On the Measurement of the Flocculation Characteristics of Brewers' Yeast

Hamersveld, E. H. van; Loosdrecht, Mark C.M. van; Lans, R. G. J. M. van der; Luyben, K. Ch. A. M.

doi:10.1002/j.2050-0416.1996.tb00919.x

“…Since lager yeast strains are generally grown and adapted to much lower temperatures, the decrease in bond strength at higher temperatures may be caused by extraction of lectins from the yeast cell wall. The optimum temperature for flocculation was significantly higher than the 156C optimum observed by Van Hamersveld et al 24.…”

Section: Flocculation Characteristicscontrasting

confidence: 54%

Effect of Environmental Conditions on Flocculation and Immobilisation of Brewer's Yeast During Production of Alcohol-Free Beer

Iersel

¹

,

Meersman²,

Arntz

³

et al. 1998

Journal of the Institute of Brewing

17

0

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A method using immobilised yeasts has been developed and successfully applied for production of alcohol-free beer. The influence of environmental conditions present during alcohol-free beer production on the flocculation and immobilisation of the yeast Saccharomyces cerevisiae var. uvarum was investigated in the present study. In wort, the cells developed flocculation at the end of exponential growth, according to the NewFlo phenotype. In defined medium, the flocculation capacity appeared to be temporary and was lost rapidly during the stationary phase. No increase in cell wall hydrophobicity at the onset of flocculation was observed in either medium. Low growth temperatures increased flocculation capacity approximately four-fold, compared to growth at high temperatures. The optimum temperature for flocculation was at 25°C with cells grown at low or high temperature.A novel method using carboxyfluorescein-stained cells was developed to analyse the initial adhesion of cells to carrier. This method also allowed rapid analysis of the effects of immobilisation to DEAEcellulose carrier during alcohol-free beer production process. It appeared that a high flocculation capacity stimulated adhesion to the DEAE-carrier.

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“…The output of the apparatus is a ratio between two signals. This ratio is proportional to the size of the particles in the suspension (van Hamersveld et al, 1996).…”

Section: Flocculabilitymentioning

confidence: 99%

“…The settling velocity of an individual cell is low, and for this the cells of the nonflocculent strain will remain in suspension while the flocs of the flocculent strain will settle. In such a case, complete re- The relation between flocculability expressed as a ratio proportional to the floc size (van Hamersveld et al, 1996) and the diameter of yeast flocs at various power input levels. ⑀ ‫ס‬ 0.14 W/m 3 (), 0.5 W/m moval of the yeast cannot be achieved.…”

Section: Flocculability/floc Strengthmentioning

confidence: 99%

“…• From the moment the cells become flocculent, the flocculability, which represents the actual floc strength under favorable environmental conditions, also increases (van Hamersveld et al, 1996). The pH and sugar concentration of the medium, which both change during fermentation, are factors influencing the flocculability (floc strength) of the cells (Smit et al, 1992).…”

Section: Introductionmentioning

confidence: 98%

See 1 more Smart Citation

Quantification of brewers' yeast flocculation in a stirred tank: Effect of physical parameters on flocculation

Hamersveld

¹

,

Lans

²

,

Luyben

³

1997

Biotechnol. Bioeng.

Self Cite

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Quantification of yeast flocculation under defined conditions will help to understand the physical mechanisms of the flocculation process used in beer fermentation. Flocculation was quantified by measuring the size of yeast flocs and the number of single cells. For this purpose, a method to measure floc size and number of single cells in situ was developed. In this way, it was possible to quantify the actual flocculation during fermentation, without influencing flocculation. The effects of three physical parameters, floc strength, fluid shear, and yeast cell concentration, on flocculation during beer fermentation, were examined. Increasing floc strength results in larger flocs and lower numbers of single cells. If the fluid shear is increased, the size of the flocs decreases, and the number of single cells remains constant at approximately 10% of the total cells present. The cell concentration also influences flocculation, a reduction of 50% in cell concentration leads to a decrease of about 25% in floc size. The number of single cells decreases in linear proportion to the cell concentration. This means that, during yeast settling at full scale, the number of single cells decreases. The results of this study are used in a model for yeast flocculation. With respect to full scale fermentation the effect of cell concentration will play an important role, for flocculation and sedimentation will occur simultaneously leading to a quasi steady state between these phenomena. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 190–200, 1997.

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“…After initiation, the flocculence of the cells increases rapidly. • From the moment the cells become flocculent, the flocculability, which represents the actual floc strength under favorable environmental conditions, also increases (van Hamersveld et al, 1996). The pH and sugar concentration of the medium, which both change during fermentation, are factors influencing the flocculability (floc strength) of the cells (Smit et al, 1992).…”

Section: Introductionmentioning

confidence: 99%

Quantification of brewers' yeast flocculation in a stirred tank: Effect of physical parameters on flocculation

Hamersveld¹,

Lans²,

Luyben³

1997

Biotechnol. Bioeng.

Self Cite

View full text Add to dashboard Cite

Quantification of yeast flocculation under defined conditions will help to understand the physical mechanisms of the flocculation process used in beer fermentation. Flocculation was quantified by measuring the size of yeast flocs and the number of single cells. For this purpose, a method to measure floc size and number of single cells in situ was developed. In this way, it was possible to quantify the actual flocculation during fermentation, without influencing flocculation. The effects of three physical parameters, floc strength, fluid shear, and yeast cell concentration, on flocculation during beer fermentation, were examined. Increasing floc strength results in larger flocs and lower numbers of single cells. If the fluid shear is increased, the size of the flocs decreases, and the number of single cells remains constant at approximately 10% of the total cells present. The cell concentration also influences flocculation, a reduction of 50% in cell concentration leads to a decrease of about 25% in floc size. The number of single cells decreases in linear proportion to the cell concentration. This means that, during yeast settling at full scale, the number of single cells decreases. The results of this study are used in a model for yeast flocculation. With respect to full scale fermentation the effect of cell concentration will play an important role, for flocculation and sedimentation will occur simultaneously leading to a quasi steady state between these phenomena.

show abstract

On the Measurement of the Flocculation Characteristics of Brewers' Yeast

Cited by 11 publications

References 26 publications

Effect of Environmental Conditions on Flocculation and Immobilisation of Brewer's Yeast During Production of Alcohol-Free Beer

Effect of Environmental Conditions on Flocculation and Immobilisation of Brewer's Yeast During Production of Alcohol-Free Beer

Quantification of brewers' yeast flocculation in a stirred tank: Effect of physical parameters on flocculation

Quantification of brewers' yeast flocculation in a stirred tank: Effect of physical parameters on flocculation

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