PHYSICAL PROPERTIES OF COMMERCIAL BREWING YEAST SUSPENSIONS

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Abstract
The cell surface charge and microstructure of four commercial strains of brewing yeast were examined using electrokinetic and scanning electron microscopic (SEM) techniques. Flocculent and non-flocculent ale and larger strains were observed to possess non-normally distributed surface charges while suspended in buffers of various pH values with and without 1.0 mM calcium, 5% ethanol and 0.5 M KCl. Non-normal charge distributions were also observed when the strains were suspended in commercial ale and lager beers. During SEM examination, a number of distinct structures appeared to be involved in cell-to-cell interactions. Observed differences in cell wall microstructure and the finding of non-normally distributed surface charges indicate that these pure brewing strains possessed substantial phenotypical variation.