VIEW ARTICLE    DOI: 10.1094/ASBCJ-53-0174

Towards an Ideal Flocculation Assay (1). R. Alex Speers (2) and L. L. Ritcey, Department of Food Science and Technology, Technical University of Nova Scotia, P.O. Box 1000, Halifax, NS B3J 2X4. (1) Presented at the ASBC Annual Meeting, Toronto, Ontario, Canada, May 1994. (2) Formerly at the Department of Food Science, Acadia University, Wolfville, Nova Scotia, Canada. J. Am. Soc. Brew. Chem. 53(4):174-177, 1995. Accepted May 2, 1995.

Yeast flocculation has been and continues to be an active area of brewing research with over 75 articles published since 1984. In spite of this activity, there is no internationally established method of quantification of the degree or rate of yeast flocculation. Partly due to the lack of a quantitative assay and use of present, empirical-based methods, the literature contains various controversies. The lack of a simple yet quantitative assay is hindering our understanding of this important phenomenon. In this article, the flocculation assay methods in current use will be summarized, and important factors that one must consider when devising a flocculation assay will be discussed. Such factors include influences of the suspension media such as pH, osmolatity, ionic strength, and individual ion concentrations. In addition, yeast flocculation rates are influenced by physical factors such as the rheological and laminar or turbulent flow behavior of the suspending medium, cell size and cell shape, as well as other colloidal aspects. We have outlined an assay method in the hope that it will serve as a prototype for development of an "ideal" flocculation assay. Keywords: Aggregation, Brewing yeast, Flocculation assay