« on: February 28, 2015, 08:31:35 AM »
What pitching a larger number of cells does when pitching high gravity wort is allow for cell loss due to osmotic pressure. Osmotic pressure is a phenomenon that causes water to be drawn to the side of a semi-permeable membrane that has the highest level of solute, which is the wort. This loss of water causes the cells to lose something known as turgor pressure. The loss of turgor pressure is known as plasmolysis. Turgor pressure pushes the cell membrane against the cell wall. Loss of turgor pressure causes the cells to shrink, resulting in shock, if not outright death.
Interesting stuff - brings up a few questions:
1) What kind of cell loss should one expect when pitching directly from a vial, or smack-pack of commercial yeast?
2) Does the fact that you are making a starter in a wort that is lower, but approaches the OG of your beer help buffer that loss/shock?
3) The math presented, I assume, is for optimum conditions. Can we expect numbers that good for our homebrew if we add nutrients and oxygenate to a reasonable level?