Yeast Counting by Microscopy or by Electronic Particle Counting. K. J. Siebert and T. J. Wisk, The Stroh Brewery Co., Detroit, MI 48226. J. Am. Soc. Brew. Chem. 42:0071, 1984.

Although the fundamental property determined with an electronic particle counter is different from that determined microscopically, results that are similar to those produced by microscopic counting can still be obtained. Microscopic counting is most straightforward for yeast samples that do not contain many cell clumps or buds. Operating conditions for the electronic particle counter (Coulter Counter®)² were systemically examined, and control settings were chosen that produced results in agreement with those of microscopic counting for yeast that was not actively growing. Ultrasonic energy and treatments with pepsin and ethylenediamine tetraacetic acid can be used to separate clumps of yeast cells. The effects of sonicator energy level and treatment time were also studied. Early in fermentation, the Coulter Counter produced lower results than did microscopic counting; this difference was directly related to the number of yeast cell buds present. Electronic particle counting is much faster and much more precise than microscopic counting.

Keywords: Electronic particle counting, Enumeration, Ultrasonic treatment, Yeast buds, Yeast clumps