

Effect of trub, oxygen content and hopped wort pH on the course of fermentation.

The effects of the properties of hopped worts on the course of fermentationand beer character were monitored in this work. Hoppedwort pH in the range of 5,1-5,4 has insignificant effects on the speedof primary fermentation, the breakdown of diacetyl was faster in caseof hopped worts with pH = 5,1 (6,9 days), the slowest diacetyl breakdownwas observed for hopped worts with pH = 5,4 (11,4 days). Fromorganoleptic point of view, finished beers prepared from hopped wortswith a higher pH were preferred.With different wort aeration (8 mg/l, 9 mg/l and 10 mg/l of oxygen),no differences were observed during fermentation. The day of yeastremoval from cylindro-conical fermenters, decrease in diacetyl contentas well as the number of dead yeast cells (to 2 %) were comparable.In case of hopped worts with a higher trub content, 1 day longerbreakdown of vicinal diketones (diacetyl) to the value required,lower foam stability (by 5 s - 2 %) and a lower colloidal stability(approx. by 3 weeks - 9 %) were observed, but no differences inthe organoleptic properties of fresh beers. In case of infusion mashing,a higher haze level at the angle of 90° and a lower haze levelat the angle of 15° were observed in unhopped wort. In hoppedwort, a higher haze level in case of infusion mashing as wellas during decoction mashing at the angle of 90° and 15° was observed.The effects of the properties of hopped worts on the course of fermentationand beer character were monitored in this work. Hoppedwort pH in the range of 5,1-5,4 has insignificant effects on the speedof primary fermentation, the breakdown of diacetyl was faster in caseof hopped worts with pH = 5,1 (6,9 days), the slowest diacetyl breakdownwas observed for hopped worts with pH = 5,4 (11,4 days). Fromorganoleptic point of view, finished beers prepared from hopped wortswith a higher pH were preferred.With different wort aeration (8 mg/l, 9 mg/l and 10 mg/l of oxygen),no differences were observed during fermentation. The day of yeastremoval from cylindro-conical fermenters, decrease in diacetyl contentas well as the number of dead yeast cells (to 2 %) were comparable.In case of hopped worts with a higher trub content, 1 day longerbreakdown of vicinal diketones (diacetyl) to the value required,lower foam stability (by 5 s - 2 %) and a lower colloidal stability(approx. by 3 weeks - 9 %) were observed, but no differences inthe organoleptic properties of fresh beers. In case of infusion mashing,a higher haze level at the angle of 90° and a lower haze levelat the angle of 15° were observed in unhopped wort. In hoppedwort, a higher haze level in case of infusion mashing as wellas during decoction mashing at the angle of 90° and 15° was observed

Exploitation possibilities of glucose-maltose syrups in substitution of wort extract.

The work compares the glucose-maltose syrups and saccharose from the point of view of their utilization as replacements of part of wort extract in production of the 12= beer. The attenuation degree as well as the amount of produced ethanol in beer increase proportionally to the percentage of the substitute while the quality of nitrogenous matters and polyphenols, together with the temperature and colour of beer fall. Those changes became less evident in the mentioned syrups then in saccharose. The best result was achieved with the preparator Fermentose 352. When the extract was replaced by the mentioned preparator instead of by saccharose, the amount of diacetyl in hopped wort did not raise and decrease of amount of higher alcohols and of esters appeared only after the extract substitution surpassed 30 %.The work compares the glucose-maltose syrups and saccharose from the point of view of their utilization as replacements of part of wort extract in production of the 12= beer. The attenuation degree as well as the amount of produced ethanol in beer increase proportionally to the percentage of the substitute while the quality of nitrogenous matters and polyphenols, together with the temperature and colour of beer fall. Those changes became less evident in the mentioned syrups then in saccharose. The best result was achieved with the preparator Fermentose 352. When the extract was replaced by the mentioned preparator instead of by saccharose, the amount of diacetyl in hopped wort did not raise and decrease of amount of higher alcohols and of esters appeared only after the extract substitution surpassed 30 %

Temperature Influence on Fermentation Speed and Organoleptic Beer Properties.

The objective of this work was to study temperature changes during the process of primary and secondary fermentation and their effect on fermentation speed, foam stability and organoleptic properties of beer. The experiments were carried out with 13 % hopped worts, with pitching temperature of 8,5 °C and temperature control from 10 and 13 °C to 14 °C during primary fermentation. For fermentation, production strains of brewery yeast Saccharomyces cerevisiae, variety uvarum W 34/70 were used. By changing temperature during the primary fermentation process and by keeping this temperature also during secondary fermentation, good organoleptic properties of beer were obtained (palatefulness, bitterness and body), together with foaming power, and faster fermentation process.The objective of this work was to study temperature changes during the process of primary and secondary fermentation and their effect on fermentation speed, foam stability and organoleptic properties of beer. The experiments were carried out with 13 % hopped worts, with pitching temperature of 8,5 °C and temperature control from 10 and 13 °C to 14 °C during primary fermentation. For fermentation, production strains of brewery yeast Saccharomyces cerevisiae, variety uvarum W 34/70 were used. By changing temperature during the primary fermentation process and by keeping this temperature also during secondary fermentation, good organoleptic properties of beer were obtained (palatefulness, bitterness and body), together with foaming power, and faster fermentation process