Yeast Counting for Homebrewers Or It Surely Beats Counting Sheep* Copyright 2004 HBD
				Many of us have stood agog while others around us spoke of how many cells per milliliter they were pitching into their beers. Felt left out, Binky? Well, feel left out no more! Professor Frothinphome is here to the rescue! There’s nothing tough or mysterious about counting yeast cells. You just need some equipment and a technique (or really, really strong glasses). Listen up, class – this will be on the final!
	What you'll need: Hemocytometer Slip Cover Pipette Microscope Flask What to do: First, make sure EVERYTHING is clean and dry. Put a two milliliters of the liquid you wish to count yeast from in the flask. Add 18 ml of distilled water. Swirl it around to break up any clumps of yeast and to get any gas out of solution. Put the slip cover on the hemocytometer so that it covers both counting areas. Pull a few milliters of the sample from the flask using the pipette. Touch the tip of the pipette to a paper towel, then, with the slip cover in place on the hemocytometer, put the pipette on the one of the v-notches of the hemocytometer and fill the associated counting area. Fill it all the way up, but be careful not to overfill it! If you overfill it, it will look like it is bulging at the canals which surround the counting areas (if you REALLY over fill it, it will flow into the canals...). Only a drop or two will fill it. Place the hemocytomer onto the microscope stage - careful not to lose any of your sample! Now, count the cells in the four corner counting squares and in the center grid. Multiply by 5 (if you prefer, you can count the cells in all of the 25 counting squares - if you do, don't multiply by 5!). Now, multiply by 10 (the dilution factor) and by 10,000. The result will be the number of cells per milliliter you can expect. This is a statistical process - the number you get will not be the actual number of cells per milliliter in the physical solution, but is a "good enough" estimate by most standards... Of course, there are things you can do to enhance its predictive ability. Develop a “standard” for what you will or will not count in terms of where a cell lays on the counting grid, or the stage of budding a cell may be in. Once you set such a standard, BE CONSISTENT! This will keep you from having wild variations between countings. The reference sites cover this in much more detail – plus, they give you methods for determining yeast viability. Surf on, Brewer! For more info, see: http://www.brewingtechniques.com/library/backissues/issue2.4/allen.html http://www.whitelabs.com/cell_count.html http://www.dbs.ucdavis.edu/courses/s01/mic102l/files/209.pdf http://www.users.fast.net/~dwhitman/yeast/experime.htm *Contrary to established opinion, I have never pitched a sheep into my wort.