Effect of the Concentration of Propagation Wort on Yeast Cell Volume and Fermentation Performance

Cahill, Gearoid; Murray, Deirdre M.; Walsh, Padraig K.; Donnelly, Dan

doi:10.1094/asbcj-58-0014

Cited by 18 publications

(27 citation statements)

References 8 publications

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“…This was because sparging was not possible due to the lack of a filter bed. In terms of the fermentation performance, although yeast counts were somewhat high 8 , all other fermentation parameters were found to be normal 33 .…”

Section: Discussionmentioning

confidence: 90%

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Processing of a Top Fermented Beer Brewed from 100% Buckwheat Malt with Sensory and Analytical Characterisation

Phiarais

Mauch

Schehl

et al. 2010

Journal of the Institute of Brewing

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A top fermented beer was brewed from 100% buckwheat malt and sensory and analytical characterisation was carried out. Difficulties with lautering and filtration were encountered during the brewing process, which resulted in problems during fermentation and beer filtration. The beer was evaluated in the fresh and forced aged state for the following attributes: odour, purity of taste, mouthfeel, tingling, and bitterness. Analytical results indicated that the buckwheat beer compared quite closely to a typical wheat beer with regard to pH, FAN, fermentability and total alcohol. However, the extract of the buckwheat wort was lower, resulting in a final extract yield of 54.5%. GC analysis of the resultant beer revealed commonly encountered levels of the esters that give beer a fruity character. A low level of fusel alcohols, in comparison to a typical wheat beer, was detected. A high level of ethyl caprinate (coconut flavour) and lauric acid (fatty odour) was detected. Sensory analysis indicated that the buckwheat beer was acceptable with regard to odour, purity of taste, mouthfeel, tingling and bitterness. In conclusion, results of this study prove buckwheat's qualification as a gluten-free brewing material and with process optimisation, its readiness for marketing.

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Section: Discussionmentioning

confidence: 90%

“…Yeast is often pitched at a rate of 6.30-6.60 log CFU mL -1 into wort 8 . Although manufacturer's instructions were followed, results showed a pitch rate of 7.73 log CFU mL -1 (Table III) which exceeded the recommended pitching rate.…”

Section: Yeast Cell Count (Cfu ML -1 )mentioning

confidence: 99%

Processing of a Top Fermented Beer Brewed from 100% Buckwheat Malt with Sensory and Analytical Characterisation

Phiarais

Mauch

Schehl

et al. 2010

Journal of the Institute of Brewing

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“…They provided evidence that increases in wort osmotic pressure produced shrinkage in the yeast cells. Additionally, Cahill et al 4 also observed decreases in cell volume when yeast cells were exposed to varying concentrations of osmotic stress. The findings indicate that osmotic stress has a more marked effect on the mean cell volume of the lager strains than ale strains studied.…”

Section: )Jjigx Sj Swqsxmg Wxviww Sr Qier Gipp Zspyqi Sj Pekiv Erh Epmentioning

confidence: 96%

“…The analytical method employed to determine yeast cell volume was a modification of the method reported by Cahill et al 4 . Microscopic images of diluted yeast samples were recorded using a JVC KY-F55B colour video camera (Victor Company of Japan Ltd., Yokohama, Japan) attached to a Zeiss Optiphot microscope (Zeiss, West Germany) at 400× magnification.…”

Section: LI Hixivqmrexmsr Sj ]Iewx Gipp Zspyqi Hyvmrk Jivqirxexmsr Ymentioning

confidence: 99%

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The Effects of Osmotic Pressure and Ethanol on Yeast Viability and Morphology

Pratt

Bryce

Stewart

2003

Journal of the Institute of Brewing

102

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The selection of a brewing yeast strain with the required fermentation and recycling characteristics is critical. The yeast strain will influence the rate and extent of fermentation, the flavour characteristics and the overall quality and stability of the finished beer, and consequently, the economic viability of the brewery. Since high gravity worts can have a deleterious effect on yeast fermentation performance, it is imperative that the strain selected be suitable for this environment, which includes a capacity to withstand high osmotic pressures and elevated ethanol levels. Under controlled in vitro osmotic and ethanol induced stresses, there was a decline in mean cell volume in both lager and ale yeast strains. Whilst significant reductions in viability were observed in the lager strains, the ale strains studied were not affected. Cell surface investigations revealed shrinkage of the yeast cells and crenation of the outside envelope under both stresses, although exposure to ethanol had a more marked effect on the yeast cell surface than sorbitol-induced elevated osmotic pressure.Key words: Cell viability, cell volume, ethanol, high gravity wort, osmotic pressure. -2863(9'8-32In brewing, yeast is recycled and the fact that it is cropped and repitched into subsequent fermentations is one of the differentiating features between brewing and the production of many other alcoholic beverages including Scotch whisky 37 . Consequently, the quality of yeast cropped will not only affect the overall performance of most fermentations but also the quality and stability of the resulting beer. It is important therefore that the factors which influence yeast performance in the brewing process, and particularly in high gravity brewing, are considered, to ensure efficient fermentation and the production of a beer of a consistently high quality and stability. Breweries, the world-over, are continually seeking ways to reduce capital expenditure, labour, utilities, effluent and other operational costs and at the same time ensuring that the quality of their beers remains consistently high. As a result, many are employing the process of high gravity brewing due to its many advantages 39 . Similarly, some breweries have not implemented this process due to its disadvantages 40 . Of significance, are the deleterious effects of this process on yeast fermentation performance 41,43 . Fermentations have been reported to be sluggish due to elevated ethanol levels and high osmotic pressure, resulting in yeast viability and vitality reductions 6 . Osmotic pressure is the force that develops between two solutes of differing concentration separated by a semipermeable membrane 20 . When yeast is exposed to wort it is subjected to an osmotic pressure. Very high osmotic pressures such as those encountered in high gravity worts, may distort yeast metabolism or decrease yeast viability. The extent of the osmotic pressure will depend on the concentration of solutes surrounding the cell 20,23 . It has been shown that increases in wort osmotic pressu...

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Determination of yeast glycogen content by individual cell spectroscopy using image analysis

Cahill¹,

Walsh²,

Donnelly³

2000

Biotechnol. Bioeng.

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Effect of the Concentration of Propagation Wort on Yeast Cell Volume and Fermentation Performance

Cited by 18 publications

References 8 publications

Processing of a Top Fermented Beer Brewed from 100% Buckwheat Malt with Sensory and Analytical Characterisation

Processing of a Top Fermented Beer Brewed from 100% Buckwheat Malt with Sensory and Analytical Characterisation

The Effects of Osmotic Pressure and Ethanol on Yeast Viability and Morphology

Determination of yeast glycogen content by individual cell spectroscopy using image analysis

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