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閱讀：249 發布時間：2015-6-2

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.