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Yeast Physiological State Influence on Beer Turbidity
閱讀：255 發(fā)布時(shí)間：2015-6-2| 提 供 商 | 美國(guó)布魯克海文儀器公司 | 資料大小 | 301.9KB |
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The physiological state of yeast affects the intensity of propagation and biosynthesis
of secondary metabolites and determines the sensory profile of beer. Besides that, yeast with
low physiological activity increases the number of colloidal particles in beer, which consist of
proteins and polysaccharides. The purpose of this study was to select a method for assessing the
physiological state of yeast and to study the influence of yeast physiological state on the
adsorption of compounds that determine the colloidal stability of beer. As a result of
comparative analysis of different methods for determining the non-viable and weakened cells
with dyes a certain correlation between them was found. The highest correlation (R2 = 0.84) was
set between parameters obtained by staining yeast cells by methylene blue with Safranin O,
which stains both dead and weakened cells and dihydrorhodamine 123, which detects only
physiologically least active yeast. Sufficiently high correlation (R2 = 0.83) was observed when
cells were stained with methylene blue, which identifies only dead cells, and with methylene
blue with Safranin O. The worse the physiological condition of yeast, the less they adsorb
turbidity-inducing compounds, so more substances remain in beer, reducing its stability. Thus,
the increase in the proportion of damaged and non-viable cells from 24.2 to 32.2% leads to
increased beer turbidity from 1.5 to 3.3%. Z-potential of yeast cell walls determines their
sorption properties. Physiologically active yeast cells are able to adsorb positively charged
colloids due to the negative charge of their surface. Activation of the yeast’s surface potential
occurs in the presence of oxygen.