Comparison of Revised Yeast Counting Methods. David O. Schisler, Adolph Coors Company, Golden, CO 80401. J. Am. Soc. Brew. Chem. 44:0081, 1986.

Experiments were conducted on three yeast counting methods to improve each method's accuracy and reproducibility. The revised methods were evaluated comparatively on a set of samples that provided a wide range in yeast density. Results for each method demonstrated linearity across the range of samples tested. However, results for a given sample were highest using the microscopic method. Counts obtained with the Coulter Counter TAII were approximately 18% lower than microscopic counts, and plate count results were approximately 28% lower than microscopic counts. Both the microscopic and electronic counting methods demonstrated excellent reproducibility, as evidenced by coefficients of variation of 2.0 and 1.1%, respectively. By comparison, the plate count method produced a coefficient of variation of 12.5%. Based upon these findings, the revised microscopic counting method is the most reliable and practical of the methods and instruments tested for assessment of yeast densities.

Keywords: Coulter Counter, Hemacytometer, Microscopic counts, Plate count, Yeast